68kMLA Classic Interface

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IIsi RAM Upgrade
Posted by: CygnusTM on 2021-08-25 11:26:09 I recently picked up a IIsi. It came with 5MB of RAM (4 1MB SIMMs installed), and I am trying to upgrade to 17MB. I picked up 4 4MB SIMMs on eBay (https://www.ebay.com/itm/224577279767), and the IIsi won't see the SIMMs at all. I've tried reseating it and a PRAM reset. How picky is the IIsi about RAM? My research tells me that the SIMMs I bought should work. I haven't seen anything warning against parity, low profile or 3 chip SIMMs. Thanks.
Posted by: shadedream on 2021-08-25 18:00:31 They should be fine as long as they're 100ns or faster and they need to be installed in a matched bank (four identical simms), though I've not seen anything about parity compatibility so unsure if that would be the issue. This page suggests that it shouldn't be: Classic and Desktop Macintosh 68K Ram Guide
Posted by: Fizzbinn on 2021-08-25 19:24:52 Is this an issue with 2 chip 4Mbit SIMMs vs. 8 chip 1Mbit chip SIMMs? From the Macintosh IIsi Developer Note: “The Bank B expansion memory can contain either four 256 KB SIMMs (made from 1-Mbit fast page mode parts), four 1 MB SIMMs, four 4 MB SIMMs, or four 16 MB SIMMs.” Is the “made from 1-Mbit fast page mode parts” comment really only about 256KB SIMMs? All the 30-pin SIMMs I have are 8 or 9 chip, 256KB, 1MB, and 4MB. Anyone using 2 (or 3, supporting parity that the IIsi ignores) chip SIMMs in their IIsi? (or IIci, which has the same memory architecture from my understanding)
Posted by: bibilit on 2021-08-26 00:43:50 The IIsi is a bit picky about ram, had an issue recently, strange issue is that the IIsi is able to cope with 2Mb sticks and not other machines.
Posted by: CygnusTM on 2021-08-26 07:37:09 They should be fine as long as they're 100ns or faster and they need to be installed in a matched bank (four identical simms), though I've not seen anything about parity compatibility so unsure if that would be the issue. This page suggests that it shouldn't be: Classic and Desktop Macintosh 68K Ram Guide Yeah, that was one of the pages I used when I was researching. These are FPM chips with better than 100 ns speed, so I thought they would work. Is this an issue with 2 chip 4Mbit SIMMs vs. 8 chip 1Mbit chip SIMMs? From the Macintosh IIsi Developer Note: “The Bank B expansion memory can contain either four 256 KB SIMMs (made from 1-Mbit fast page mode parts), four 1 MB SIMMs, four 4 MB SIMMs, or four 16 MB SIMMs.” Is the “made from 1-Mbit fast page mode parts” comment really only about 256KB SIMMs? All the 30-pin SIMMs I have are 8 or 9 chip, 256KB, 1MB, and 4MB. Anyone using 2 (or 3, supporting parity that the IIsi ignores) chip SIMMs in their IIsi? (or IIci, which has the same memory architecture from my understanding) I did find one page (https://oldcrap.org/2018/11/25/macintosh-iisi/) that seems to show a IIsi with 3-chip SIMMs.
Posted by: CygnusTM on 2021-08-27 04:41:02 So after examining the SIMMs more closely and searching part numbers on the PCB, I found that these aren't the Samsung parts stated in the listing. They are actually Siemens parts that I can't find much info on. So they are getting returned. I bought another set that specifically says they work in a IIsi, so I should have better luck with those. Thanks for the insights, everyone.
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