Pristine 512k, may have 512ke logic board or ROMs

[risc_management]

I recently received a Macintosh 512k from ebay. This thing is mint, I was shocked at the condition of the case, screen, external 400k drive, keyboard and mouse. This thing is perfectly beige, no yellowing!

Anyway, I've had it a few days and accidentally threw an DS/800k system disk I use with my Plus in the 512k. Lo and behold, she booted... into System 6.0.5... Finder shows the full 800k on the disk.

Apparently the first owner must've had the 512k board swapped with the 512ke board. The Model number is M0001W, which is what the regular 512k should be, so it originally would've had the 400k internal and 64k rom.

How can I ensure that the entire board was swapped, rather than roms changed without pulling the board? It's definitely one of the 512 (k or ke) boards, because the connectors all meet the case openings properly. There is also no indication of mods externally, so anything that was done must've been done by an Apple Service Tech or a real pro.

Is there any way I can pull the Gestalt ID using software? I want to be sure this machine isn't the 512k board with Plus ROMs (although I doubt that is the case since surely they would've increased RAM from 512 to at least 1MB since they were soldering anyway). It has 512k RAM.

I'm just hoping it's a 512ke board, rather than some plus-512 bastardization. From the condition of her, it seems she had owners that would've avoided anything less than a full swap with a 512ke board. Having Plus ROMs in a 512k sort of ruins the idea of having the 512k in the first place...

Thanks!

 

[JDW]

As far as I know, the difference between a Mac 512k and Mac 512ke logic board is nothing more than the two ROM ICs. (I personally own a 512k with original 64k ROMs.) Neither the 512k nor the 512ke had SCSI either.

 

[risc_management]

It's definitely a 512k/512ke board. I am just hoping the ROM chips aren't from a Plus. I will pull the board when I get a Torx driver and find out.

 

[JDW]

It's definitely a 512k/512ke board.

I never disputed that claim. I merely stated in my previous post that those two boards are the same, except for the ROMs. I mentioned that point because in your opening post to this thread you expressed concern over your board possibly being a 512ke board. But I was pointing out that you need not have such concern about the logic board edition since both the 512k and 512ke boards are the same, except for the ROMs.

Now if you have concern, it would be over the ROM revision. And there are only two possibilities here: the old 64k ROMs or the new 128k ROMs. The new ROMs have accelerated graphics routines and allow you to use the HD20 and 800k drives without the HD20 init. But some very ancient software is only compatible with the older 64k ROMs, hence the reason some purists (like myself) prefer the old ROMs.

 

[risc_management]

Apparently this 512K has the Plus 800K upgrade option that Apple offered via its authorized dealers.

The ROM and drive were upgraded in 1987 by an Apple-authorized service technician. I found the paperwork and the manual that accompanied the upgrade.

Now... where to find 64k or 128K fat ROM ICs...

 

[JDW]

Well, if you're 512k is now a 512ke, then you already have the "fat 128k ROMs." And as for finding old 64k ROMs, I can tell you that I've never seen only the ROMs sold on EBAY. You might get someone with a junk machine to extract and sell them to you. That's how I often buy parts. There's no guarantee they will work in such a case, but most often the reason the machine is junk is due to a bad power supply. I doubt the ROMs would be fried. But you'd need to make sure the seller knows what he's doing in order to properly identify the ROMs. He would need to read the numbers on the top of the chips to let you know if they are the original 64k chips or the newer 128k ROMs (which you have now).

I'm sure some people will want to point out that there is more than one revision of the 128k ROMs. And while that's true, it doesn't apply to your Mac 512k. It's only relevant if you have a Mac Plus and an external SCSI hard disk. Since you don't have that, you really needn't worry about the specific revision of the 128k ROMs that you have.

And if you're wondering, yes, you can still use that "new" 800k floppy drive even if you downgrade your ROMs back to 64k. I know this from experience. You don't even need the HD20 init to use the floppy drive either. It will just make more noise and be a bit slower until you use the init. Also, you can't boot off an 800k floppy with the older ROMs using your 800k drive. But you can still book off 400k disks just fine.

Hope this helps.

 

[Quadraman]

A possibility for obtaining ROMs is to try and find a Magic Sac or Spectre 128/GCR for the Atari ST. This was an emulator cartridge that ran System 6 on the Atari's and required Apple ROMS to be plugged into them. They don't go cheap when they do appear on ebay, but they are less than you would pay for an unmolested 128/512 machine.

 

[Charlieman]

Find a pair of ROM images and get somebody to burn them onto EPROMs. I've seen burned 128/512K EPROMs so I know that it is possible. A ROM image for an emulator will not work.

Quadraman: Ataris and Mac ROMs. Alas most Atari enthusiasts wanted the greatest and bestest, and upgraded to 128KB ROMs. Ask for a ROM check before you buy.

 

[JDW]

Interesting idea, Charlieman. I've seen Macintosh Plus and 128 ROMs floating around (people who are into vMac swap them) through the years, but I've never seen a "ROM pair" exchanged. The ROM files you commonly see people swap on the net are a single file that contain all the ROM code. People use some kind of application program that runs on the old Mac and dumps the whole content of both ROM chips into a single file.

So unless you can properly break that ROM apart into code segments for each chip, or unless someone can come up with an INDIVIDUAL IC ROM dumper app, I don't see how it's going to be possible to obtain the necessary ROM codes to burn two EEPROMs. But I admit that if you did have the code and a burner, it would be a far easier and better solution that to find Apple branded ROMs on EBAY!

 

[techfury90]

The 68000 uses a 16 bit bus, so the vMac image could probably be split into odd/even images.