Downtown Doug Brown

In my last post about hard drives that go bad over time, I hinted at having rescued a lost piece of obscure Apple software history from an old 160 MB Conner hard drive that had its head stuck in the parked position. This post is going to be all about it. It’s the tale of a tad bit of an obsession, what felt like a hopeless search, and how persistence eventually paid off. There’s still an unsolved mystery too, so I’m hoping others will see this and help to fill in the blanks!

This whole saga starts with a very interesting blog post written by Pierre Dandumont in 2022. Pierre’s (excellent) blog is in French — Google does a good job of translating it for me. He found a quote in a book referring to special functionality bundled with Apple’s Macintosh Performa 550 computer:

The LC 550’s Secret Partition

If Apple’s programmers, in creating the Performa series, were aiming to make idiot-proof computers, they were serious about it. The Performa 550 is an amazing case in point. When you run the included Apple Backup program (see Chapter 15), you get a little surprise that you didn’t count on: a hidden partition on your hard drive!

This invisible chunk of hard drive space contains a miniature, invisible System Folder. Apple’s internal memo explains it this way:

“When a system problem (one that prevents the Performa from booting) is detected, a [dialog box] informs the user of a system problem. The user can choose to fix the problem manually or to reinstall software from the backup partition’s Mini System Folder.”

If you choose to reinstall your System software, you get the wristwatch cursor for a moment while the miniature System Folder is silently copied to your main hard-drive partition. The Performa restarts from the restored hard drive, and the invisible system partition disappears once again.

We got a Performa team member to admit that this kind of sneaky save-the-users-from-themselves approach may well be adopted in other Performa models.

Who knows what goodness lurks in the hearts of men?

Cool! Although I have owned my own copy of this book for decades, I had no recollection of ever reading this little blurb. The book, if you’re curious, is Macworld Mac Secrets by David Pogue and Joseph Schorr. I found this whole functionality very intriguing, particularly because I had what felt like a very personal connection to it: the very first Mac that my family had when I was growing up was a Performa 550. I don’t think I have any pictures from back then, but in the meantime I’ve acquired one that looks exactly identical, so here’s a (slightly blurry) view of the type of machine I’m talking about in this post:

I know that many people think the LC/Performa 5xx case style is ugly, but I really like it! I’m definitely biased though.

This is an early model manufactured in September of 1993, which came with a caddy-loading CD-ROM drive (AppleCD 300i). Like other Macs from the same era, newer versions from 1994 came with a tray-loading drive instead (AppleCD 300i Plus). For comparison, here’s a photo of a late-model Performa 550 with a manufacture date of March 1994 that re4mat kindly gave me permission to share here:

Pierre asked me if I had a copy of Apple’s software restoration CD for the Performa 550, and if I knew how to get it working in an emulator in order to try out this special functionality. I pointed him to a download link for the Performa CD for the 500 Series, version 7.1P6:

If you weren’t using multimedia computers in the early 1990s, you might not recognize the weird rectangular container that this CD is enclosed inside of. It’s a CD caddy, and it’s what was used for inserting CDs into computers like the first one pictured above. You would open the caddy by squeezing the top right and bottom right ends toward each other, stick the disc into it, close it, and then push it into the slot in the computer, similarly to how you would insert a floppy disk. I really don’t miss these things one bit!

Back to the story, though. I also gave Pierre some tips for using the restore CD in an emulator. Nowadays, my advice is outdated because it’s much easier to use Apple restore CDs in at least one emulator — MAME has come a long way in the last few years. He figured out a bunch more stuff on his own after that, including trying it in his own Performa 450 (not 550), but the bottom line was that the recovery partition was nowhere to be found.

Well, sort of. He found that the process of restoring from the CD actually did create a recovery partition. Here’s a screenshot of the partitioning from inside of Apple HD SC Setup while booted from the Performa CD, after formatting the hard drive by clicking the Initialize button in the main window:

As you can see, there’s a 2,560 KB partition of type Apple_Recovery almost at the end of the drive, just after the main partition named “Hard Disk”. This was promising at first glance, but the partition was empty! Further testing revealed that the custom Performa-specific version of Apple HD SC Setup (7.2.2P6) bundled on the CD was responsible for creating it, but didn’t actually populate it with any data. Apple Backup also didn’t put anything onto the partition, despite what the book said. I even looked through my past disassemblies of the Apple Backup and Apple Restore code and confirmed that there was nothing related to creating a recovery partition.

The conclusion at the time was that someone needed to get ahold of a Performa 550 that still had its original hard drive and had never been reformatted. That’s where this story sat for 3 years.

A few months ago, I remembered this whole situation and decided that I really wanted to try to find this partition. After all, the clock had always been ticking. The longer we waited, the fewer and fewer original Performa 550s would be out there in the wild. Not to mention that hard drives go bad and people throw them out without knowing that it’s usually possible to recover data from drives of this era. I confirmed all of Pierre’s findings in MAME. I even tried using Apple Backup in case I missed something, but no, it didn’t do anything with the hidden recovery partition. An easy way to look at it is to manually edit the partition table in a hex editor and change the type from Apple_Recovery to Apple_HFS.

After doing this and booting up, I found another hard drive icon on my desktop called Recovery Volume, but it was empty, just like Pierre said:

Taking it a bit further, I tried recreating the recovery functionality myself. I copied a minimal system folder to the Recovery Volume, and then changed its type back to Apple_Recovery. This made it invisible again. Then I screwed up my main system folder and rebooted. Sure enough, it automatically came up with the Recovery Volume as the main boot volume.

This proved that the mechanism for booting from the recovery partition worked; we were just missing the data that was supposed to be on it. I came to the same conclusion that Pierre had already reached: we needed to find a Performa 550 that had never been reformatted. In the meantime, I spent some time digging into archives of Apple’s old tech notes and found several more references to this functionality.

System 7: Performa Versions Compared (9/95) — the first bullet point under System Software Version 7.1P6 refers to this feature:

Backup Partition Software-automatically detects corrupted system folders. When a bad System Folder is detected, the user is given the option to re-load another System Folder into their system.

Performa 550: Description of Backup Partition (3/94) — this note is clearly the “internal memo” that Macworld Mac Secrets was quoting. Some interesting excerpts from this article:

The Apple Backup application creates a backup recovery partition that allows the Performa to boot even when the System Software on the main hard drive has been corrupted. The partition is invisible to the user.

There is no built-in limit to the number of times the backup partition can be used. However, the partition will be lost if the hard drive is re-formatted. At this time the backup partition is used only on the Performa 550.

Performa 550: System Folder Created w/ Dinosaur Safari CD (8/94) — not that I needed any more proof of the recovery partition’s existence at this point, but I got a kick out of this one. It talks about how launching an educational game about dinosaurs accidentally caused the system to go into recovery mode. It provided a little more info about what would happen when the recovery dialog popped up:

When I launch the Dinosaur Safari CD from Creative Multimedia, a dialog box appears telling me that my Performa computer is having trouble starting up. I only have two options Shutdown or Continue? Why?

After reading these articles, I was very convinced that the recovery partition was a real thing that existed, but I was also pretty confident that Apple Backup wasn’t responsible for creating it, despite Apple claiming otherwise. I had already seen that the special build of Apple HD SC Setup was what actually created it, and plus, like I said earlier, I had looked closely into a disassembly of the version of Apple Backup supplied with the Performa 500 series restore CD. There was nothing that copied any files to another partition on the hard drive, at least not that I could see.

Really, the most important thing I gained from this exercise was that the second tech note confirmed the need to find a Performa 550 that had never been reformatted. Also, if the first tech note was to be believed, it needed to have come with System 7.1P6. This could narrow the search even further — I know for a fact that earlier Performa 550 models came with 7.1P5, including my childhood one. The same tech note also pointed out that 7.1P6 was the first version to support the “AppleCD 300+”, which is referring to the tray-loading CD-ROM drive. Based on this information, it’s reasonable to deduce that all Performa 550s with a tray-loading CD-ROM drive would probably have originally come with at least System 7.1P6.

There was only one thing left to try at this point: asking the Internet for help. I asked people everywhere I could think of: Tinker Different, 68kMLA (where Pierre had already asked), and various social media sites. I searched Reddit and found people who had posted in the past about having a 550, asking if they still had the hard drive. I think I scared some of them — at least one person deleted their post after I asked! To be honest, I can’t blame them. I can imagine how freaky it would be to hear from someone begging to look at my hard drive’s contents. I’m sure some people might think of it as crossing a line, but it’s not as crazy of an ask if it’s a machine they’ve received second-hand from someone else. Plus, I was very clear about exactly what I was looking for (and why).

I asked a seller of a Performa 550 that had been sitting on eBay for a long time if they would be willing to sell me the hard drive separately. They weren’t interested. I even bought some random hard drives on eBay that definitely went with a 5xx-style case. These were easy to identify because this case style uses a unique adapter for plugging the drive into the chassis wiring harness when you slide it into place.

What do I have to show for all of these eBay purchases? Well, after dumping them all with my ZuluSCSI in initiator mode, I can say that the one pictured above came from a Macintosh TV. I also found another one from an LC 575. Lastly, I bought yet another drive that the seller said came from a Performa 577. The Performa 577 one was funny — it had all the Mac mounting hardware on it, but when I dumped it, it turned out to be from an Atari TT or Falcon (not sure which). I’d love to hear the story of how it ended up with an LC 5xx drive sled and adapter on it! Needless to say, none of them had the elusive recovery partition. One particularly friendly eBay seller was even nice enough to show me a preview of a drive’s contents in HFSExplorer, which helped me determine that it wasn’t from a Performa.

I almost began questioning my sanity at one point during this search. Multiple people initially told me that they thought I was confused about this whole thing. I pointed them toward Apple’s tech notes describing it. Were Pierre and I imagining this whole thing? Were Apple’s tech notes all a lie?

The thing is, this whole functionality was super obscure. It’s understandable that people weren’t familiar with it. Apple publicly stated it was only included with this one specific Performa model. Their own documentation also said that it would be lost if you reformatted the hard drive. It was hiding in the background, so nobody really knew it was there, let alone thought about saving it. Also, I can say that the first thing a lot of people do when they obtain a classic computer is erase it in order to restore it to the factory state. Little did anyone know, if they reformatted the hard drive on a Performa 550, they could have been wiping out rare data that hadn’t been preserved!

Someone who saw my post on Reddit mentioned that they had a Performa 550 and would check it out. It was a newer tray-loading model with a January 1994 manufacture date. Unfortunately, the Conner hard drive inside of it wouldn’t cooperate, and plus this person didn’t have anything capable of dumping the contents. Luckily for me though, they were totally comfortable with letting me borrow the drive and try to recover the data from it.

To tie everything together, we have now reached the point in this story that I covered in my last post about hard drives with stuck heads. As I mentioned in that blog, I could not get this drive to do anything. It would just spin up, sit there for a while, spin down, and then make an annoying buzzing sound for a while, repeating that whole process over and over again.

I tried all kinds of things. I nudged the head while the platters were spinning, inspected it with my thermal camera to see if any components were getting hot, and tried it at different temperatures — cold shortly after it arrived, and at room temperature later. The only thing I noticed was that when it was making the buzzing sound, one of the IRFD123 MOSFETs would get much hotter than normal: up near 100 degrees Celsius.

I wasn’t really sure what to do with this information though. It just seemed wrong that the head wasn’t moving at all. That’s when I finally decided to inspect everything further inside the drive and noticed the head stack seemed like it was sticking to a rubber/plastic looking piece. The Kapton tape trick I figured out and showed off in the last post finally allowed me to dump the drive contents. If you didn’t catch it last time, here’s a video showing how it was stuck, along with a successful dump with the help of the tape:

As soon as the drive imaging process completed, I powered everything off and anxiously opened the hard drive image file with my favorite hex editor (HxD):

Boom! This drive had a recovery partition on it! Now, that didn’t necessarily mean anything. After all, I had already seen an empty partition created by Apple HD SC Setup on the Performa CD. Still, though, it was definitely promising. Here’s an interpretation of the data at the beginning of the entry in the partition table:

50 4D = PM = Signature
00 00 = Padding
00 00 00 05 = 5 total partitions on the drive
00 04 E2 60 = starting physical block of the partition (0x4E260 blocks = 0x9C4C000 bytes)
00 00 14 00 = size of partition in blocks (0x1400 blocks = 0x280000 bytes = 2560 kilobytes)
name = MacOS
type = Apple_Recovery

Also, just like in the partition table created by the Performa CD that I had inspected earlier, there were four bytes “msjy” at an offset of 0x9C bytes into the partition table entry. No other partitions had any data at 0x9C. I wonder if these are a couple of developers’ initials hiding in there or something? Is it an acronym? “Make Steve Jobs Yodel”? I even asked ChatGPT to come up with a playful interpretation in the context of Macs in the mid-1990s. It suggested “My System Jammed Yesterday”, explaining it as a playful nod to the “chaotic charm” of the era’s extension conflicts and Sad Mac screens. I didn’t even mention anything about it involving OS recovery. Tell me how you really feel about old Macs, ChatGPT!

Knowing that the partition was there, the next step was to look near the end of the dumped drive image in HxD. If the partition had any actual data stored, it would be very obvious because starting at 0x9C4C000 in the file, there would be actual data and not just a bunch of zeros.

This is where I started to actually get excited. The partition contained boot blocks! This was obvious because of the starting signature of LK and all of the various system file names plainly visible. On the other hand, the recovery partition created by the Performa CD during testing had zeros at this location — no boot blocks.

These boot blocks are identical to the main partition’s boot blocks, except for one very important difference: at 0x1A, the Pascal string containing the Finder name is “recovery” instead of “Finder” like you’d normally see. This means that if you boot from this partition, it will load a program named recovery instead of the usual Finder app you’d expect on most Mac OS installs.

This was definitely something special that the restore CD was not capable of recreating. As I scrolled further down through the partition, it quickly became obvious that it actually had some files!

Okay, now I was totally stoked! I booted up a copy of the imaged drive in MAME and immediately noticed that there was evidence that the recovery partition had definitely activated itself on this machine in the past: there was a folder named Mini System Folder on the desktop with a creation date in 2004, and the trash contained an app called Read Me Mini System Folder with the exact same date.

I wanted to experience the automatic OS recovery process for myself without any customizations from the original owner of the machine this hard drive came from, so I used HxD to copy the entire 2,560 KB recovery partition onto the fresh hard drive image I had created by restoring from the Performa CD. This was easy because the Performa version of Apple HD SC Setup had created an empty recovery partition with the exact same size. Then I booted it up in MAME and dragged the System file out of my System Folder in order to intentionally mess it up. I had to turn off System Folder Protection in the Performa control panel first:

This is the classic kind of mistake that would have normally left you with an unbootable system showing a floppy disk icon with a flashing question mark. Would Apple’s automatic Performa OS recovery save me from myself? I rebooted to see what would happen. Instead of seeing a flashing question mark, I saw a Happy Mac very briefly before the system rebooted itself again. Then another Happy Mac showed up, and this time, it looked like a normal boot, except no extension icons showed up at the bottom of the screen. It was definitely booting from the recovery partition. Eventually, I was greeted with this screen:

Hooray! This was exactly the dialog box that Macworld Mac Secrets and Apple’s tech note had referred to. The recovery partition had been successfully rescued!

Let’s walk through the rest of this feature. If you click Shut Down, obviously the machine turns itself off. But when it boots back up, the recovery partition doesn’t automatically kick in anymore. So you’re on your own to fix the problem by booting from the Performa CD or the Utilities floppy disk.

On the other hand, clicking OK does exactly what the tech note describes. You get the wristwatch cursor for a few seconds, the system reboots, and then you are greeted with this amazing screen, complete with an ugly yellow desktop pattern. Shall we call it the yellow screen of shame? Notice that the Mini System Folder on the desktop is the active System Folder, because it has the special icon.

Here are the rest of the pages in this Read Me Mini System Folder app:

Aha! So it’s not entirely automatic, since you still have to manually drag the System, Finder, and System Enablers from the Mini System Folder back to your original System Folder. Still though, it’s a very handy solution that gives you a bootable machine when something goes wrong with your OS.

If you just ignore these instructions and keep using the computer, you will be nagged with this Read Me on every boot because it lives inside the Startup Items folder of the Mini System Folder. The Read Me also appears on your desktop, but for some reason it doesn’t show up until you open the Hard Disk icon.

Let’s take a deeper look at how it all works by temporarily changing the partition type to Apple_HFS instead of Apple_Recovery and booting up again, so we can inspect the files. After a quick automatic rebuild of the desktop file, the Recovery Volume appears, with actual contents this time!

Inside of the System Folder, there are definitely some interesting things. As expected based on the earlier analysis of the boot blocks, there is an app named “recovery” that contains all of the interesting stuff. The icons are kind of arranged willy-nilly in here.

The creator code of the recovery app is msjy — the exact same magic value we saw in the partition table entry.

Scrolling further down, there is a System file and various enablers. Everything is marked as being part of System Software v7.1P6.

It’s interesting to me that although this recovery partition was only available on the 550, it still has a bunch of enablers for other Performa models: the 45x/46x, 47x/57x, and 600. I guess that’s not too crazy considering all of these exact same enablers are included with a fresh copy of System 7.1P6 installed using the Performa CD.

As a quick detour, System Enabler 316 is an interesting one that is hard to find info about on the Internet. I inspected its ‘gbly’ resource and determined that it’s for the Centris 610, Centris 650, and Quadra 800. It’s an older version of the enabler created before the speed-bumped Quadra 610 and Quadra 650 were a thing. I wonder if there was a plan at some point to have a Performa model based on one of those machines? If I had to guess, maybe it would have been a 68040-based successor to the Performa 600, which uses the same case style as the Centris 650. The Performa 650?

Let’s not get too far off track. Back to the Recovery Volume’s System Folder — as expected, the Startup Items folder contains the Read Me application:

Everything started to become clear. The recovery app was marked as the startup application instead of the Finder. It displayed the dialog giving the user the option to recover. If they clicked OK, it would copy the entire System Folder from the Recovery Volume, omitting itself, to the Desktop Folder of the main hard drive partition. Then, it would “bless” the newly-copied mini System Folder and reboot.

How did all this stuff get into the partition? Did Apple Backup do it, or was it factory-programmed data? I tried to see if I could deduce anything from the dates of the files. In order to preserve the integrity of all of the displayed dates, I performed this analysis with a read-only copy of the original drive image in order to prevent any modification dates from being updated.

All of the files in the partition have a creation date of March 4, 1994 — over 31 years ago! Most of the files have a matching modification date, except for the System suitcase, which was last modified on September 26, 1994. I don’t know exactly what this all means, considering it came from a machine with a January 1994 manufacture date.

The Recovery Volume itself also has a creation date of March 4th, just five minutes before the creation date of all the files. Interestingly, the modification date of the volume is still shown as March 4th in the Get Info window, even though the System suitcase was modified later in September of that year.

The Master Directory Block of the Recovery Volume says the modification date (drLsMod) is September 26th, matching when the System file was changed. I’m not sure what causes this discrepancy. I guess the date displayed in the Get Info window isn’t simply the date stored in the Master Directory Block.

Similarly, although the main hard drive partition has a creation date of December 5, 1993 according to the Master Directory Block, the Get Info window says it was created on February 3, 1994. I’m not sure which one is more accurate. Either way, it’s pretty clear this drive had not been reformatted. I did find it curious that the recovery partition was created over a month later, though. When you reformat a hard drive using the special version of Apple HD SC Setup on the Performa CD, the recovery partition ends up with a creation date about a minute after the main partition.

The Finder and System Enablers in the recovery partition are identical to the same stock files from a 7.1P6 restore. The only difference I could find in the System file was that the recovery partition’s version was missing a single At Ease ‘INIT’ resource, but the At Ease Startup extension automatically adds it to the System file after you reboot. This leaves you with a System file totally identical to what is restored from the Performa CD. I find it odd that At Ease was stripped out, but the American Heritage Dictionary ‘FKEY’ resource was not.

The best theory that I can come up with is that Apple Backup really was responsible for creating this partition. After all, Apple went out of their way to specifically mention it in their tech note. Maybe March 4th, 1994 was the date when the original owner of the computer backed it up for the first time. September 26th could have been the last time that Apple Backup was run. Perhaps the owner completely uninstalled At Ease from the computer between March and September, so the System file had been changed and the recovery copy needed to be updated accordingly? Unfortunately, most of the Performa-specific software had been deleted from this computer. It was still running System 7.1P6, but Apple Backup was nowhere to be found. So I wasn’t able to confirm whether or not a mysterious, unpreserved newer version of Apple Backup was really responsible for populating the partition.

The other theory floating around in my head is that maybe it came from the factory like this. The March 1994 timeline is consistent with the date of the tech note describing the functionality, so maybe that’s when Apple created it and started bundling it. I don’t know how long the machines sat at Apple’s factory before they were actually sold — does a manufacture date of January 1994 also mean it was shipped to a store in January 1994? Either way, I definitely don’t know how to explain the September 26th, 1994 modification date. Maybe a third-party utility did something to the System file on the secondary partition? The first Apple Backup theory seems like the more likely explanation, especially given that Apple said that’s how it was created.

This whole question is the last piece of the puzzle that hasn’t been solved yet. If anyone else has a Performa 550 and would be willing to dump their hard drive or at least look at Apple Backup, I’d be very interested in finding out A) if it has the recovery partition and B) if there was a special newer version of Apple Backup that didn’t make its way onto the Performa CD. I searched for various strings that show up in the “recovery” and “Read Me Mini System Folder” apps, and they aren’t anywhere on the Performa CD. I guess they could be stored compressed somewhere, but I’m pretty confident based on the actual Apple Backup code that nothing is hiding in there. Here are the various versions (with their exact sizes and dates) of Apple Backup that I have seen on Performa 550 installations. None of these have the recovery partition creation built in:

I also found version 1.3 (June 15, 1994, 163,388 bytes used) by restoring from a Performa 636 restore CD. It, too, does not contain any recovery partition code.

For a demo, I thought it would be fun to replicate the problem that the Apple tech note mentioned about the Dinosaur Safari CD inadvertently activating the recovery partition, so I bought a copy to test it out. To make it even more interesting, I decided to run this test on real hardware. I’m leaning toward believing that a lot of the older caddy-loading models (possibly all of them) didn’t have this recovery partition, so just pretend it’s a newer model that came with System 7.1P6. I copied the recovery partition onto a real Apple-branded IBM 160 MB SCSI hard drive using ZuluSCSI’s USB MSC initiator mode, which allows it to act as a USB-to-SCSI bridge. Sorry about the flickery screen; I couldn’t get my phone camera’s shutter speed to sync up perfectly with the display’s refresh rate.

Sure enough, when I opened the game from the CD, the computer did exactly what Apple’s tech note said it would do. The workaround of copying the application to my hard drive worked just fine. If it’s not obvious, I sped up the process of copying it to the hard drive — it took a while! It might be interesting someday to look into why this game accidentally activated the OS recovery, but this blog is already getting way too long!

I want to talk a little more about the yellow screen of shame. When I first saw it, I wasn’t entirely sure if it was really part of the recovery functionality or if the original owner just had terrible taste.

Digging deeper, I found three clues that all made it clear it was an intentional choice by Apple to really make it obvious that something was wrong. First, the yellow pattern is stored as a ‘ppat’ resource in the recovery app.

Second, the System file in the recovery partition has the default blue-gray Performa background shown in the screenshots above. This makes sense, because it’s the pattern that showed up with the dialog about the Performa having trouble starting up.

And lastly, page 3 of the Read Me app implies that something may have changed your desktop pattern.

So clearly, the recovery process, by design, sets up the custom yellow background.

Why did I care so much about finding this lost partition? Well, there are a number of reasons. For one, this is exactly the kind of research project that’s perfect for me because I don’t know how to let things go. It’s also something that, quite frankly, needed to be preserved before it became extinct. The most important reason, though, is that this functionality is historically significant and deserves some attention. How many personal computers in 1994 still had the ability to boot after the OS was trashed? Isn’t this an extremely early example of this type of functionality? Did Windows have anything like this prior to Vista? Did the Mac have anything else like this prior to sometime in the OS X era? I would love to hear more comments about what you think on this. I admittedly don’t know a ton about older machines that weren’t Macs.

I’m not saying this feature is perfect. Since we’ve already seen that the Dinosaur Safari CD was able to accidentally activate it, I wouldn’t be surprised if there were other ways to inadvertently cause it to pop up too. It also required manual intervention after the recovery process, which meant that you needed a fair amount of computer knowledge to finish fixing your OS. The average Joe Schmoe would probably have trouble following these directions to fix the System Folder. But still, it leaves you with a bootable system instead of an unusable computer with a flashing question mark. It’s very cool, especially for 1994.

I wonder why Apple didn’t continue down this path with subsequent models? Or even retroactively adding the functionality to earlier ones after a fresh install of a newer OS. I’m not aware of any other Macs that have this partition. It doesn’t depend on any special ROM support or anything like that, at least as far as I can see. I tried out the recovery functionality on several other machines: a IIci, LC, LC 475, and an emulated Performa 600, and it works great on all of them. Heck, it even works on the Classic II/Performa 200!

It kind of looks like the window size of the Read Me app was a calculated decision to ensure it would fit on the 512×342 screen used in black-and-white compact Macs.

Thinking about later models, the Performa 630 series used an internal IDE hard drive instead of SCSI, so the custom version of Apple HD SC Setup was no longer used. I wonder if the Performa 57x series had this partition? You’d think they would have had the exact same software bundle as the tray-loading 550 models. If any readers have a Performa 57x machine, I’d greatly appreciate it if you could check!

How did this functionality actually work under the hood? I haven’t gone too deep into the code (maybe it can be a future post), but I have pieced together a few clues. The “msjy” magic number I talked about earlier definitely plays a part in everything. The special Performa version of Apple HD SC Setup also includes a custom version of Apple’s hard disk driver. This driver contains several references to msjy, so I’m pretty sure that’s what it uses to identify the recovery partition.

I also discovered that the 7.1P4 and 7.1P5 Utilities floppy disks, which were bundled with various Performas, have slightly older custom versions of Apple HD SC Setup: 7.2.1P and 7.2.2P respectively. They also create the recovery partition. The interesting thing about these versions is that it appears Apple accidentally forgot to strip out the debug function names, in both the utility itself and the bundled hard disk driver. They didn’t make this mistake in the original non-Performa 7.2.2 version, and they also didn’t make the mistake in the newer 7.2.2P6 version. Anyway, this is kind of cool, because it tells me the names of functions that look for “msjy” at an offset of 0x9C. Function names in that same area of the driver code include: recvrybootable, confirmminsystem, flushrecoveryflag, recoveryvolexists, and setrecoveryflags. So Apple definitely at least sort of released some of the recovery functionality to the public prior to 7.1P6, despite what their own version history says. And the disk driver is definitely involved in it.

Newer versions of Apple’s disk driver no longer contain the magic number, so at some point they must have abandoned this functionality. In my opinion, it’s a real shame that they ditched it — this could have been very useful going forward on all Macs. They could have even expanded on it and automated more of the recovery process. Sure, it used some of your hard drive space, but it could have been a good trade-off for better reliability.

That’s more than enough technical stuff for one post. I am sharing a download link where you can try this functionality out for yourself if you want. After all, the whole reason I did this was for software preservation purposes, so it makes sense to share it with the world. This is a small piece of Apple software history that, to my knowledge, has not been preserved until now. I uploaded a drive image to the Macintosh Garden. Don’t worry, I didn’t include any of the original owner’s personal data. I started fresh with a blank hard drive image, restored it using the 7.1P6 Performa CD, and then only copied over the restore partition from the dumped hard drive. So this is a factory-fresh Performa 550 7.1P6 install with the recovery partition also present and populated.

The MAME command that I use to boot from this disk image is:

mame maclc550 -scsi:0 harddisk -harddisk1 Performa550.hda -window -nomaximize -ramsize 32M

Of course, you can also test it out on a real machine by copying the hard drive image to a ZuluSCSI or BlueSCSI and naming it something like HD00.hda.

Winding down this super long post now, the main lessons I learned from this research project are:

1. If you get your hands on a vintage computer, strongly consider backing the hard drive up before erasing it. I know it might contain someone’s personal files, so be mindful of that, and of course respect their privacy. But there might still be something hiding in the background that has been lost to time. You never know — it happened here!
2. The fact that many hard drives go bad as they age might actually be a good thing for software preservation. If a vintage computer’s hard drive has a stuck head that can easily be bypassed, someone might sell it as non-working with data intact, rather than erasing it and selling it as “fully tested and wiped”.
3. There are some really awesome people out there in the world!

Special thanks to Pierre for discovering that this functionality even existed in the first place, and getting the word out so we could eventually preserve it. I also have to thank David Pogue and Joseph Schorr for writing about it in their book many decades ago. And of course, huge thanks to the amazing person from Reddit, who asked not to be credited, who gave me the opportunity to borrow and repair the drive that ended up containing the lost partition. You’re seriously the best!

I’m going to repeat this again in case anybody has scrolled all the way to the end. There are still missing pieces of knowledge about how exactly this recovery partition would have been originally created. If you happen to have a Performa 550 with its original hard drive and wouldn’t mind checking for the partition and/or a special version of Apple Backup, please let me know! I would be happy to walk anybody through the process of dumping the drive contents. I’ll send you something if you don’t have the equipment needed to dump a hard drive. Even if the machine has been upgraded to System 7.5 or Mac OS 7.6, it’s still fine — everything could very well still be there, lurking in the background.