68kMLA Classic Interface
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| How do I know if my macintosh II has a PMMU or HMMU? | |
| Posted by: NegativeLatency on 2021-01-22 09:00:33 Background: I have a macintosh II that I'd like to get A/UX running on (it's partially complete, needs a hard drive and a video card) I'm not sure if the main board has a PMMU or HMMU (I suspect it has an HMMU and was wondering if anyone knew for sure) Here's a shot of the CPU, FPU and the MMU which doesn't appear to be the MC68851 chip.   Follow up question, could I replace the existing MMU with a PMMU like the one on this ebay listing: https://www.ebay.com/p/556755362 | |
Posted by: NegativeLatency on 2021-01-22 09:45:37 I think I found the answer in "Macintosh II Repair and Upgrade Secrets", my board has the HMMU Seems like that part from ebay will work? | |
| Posted by: 360alaska on 2021-01-22 10:06:23 Yep, PMMU usually has a gold top. | |
| Posted by: NegativeLatency on 2021-01-22 11:29:54 Also found this on the AppleWiki The 68851 allows a 68020 processor to support virtual memory. The only Macintosh model with a socket to accept a 68851 was the 68020-based Macintosh II. However, the socket was shipped with a lower-cost VLSI VI475custom hardware memory management unit (HMMU) which did not support virtual memory like the more expensive 68851.https://apple.fandom.com/wiki/Motorola_68851 | |
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