mkao@cory.Berkeley.EDU (Mike "Butterball" Kao) (03/13/90)
I learned from my digital design professor that the newest Macs (beginning witht he IIci I think) have added a parity bit to each byte, now resulting in 9-bit bytes. I suppose this means that these Macs use 9-bit SIMM's? I want to know because I currently own a Mac II with 4 MB and am considering buying 4 more MB to bring my machine up to the max; however, I am concerned that, should I decide to upgrade to one of these newer Macs, all my SIMM's will be useless. Is this true? -------------------------------------------------------------------------- PLEASE reply via E-MAIL to insure my receipt of any replies. Thank you!!!! FINALLY! A permanent address........................mkao@cory.berkeley.edu ------------------------------Pi Kapp, Gamma------------------------------
marc@Apple.COM (Mark Dawson) (03/13/90)
In article <22978@pasteur.Berkeley.EDU> mkao@cory.Berkeley.EDU.UUCP (Mike "Butterball" Kao) writes: > >I learned from my digital design professor that the newest Macs (beginning >witht he IIci I think) have added a parity bit to each byte, now resulting >in 9-bit bytes. I suppose this means that these Macs use 9-bit SIMM's? > >I want to know because I currently own a Mac II with 4 MB and am considering >buying 4 more MB to bring my machine up to the max; however, I am concerned >that, should I decide to upgrade to one of these newer Macs, all my SIMM's >will be useless. Is this true? NO! There are two types of IIcis--parity and non-parity (I'm not sure if the parity ones are shipping yet). If you put parity SIMMs in the non-parity IIcis, you've only wasted your money getting more expensive SIMMs--you won't get parity, nor will there be any hardware penalty (you will have the $$ penalty). If you put non-parity SIMMs in a PARITY IIci, you'll only have wasted the extra cost of the parity machine--you won't have parity. In the IIci w/parity, ALL of the SIMMs must be parity SIMMs for parity to be enabled. (if you have a parity IIci && don't have parity SIMMs installed, you'll get an alert box everytime you boot telling you that parity has been DISabled--just press "continue" to go on with the boot). In other (shorter) words, non-parity (8bit) SIMMs will work on all IIcis and so will parity (9 bit) SIMMs. Unless you have a burning desire (and extra $$)for parity, I'd suggest you just get fast (80ns fast-page mode SIMMs--though these seem to becomming "regular" speed) SIMMs when you upgrade. Mark -- --------------------------------- Mark Dawson Service Diagnostic Engineering AppleLink: Dawson.M Apple says what it says; I say what I say. We're different ---------------------------------