🚀 go-pugleaf

In article <22977@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?

To get parity on a IIci you have to make a special order through your
dealer for a parity machine.  They have to add extra hardware to do the
parity checking.  I am not sure if you need the 9-bit SIMMs for a
parity checked machine, but you do not need it for the normal machines.
The only thing your should be worried about is the speed of the SIMMs.
Make sure that you get the 80ns SIMMs or faster (70ns SIMMs are widely
available) so that you are ready for the IIci.  The SIMMs must also support
burst mode transfers (read only).  This allows the IIci to read in
a whole block of data quickly.  Ask the SIMM sellers to make sure that
their SIMMs are IIci compatible.

The IIfx is a whole different matter.  They use special SIMMs that
have extra pins to allow both read and write burst mode transfers to
occur.  They look like the NTX SIMMs if you have ever seen them.  Since
you can only get them from Apple (currently) don't worry about them.
If you want to move up to a machine like the IIfx, don't buy SIMMs,
wait for System 7.0 or buy Virtual to get more memory.


--------
The above opinions are my own and have no representation of what
my bosses may think.
David Rho
sidlives%mck-csc@eddie.mit.edu
sidlives@athena.mit.edu