Mac SE/30 System 6 Boot with 64MB RAM

My Mac SE/30 Part V: New ROM, New RAM

In Part IV of this series I laid out some of my plans for upgrading the vintage Macintosh SE/30 I’ve been restoring.

I’d ordered a new GGLABS MACSIMM ROM replacement, to raise the system’s max RAM from 8MB to potentially 128MB. I’d also ordered 64MB of RAM, because as far as I knew only half the slots in my machine were functional, and I didn’t want to waste the money until I’d tested it out.

Installing the MACSIMM

Installing the MACSIMM is as easy as swapping RAM: gently unlock the clips that hold the original ROM SIMM in place to pop it out, then pop in the replacement. Here’s the original ROM SIMM:

Here’s the new MACSIMM:

And here’s it is installed in the SE/30’s motherboard:

The next order of business was to verify that the new SIMM worked. So I put everything back together and tried booting up the machine.

It didn’t work.

Instead of a pleasant chime and a Happy Mac, the machine made an awful sound and the display was staticky, snowy mess, commonly referred to as a “simasimac”. In my complete panic I didn’t think to take photos, but here’s some examples. This was the first time I’d started the machine since taking it apart and cleaning it, so it while it could have been a problem the MACSIMM, I couldn’t be sure.

I took everything back apart, reinstalled the original ROM, put it all back together, and was ecstatic that the machine came right back to life. So it was a problem with the MACSIMM, but what? I redid the whole process, and again, simasimac.

After some more research, I discovered in the installation guide for the Mac ROM-inator II (the competitor ROM that I didn’t buy) that there’s an extra hiccup when replacing the ROM on a SE/30. While the SIMMs are electrically compatible across a variety of classic mac models, the SE/30’s ROM board just happens to be physically thicker than normal. So the thinner replacement board doesn’t always make good electrical contact with the slot on the motherboard.

The solution, it turns out, is to ensure good contact by applying pressure to the back of the SIMM (the side without the chips). Since the SIMM is on the edge of the motherboard it’s still accessible even when installed, so I reached in, pressed as specified, then powered up.

It worked! Rather than the standard compact mac monotone startup sound, I was greeted by the II-era chime of my childhood.

Now, obviously leaving the case off and holding the ROM SIMM in place isn’t a long term solution, so time to find some other way to make sure it stays in place. Some users have 3D-printed special brackets to hold the SIMM, but I went with the simpler rubber-band approach:

It looks silly, but having rubber bands pull the SIMM in place is a common fix for this problem, and it works perfectly.

Upgrading the RAM

With the new ROM installed and tested, the next step was to upgrade the RAM. As I said before, I’d been lucky enough to find a good deal on four 16MB sticks, allowing me to bump this machine from its current 4MB to 64MB of RAM. Now in theory, if all of the RAM slots are actually working on this machine, I should be able to put in all the RAM I have and end up with 68MB.

Since older machines (especially the SE/30) can be picky about the order that RAM is installed, I decided my first test would be to install all 68MB of RAM with the new larger sticks in the known good slots and the old smaller sticks in the potentially bad slots.

First I popped out the old 4MB of RAM:

Here’s the new 16MB RAM SIMMs:

And together, here’s all 68MB installed:

Unfortunately it didn’t work. The machine booted to a Sad Mac image with an error code, complaining about the RAM. I tried different combinations of SIMMs, taking some out, putting them in different orders, but it didn’t help.

In the end, it seems the seller was right, there’s something wrong with four of the RAM slots. Rather than attempt a potentially tedious debugging and repair process right away, and glad that I hadn’t wasted the money on a full 128MB of RAM, I settled on just the straight 64MB:

As expected, with the broken slots left unpopulated, the machine booted straight away, confirming my upgrade to 64MB was a success:

As you can see, even though System 6 can only use 8MB of RAM, it still recognizes that there’s 64MB installed in the machine. It just makes it unavailable to running applications by claiming that the system is already using it.

Next Steps

With the new ROM, I’ve made the first of two planned upgrades to this machine. The only other upgrade I plan to make is to replace the dead hard drive with the SCSI2SD. Other than that, it is still my intent to restore everything else (case, CRT, floppy, etc.) to original specs, with the goal to make this machine look and operate like a brand new SE/30 from 1989.

Well, okay, except for this:

I mean, it’s just the power cable right? Who says I can’t have a green power cable?

Stay tuned for Part VI, where I replace the hard drive with the SCSI2SD.

/jon

Want to read from the beginning? Start at Part I.

Mac SE/30 RAM Slots

My Mac SE/30 Part IV: Upgrade Plans

In Part III of this series I took out (and cleaned) the motherboard and disk drives of my Macintosh SE/30. At that point, I was stuck waiting for the upgrades I’d ordered to arrive. But what upgrades exactly?

As I’ve mentioned before, the SE/30 is one of, if not the, most popular model of compact mac ever made. That’s largely due to its speed and expandability – the SE/30 is essentially a powerful Macintosh IIx crammed into the smaller Macintosh SE case. Both the SE/30 and the IIx use the Motorola 68030 processor running at 16MHz with a 68882 FPU coprocessor.

However, despite the many hardware similarities, the SE/30 has one decided limitation: its ROM is “32-bit dirty”, while the ROM of the IIx is “32-bit clean”. What does that mean? Well, the ROM in a classic mac is essentially a bit of permanent software on a (ROM) chip that’s responsible for booting the machine and interfacing between the system and with the hardware.

I won’t get into the history, but having a “32-bit dirty” ROM means the system is limited to a maximum 8MB of RAM. So the SE/30 can only use 8MB of RAM, while the identically powered IIx can use up to 128MB. This doesn’t matter much if you’re running System 6 (which itself is “32-bit dirty” and can only use 8MB of RAM), but if you’re running System 7, it’s an annoying limitation.

But there’s good news! As it turns out, while the software in the SE/30’s ROM can not be updated, the chip itself is actually on a small removable SIMM board. Same with the IIx. So it didn’t take long for enterprising mac enthusiasts to trying putting IIx ROM boards into their SE/30s, and voila, it actually works! With the swapped ROM the SE/30 can see up to 128 MB of RAM. From what I understand, it was a very popular upgrade, and a big part of why the SE/30 became so popular.

My SE/30’s RAM

With that, let’s return to me and my SE/30. While I want the machine to look cosmetically as original as possible, I do want to upgrade the internals a bit, especially the RAM.

As I mentioned in the last post, my SE/30 has the max factory configuration: 4MB spread across four 1MB RAM sticks. I also mentioned that the original seller claimed that the other four RAM slots weren’t functional. Right off the bat, it seems that I’m already at the limit for this particular machine.

Now, if I could get my hands on a IIx ROM board, I could swap out my four 1MB sticks for four 16MB sticks, bumping the RAM to 64MB. Not the absolute max of 128MB, but still a very worthy upgrade.

However, if it’s hard and expensive to track down vintage macs in good shape, it’s even harder and more expensive to find upgrade parts, especially for popular upgrades and especially for parts taken from other vintage macs. But there’s more good news – we don’t actually have to track down an original IIx ROM board.

Modern ROM Replacements

Enter modern enterprising mac enthusiasts, who have created new replacement ROM boards. There are two options in the market today: the GGLABS MACSIMM and the BMOW Mac ROM-inator II. Both are relatively cheap ROM boards that can be installed in SE/30s, as well as other compatible models. Furthermore, both provide useful “customization” options for how the ROM works.

One useful thing they do is path the ROM to disable the memory test at boot. While the 68030 processor is a beast for its time, running a full memory test on 16, let alone 64 or 128 MB of RAM at boot can take up to a full minute. (For reference, when rebooting my SE/30, as-is with System 6, the machine is back to the desktop almost before the startup chime finishes.)

Another patch adds HD20 support, which is a useful (but older) protocol for hard drives that connect via the external floppy port. While I don’t plan on getting or using an HD20 hard drive, it’s useful to have because my Floppy Emu can emulate such an HD20 hard drive, giving me an easy way to transfer large files to and from the machine via SD card.

Now, it’s here that the two products take different philosophical approaches. The base MACSIMM model stops with just the two patches – no memory test plus HD20 support. There’s also a “deluxe” model which adds a built-in, bootable “recovery” disk, so even if you have no other disks installed, or none of them are booting properly, you can still boot into a working system to troubleshoot your machine.

The Mac ROM-inator II on the other hand, comes in only one model, which includes the recovery disk functionality, but also a lot of other customizations as well. The startup chime, a classic hallmark of vintage macs, has been replaced with their own custom tune. The “Happy Mac” startup icon is replaced with a custom “Pirate Mac”, and the startup menu displays some info like the amount of RAM installed, how to boot the recovery disk, etc. Price-wise, it’s also cheaper than both models of the MACSIMM.

My SE/30’s ROM

I want to upgrade my SE/30’s RAM to at least 64MB and I want the HD20 support. With the Floppy Emu and the SCSI2SD, I don’t think I really need the recovery disk. Also, in keeping with my desire for the machine to look and feel original, I was actually turned off by all of the Mac ROM-inator II’s customizations.

In the end, despite having to pay a higher price, I went with the MACSIMM. It helped a little that the Mac ROM-inator II was out of stock at the time. Also, when I contacted GGLABS to confirm that the MACSIMM did not include similar “stylistic” customizations, he explained that he too preferred the basic setup, though he’d happily reflash his board with whatever alternate ROM image I gave him.

So I ordered the basic MACSIMM module and started looking for more RAM. Thankfully, unlike with the protracted ordeal I had finding RAM for the Power Mac 8600/200, I found a seller with 16MB sticks of compatible RAM quite quickly, and at a price within my remaining budget. Still, I limited myself to only ordering four sticks – I reasoned that without any guarantees that all eight slots worked, I didn’t want to waste any money up front. Plus, other than it being really cool, I still wasn’t even sure I’d find a way to use 64MB at once, let alone 128MB.

Alright, now that the plan’s in place, stay tuned for Part V, where I start actually upgrading my machine.

/jon

Want to read from the beginning? Start at Part I.