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Macintosh II Revision A - Memory configuration?

Posted by: egrath on 2022-06-11 12:30:32

Hi,
in a few days i will get a Macintosh II Revision A without memory, so i will need to order new one. I read some articles that with those early revisions it could be problematic to put 8x16 MB or 8x4 MB in it. Can anyone confirm this?

According to https://www.macgurus.com/products/motherboards/mbmacII.php, the maximum in a stock Macintosh II is 68 MB by putting 4x1 MB in Bank A and 4x16 MB in Bank B.

Thanks, Egon

Posted by: Phipli on 2022-06-11 16:15:31

The Mac II needs "PAL" memory for higher density simms. Its a pain to get above 8MB sadly.

These folks have been making some if you contact them : http://www.garrettsworkshop.com/

Or you can make your own. I've made some 4MB SIMMS for my IIx.

Max RAM on the II depends on your ROM revision and if you have an MMU (came with the floppy superdrive upgrade).

Posted by: egrath on 2022-06-12 02:28:35

Thanks for the hint to Garrets Workshop! I just received the device and it's (fortunately/unfortunately/probably) not a stock as the seller advertised:

- It's a revision B board
- Has a 68851 MMU fitted
- Has some interesting ROM chips (3 x ATMEL, 1 x VLSI)
- Has an empty C9 capacitor

As the device seems to have been a workhorse for a technical university in it's previous life (according to inventory stickers on the inside), maybe they have tampered with it already. Time will tell when i finished recapping it. Just ordererd 8 pieces of 1 MB simms, it's probably more than enough for my intended purpose of playing 80s games 🙂

Posted by: Phipli on 2022-06-12 04:30:47

Thanks for the hint to Garrets Workshop! I just received the device and it's (fortunately/unfortunately/probably) not a stock as the seller advertised:

- It's a revision B board
- Has a 68851 MMU fitted
- Has some interesting ROM chips (3 x ATMEL, 1 x VLSI)
- Has an empty C9 capacitor

As the device seems to have been a workhorse for a technical university in it's previous life (according to inventory stickers on the inside), maybe they have tampered with it already. Time will tell when i finished recapping it. Just ordererd 8 pieces of 1 MB simms, it's probably more than enough for my intended purpose of playing 80s games 🙂

GitHub - kr239/Macintosh-IIx-RAM-SIMM: 30-pin SIMM designed for use in the very finicky Macintosh IIx

30-pin SIMM designed for use in the very finicky Macintosh IIx - kr239/Macintosh-IIx-RAM-SIMM

github.com

I wrote the explanation for Kai there if it helps at all, but 1MB SIMMs will work fine. I suggest installing MODE32 and RAM doubler, I ran my IIx like that for ages.

Connectix RAM Doubler 2 - Macintosh Garden

This is a ShrinkWrap 2.1 image of RAM Doubler 2.0 and the 2.0.2 updater. I thought this version deserved a page for itself, as it has certain advantages over the previous versions. The manual above, was sourced from vintagemacworld.com. See also: RAM Charger 2nd DL is a patched version (Disk...

macintoshgarden.org

MODE32 - Macintosh Garden

MODE32 adds 32-bit capabilities to Macintosh models that were capable of supporting a 32-bit architecture, but whose ROM did not. It effectively patches the ROM code in certain models of early 68020 and 68030 Apple Macintosh computers which were misleadingly advertised by Apple to fully support...

macintoshgarden.org

Posted by: unity on 2022-06-12 08:22:30

Its not unusual for Mac Its to ship with a different board than from factory. You may be aware, but both the MMU upgrade and batteries were issues for some. So there was a service campaign for swapping boards that could support the 68851 and thus ass VM support since early boards shipped with 475? with a limited pin socket. Then there was the original battery configuration which was typically less an issue given how long they last, but Apple did create those new battery holders for a reason making servicing easier for the end user.

Personally I prefer the rev A boards since they have no tiny trash can caps that leak and are easy to ID in photos.

Posted by: egrath on 2022-06-14 12:13:24

Thanks for all the answers so far. One more: I intend to run 6.0.8 on the Mac II - i read from various sources that System 6 only supports 24 bit addressing, so essentially all memory above is unusable anyway?

Posted by: Phipli on 2022-06-14 13:40:11

Thanks for all the answers so far. One more: I intend to run 6.0.8 on the Mac II - i read from various sources that System 6 only supports 24 bit addressing, so essentially all memory above is unusable anyway?

Connectix Optima - Macintosh Garden

Connectix's Optima adds 32-bit addressing capability to System 6, allowing more than 8 MB of RAM to be recognized. Sold in separate 32 MB and 128 MB editions. The download on this page includes both Optima/32 v2.0 and Optima/128 v1.0.1. See also MODE32 Maxima

macintoshgarden.org