Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!elroy.jpl.nasa.gov!lll-winken!iggy.GW.Vitalink.COM!pacbell.com!tandem!netcom!james From: james@netcom.COM (James L. Paul) Newsgroups: comp.sys.mac.hardware Subject: Re: IIsi memory upgrade questions... Message-ID: <1991Apr4.114513.1234@netcom.COM> Date: 4 Apr 91 11:45:13 GMT References: <1991Apr3.234333.4056@parc.xerox.com> Distribution: usa Organization: Netcom Lines: 57 In article <1991Apr3.234333.4056@parc.xerox.com> schneide@parc.xerox.com (Kris A. Schneider) writes: > >Hi folks, > >Another in the long line of memory upgrade notes... > >My si's currently got 2M (1M static + 4*256K SIMMs). Now, my understanding >is that as long as the memory speeds are fast enough (90 or 100ns I think), >I can mix'n match pretty much as I please. So, my question is, if I plan >on purchasing an additional 4M of memory, why wouldn't I just get a single >4M SIMM instead of 4*1M SIMMs? Seems to me I'd end up with an additional >768K of memory onboard instead of collecting dust somewhere. Although I >haven't been pricing, it would also seem that a single 4M SIMM would be >cheaper than 4*1M SIMMs, no? Oh well, someone please set me straight! > >Oh, before I let you go, let me pose the popular follow-up: where have >folks been getting the best price/quality/service on memory upgrades? > >Thanks much! > >-Kris >schneide@arisia.xerox.com The IIsi has 2 banks of ram. One bank is soldered to the main board and is not removable. This bank is 1 megabyte, and is also used to store the video image. Bank 2 (or B) consists of 4 SIMM slots. GOLDEN RULE: ALL SIMMs IN A BANK MUST BE THE SAME DENSITY. You always change memory configurations on a bank level. Because the IIsi only has one bank, this limits flexibility somewhat. You can only change the SIMMs in bank B. Because the bank has 4 slots, you must change memory in groups of 4 SIMMs. Here are the possible combinations: 1 Meg system: Bank A: 1 Meg (soldered) Bank B: Empty 2 Meg system: Bank A: 1 Meg (soldered) Bank B: Four 256K SIMMs 3 Meg system: Bank A: 1 Meg (soldered) Bank B: Four 512K SIMMs 5 Meg system: Bank A: 1 Meg (soldered) Bank B: Four 1M SIMMs 9 Meg system: Bank A: 1 Meg (soldered) Bank B: Four 2M SIMMs 17 Meg system: Bank A: 1 Meg (soldered) Bank B: Four 4M SIMMs Once again, you cannot mix and match densities in a single bank, which you only have one of in the IIsi that can be changed. So, whenever you change your memory configuration, you have to remove ALL the old SIMMs and either put them into another mac, sell them, or put them on dusting duty. BTW, the 2 meg SIMMs are made just like 4 meg SIMMs, but with half the chips, and the 512K SIMMS are made just like the 1 meg SIMMs, but with half the chips. Thanks for the memories... -- James L. Paul Internet: netcom!james@apple.com | AppleLink: D1231 | CompuServe: 72767,3436 UUCP: {apple,amdahl}!netcom!james | GEnie: J.PAUL | Voice: 415 377-1981 Packet: N6SIW@N6EEG.CA.USA.NA | Delphi: JLPaul | Home Fax: 415 377-0381