68kMLA Classic Interface

This is a version of the 68kMLA forums for viewing on your favorite old mac. Visitors on modern platforms may prefer the main site.

Click here to select a new forum.
Macintosh II SWIM Upgrade ...
Posted by: franklyn on 2026-08-30 06:12:01
I bought a Macintosh II on eBay but haven't received it yet, and I wanted to perform a ROM update and a SWIM upgrade. I have a good SWIM chip from a Macintosh IIcx donor board (344S0061-A). That won't work with the SWIM, though, will it? Because the IIcx SWIM (PLCC) has more pins. If that's the case, is there an adapter available or possible for the SWIM chip? As a ROM replacement, I also have a ROM SIMM for an SE/30.
Posted by: obsolete on 2026-08-30 07:29:49
If that's the case, is there an adapter available or possible for the SWIM chip?
Yes, Kero's Mac Mods sells an adapter: https://en.infinityproducts.co.jp/product-page/super-wh-iwm-swapper-plcc44-to-dip28-swim-adapter
Posted by: franklyn on 2026-08-30 09:29:18
The Plan is I'll desolder the 28-pin PLCC socket, solder in a custom-selfmade adapter with a PLCC44 socket in and hope it works well.

github.com

GitHub - alxlab-zone66x/Apple-SWIM-Chip-Adapters: This project is for a couple of chip adapters to convert the PLCC-28 and PLCC-44 Apple SWIM chips to DIP-28.

This project is for a couple of chip adapters to convert the PLCC-28 and PLCC-44 Apple SWIM chips to DIP-28. - alxlab-zone66x/Apple-SWIM-Chip-Adapters
github.com github.com


What I’m missing is a 2MB floppy drive. The versions from newer computers are inexpensive, but I’m not sure if they can be installed mechanically.

I’m also wondering: if I install the SWIM chip along with the ROM update, will an 800K floppy drive still work until I get a 2MB drive?
Posted by: franklyn on 2026-08-30 09:33:54
I wonder what with pictures was in the Apple original Upgrade Kit ...?

You can't find any pictures on the internet other than of the box. Was there a SWIM version in a special 28-pin chip?
Posted by: franklyn on 2026-08-30 10:10:46
... is the pinout the same for the 28-pin DIP and 28 PLCC?
Posted by: sstaylor on 2026-08-30 10:15:50
The 800k drive will still work. You'll want the auto-inject floppy drive like what came with a Iici, Quadra 700, some SE's, SE/30, Classic, and others.
I installed a couple of upgrade kits in SE's back in the day. Came with the ROM chips, the SWIM, and a floppy drive if I recall correctly (though it's been a minute).
Posted by: franklyn on 2026-08-30 11:45:17
... the SWIM, and a floppy drive if I recall correctly (though it's been a minute).
... was it a 28 pin PLCC SWIM or the 44 pin PLCC SWIM with a 28 pin PLCC Adapter for it?
Posted by: obsolete on 2026-08-30 11:51:32
There is a 28-pin DIP SWIM that came in both the upgrade kits and the SE FDHD/SuperDrive.
Posted by: franklyn on 2026-08-30 12:26:34
I hope that´s work ...
Posted by: franklyn on 2026-08-30 12:28:16
There is a 28-pin DIP SWIM that came in both the upgrade kits and the SE FDHD/SuperDrive.
... the Macintosh II has a IWM 28pin PLCC and not a DIP one.
Posted by: franklyn on 2026-09-02 02:30:16
I bought a Macintosh II on eBay and got really lucky; the machine is in excellent condition, with no leaking batteries. The motherboard has two of them—one still holds a charge of 1.2 volts and the other over 3 volts, which explains why they haven't leaked yet. Aside from some yellowing, the case is in good shape, though there are a few broken struts at the back near the NuBus slots.Finding the missing MC68851 PMMU will be an adventure. I already have a SWIM floppy controller; all I’m missing is a Sony 2MB floppy drive and an EPROM update—neither of which is a problem. I still need to test whether the machine actually works ...?
Posted by: franklyn on 2026-09-02 06:44:30
I replaced the batteries, and everything is working perfectly. I'm currently backing up the Quantum Q250 to my BlueSCSI module...
Posted by: franklyn on 2026-09-02 07:44:52
What newer ROM´s can I use with a original 68020 Macintosh II without a PMMU ...?
Posted by: Froggy814 on 2026-09-02 07:49:28
PMMU
Power Memory Management Unit?
Or
PWM Minebomb Minnanzanee Unified?
Posted by: franklyn on 2026-09-02 07:53:50
MC68851 (Paged Memory Management Unit)
Posted by: Froggy814 on 2026-09-02 08:04:44
That's a silly name. Paged Memory Management Unit.

Thanks!
Posted by: olePigeon on 2026-09-03 14:58:29
What newer ROM´s can I use with a original 68020 Macintosh II without a PMMU ...?
I'd recommend getting a programmable ROM SIMM.
Posted by: zigzagjoe on 2026-09-03 15:36:00
I'd recommend getting a programmable ROM SIMM.
No ROM SIMM in a Mac II 😉 only 4 DIPs. You could write the IIx/IIcx/SE30 ROM for SWIM (FDHD) compatibility, if that's not already done. It looks like 17 address lines are wired, so in theory you could put a 512K IIsi/ci ROM, but that doesn't really add anything useful.
Posted by: franklyn on 2026-09-04 01:53:19
I program a set of FDHD Upgrade Romset and put it in and all works fine even with the original IWM Chip and the 800k Floppy.

The Mac II seems to be very picky about RAM Simm. Currently, Bank A is populated with four 1MB SIMMs and Bank B with four 256KB SIMMs. I have plenty of 1MB and 4MB SIMMs, but none of them work in the Mac II; I always get the "Chimes of Death." However, I know for a fact that these SIMMs are in perfect working order when used in a PC or Atari. I know that the larger ones have to be in Bank A.
Posted by: ESM-NL on 2026-09-04 05:08:13
I have plenty of 1MB and 4MB SIMMs
I read in the Mactracker App for the Macintish II and IIx that 4Mb or larger modules must be PAL SIMMs.
1 >