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| How rare are non-upgraded Mac 128K systems? | |
| Posted by: bigmessowires on 2026-09-26 10:25:57 In the mid-1980s, anybody with a Mac 128K and some money probably upgraded the RAM to 512K, because who wanted 128K? And if you could afford the steep price of the Mac 128K initially, you could probably also afford the price of the RAM upgrade later. So I would expect original condition non-upgraded Mac 128K systems to be pretty rare, notwithstanding occasional eBay listings for $10000 Mac 128K systems - L@@K Steve Jobs! I don't have a Mac 128K, but I do have what I believe is an original Mac 128K logic board, with Apple-branded 4264 DRAM chips. I bought it 10-15 years ago and have never powered it on. Now I'm planning to get it up and running for the trivia game display at Mactoberfest. This board was part of a collection of about five compact Mac logic boards that I bought from somebody at the Silicon Valley Electronics Flea Market for a silly price like $10 for the whole lot.  Other than the obvious lack of RAM and no SCSI support, I can't remember how the 64K ROM Macintosh models differ from 128K ROM models like the Mac Plus. That extra 64K of ROM can't be all SCSI driver. I vaguely recall that some of the icons in alerts and dialog boxes look different on a 64K ROM Mac? Anything else noteworthy? | |
| Posted by: NJRoadfan on 2026-09-26 10:34:31 The 128K ROM adds support for the HFS filesystem, the ability to use 800k floppies or the HD20 on boot, and SCSI. Knowing Apple, they also updated the Toolbox ROMs to the latest revision at the time too. | |
| Posted by: cheesestraws on 2026-09-26 10:43:07 They're kind of middling-rare, IME. I'm not sure why people wouldn't upgrade to 512k when occasion offered; but apparently enough people didn't that they're not stupid rare. They seem to pop up for sale relatively often, sometimes even without hyped-up stress-inducing listings... Apple-branded 4264 DRAM chips Test the memory carefully; those micron/apple 4264s have not aged well. I had to replace every single one in the last 128k board I got working. Other than the obvious lack of RAM and no SCSI support, I can't remember how the 64K ROM Macintosh models differ from 128K ROM models like the Mac Plus. That extra 64K of ROM can't be all SCSI driver. I vaguely recall that some of the icons in alerts and dialog boxes look different on a 64K ROM Mac? Anything else noteworthy? In addition to what @NJRoadfan said, I think more of the toolbox ended up in ROM, and many many bug fixes. | |
| Posted by: finkmac on 2026-09-26 10:44:38 i would say there's no compact macs that are rare. except for like, twiggy macs. | |
| Posted by: bigmessowires on 2026-09-26 11:02:12 Good to know about those 4264 DRAM chips. From a semiconductor physics standpoint, I would be curious to know what makes a DRAM IC go bad over time if it's not powered on and is stored in dry conditions and room temperature. Some kind of oxidation process? Crystallization? Cracking in the package due to humidity changes? Do enough atoms just spontaneously diffuse from one spot to another that it causes failures? My wife just completed her scanning electron microscope training so maybe she can do some de-packaging and failure analysis, haha. | |
Posted by: cheesestraws on 2026-09-26 11:11:50My wife just completed her scanning electron microscope training so maybe she can do some de-packaging and failure analysis, haha. I'm not going to volunteer your wife to take SEM images of old semiconductors for our entertainment... but I am going to strongly encourage her to do so. ;-) That would be really cool and interesting. | |
Posted by: Durosity on 2026-09-26 11:26:59I'm not going to volunteer your wife to take SEM images of old semiconductors for our entertainment... but I am going to strongly encourage her to do so. ;-) That would be really cool and interesting.I am. I volunteer your wife to do the right thing. For science. And for Frodo. | |
Posted by: canuckclassicii on 2026-09-26 19:41:35i would say there's no compact macs that are rare.I would concur… I heard this guy had one once…  | |
| Posted by: Forrest on 2026-09-26 22:13:31 Ugh MT Micron Technology RAM chips, will that company ever amount to anything…seems MU stock is up 588% the past year! | |
Posted by: Juror22 on 2026-09-26 23:12:54I bought it 10-15 years ago and have never powered it on. Now I'm planning to get it up and running for the trivia game display at Mactoberfest.From the photo, it looks like C5, possibly C20 [and C22?] are going bad (check the positive lead on both, it looks like corrosion there). | |
Posted by: David Cook on 2026-09-27 00:15:24non-upgraded Mac 128K systems to be pretty rare Agreed. Your board has the v1 ROMs (doesn't support the later batch of 400K floppy drives) but does have the resistor array bodge on the 6522. So, it is an earlier board that was serviced at some point? Anything else noteworthy? Yes, in the 64K ROM, the tool traps and OS traps are co-mingled. In the 128K ROM, they are separate. The concept of 'unimplemented trap' did not exist in the 64K ROM. And, if you fudge it, it will seem like some traps are implemented when they are really the result of a co-mingled table. For example WaitNextEvent does not exist but will appear to exist on a 64K ROM. Secondly, routines like NewPtr (DisposePtr, NewHandle, etc) did not originally set the result of MemError, surprisingly. If you check for a nil pointer, you're fine. But, if you check the result of MemError you will get noErr even if the pointer is nil. HGetState and HSetState do not exist. MoveHHi might exist if your dev environment has glue for it. See Inside Macintosh Vol IV for all changes. HCreateResFile and HOpenResFile don't exist either. But, since they are resource manager routines, you can get fooled into forgetting they need HFS. The biggest gotcha is when the development environment provides glue routines that expect 128K roms. You will be calling something completely different but the glue crashes because it assumes StripAddress or HGetState exist (etc). - David | |
Posted by: cheesestraws on 2026-09-27 00:44:29Yes, in the 64K ROM, the tool traps and OS traps are co-mingled. In the 128K ROM, they are separate THAT was it. That was the structural thing I was trying to remember and couldn't. Thanks for the reminder! | |
Posted by: impressionist on 2026-09-28 11:59:06Agreed. Your board has the v1 ROMs (doesn't support the later batch of 400K floppy drives) but does have the resistor array bodge on the 6522. So, it is an earlier board that was serviced at some point?At least some toolchains seem to check the ROM version and provide a fallback MoveHHi, I was just looking at that this morning. | |
| Posted by: Huguenot on 2026-10-02 08:29:27 For anyone interested, I am about to list one for sale. Check the trading post forum later today. | |
Posted by: Snial on 2026-10-02 11:38:42At least some toolchains seem to check the ROM version and provide a fallback MoveHHi, I was just looking at that this morning.How can MoveHHi not exist in the 64K ROM, when it, to my mind is essential for efficient heap management? | |
Posted by: joevt on 2026-10-02 16:56:17How can MoveHHi not exist in the 64K ROM, when it, to my mind is essential for efficient heap management?Go to the Apple Documentation Archive https://developer.apple.com/library/archive/navigation/#section=Platforms&topic=macOS Sort by date. Search for MoveHHi There's a tech note: https://developer.apple.com/library/archive/technotes/me/me_03.html There's also these ones which are less relevant but interesting (historically): https://developer.apple.com/library/archive/technotes/me/me_01.html https://developer.apple.com/library/archive/technotes/me/me_02.html https://developer.apple.com/library/archive/technotes/me/me_05.html https://developer.apple.com/library/archive/technotes/me/me_06.html https://developer.apple.com/library/archive/technotes/me/me_08.html The missing me_04 can be found elsewhere. It says: NOTE: This Technical Note has been retired. Please see the Technical Notes page for current documentation. me_07 is also retired: NOTE: This Technical Note has been retired. Please see the Technical Notes page for current documentation. | |
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