cnc@hpcilzb.HP.COM (Chris Christensen) (12/08/88)
from another note: > >The Macintosh Plus and SE both only have space for a total of 4 SIMMs >(the Macintosh II has space for 8 SIMMs). So to upgrade your 1Mb system >which uses 4 256K SIMMs to 2Mb, you have to remove two of the 256K SIMMS >and replace them with two 1Mb SIMMs (giving you a total of 2.5Mb). As >for the 120ns chip speed, that speed is fine in an SE (if I am not >mistaken, the Plus and SE only need 150ns but the increased speed of the >MacII requires the 120ns chips). > I have always heard about making a 2.5Mb Mac+ or a 4Mb one. Can you replace one of the SIMMs to get a 1.75Mb machine or three to get a 3.25Mb one? Or is there something magical about replacing an even number of them? It sure would be nice on my pocket book if I could upgrade one SIMM at a time. Chris Christensen
ecs175f037@deneb.ucdavis.edu (Greg DeMichillie) (12/09/88)
In article <870265@hpcilzb.HP.COM> cnc@hpcilzb.HP.COM (Chris Christensen) writes: > >I have always heard about making a 2.5Mb Mac+ or a 4Mb one. >Can you replace one of the SIMMs to get a 1.75Mb machine or three to get a >3.25Mb one? Or is there something magical about replacing an even number of >them? It sure would be nice on my pocket book if I could upgrade one SIMM >at a time. > >Chris Christensen Sorry, but when adding SIMMS to a Mac Plus or SE you must add them in pairs. That means that these are the possible combinations: Bank A Bank B 256K 256K 256K 256K = 1MB 256K 256K 1MB 1MB = 2.5MB 1MB 1MB 1MB 1MB = 4 MB It is technically possible to have this also: empty empty 1MB 1MB = 2MB although that would mean throwing away the .5MB that was already in you Mac. This is how Apple makes the Mac SE 2/40. You can use third party memory expansion kits that piggy-back another pair of 256K SIMMS onto the existing 256K ones. That would give you a total of 2MB but that is not Apple supported or recommended. And you'd have to throw them away to go to 4MB later on anyway. ----- Greg DeMichillie Apple Student Rep - UC Davis lgdemichillie@ucdavis.edu ucbvax!ucdavis!lgdemichillie AppleLink:ST0178 Disclaimer: If you've seen one disclaimer, you've seen them all.
ephraim@think.COM (Ephraim Vishniac) (12/09/88)
In article <870265@hpcilzb.HP.COM> cnc@hpcilzb.HP.COM (Chris Christensen) writes: >I have always heard about making a 2.5Mb Mac+ or a 4Mb one. Can you >replace one of the SIMMs to get a 1.75Mb machine or three to get a >3.25Mb one? Or is there something magical about replacing an even >number of them? Yes, there is. The Plus and SE have a 16-bit bus. SIMMs are 8 bits wide. Similarly, the Mac II's 32-bit bus requires that you install SIMMs in identical groups of four. Ephraim Vishniac ephraim@think.com Thinking Machines Corporation / 245 First Street / Cambridge, MA 02142-1214 On two occasions I have been asked, "Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?"