Re: odd cards

[quadrajet1@aol.com (Quadrajet1)]

>I have used 9 chip and 3 chip SIMMs from PC's in Macs from the Plus on,
>with
>no problems.  The Macs just don't use the parity bit. I'd expect the OctoRAM
>card to work the same.
>I think these myths come about when someone puts a bad SIMM in a computer
>and has problems, then figures that type of RAM doesn't work.
>I don't think the computer can tell the difference between the 2 or 3 chip
>and 8 or 9 chip versions. The 3rd/9th chip provides  the parity bit, not
>used by Macs and probably Apple II RAM boards.  4 of the remaining chips
>from the 8 or 9 chip SIMMs are the equivalent of 1 of the chips on the 2
>or 3 chip SIMMs. The computer doesn't know or care that they are packaged in
>one chip instead of 4.
>
>So: bad SIMMs of any kind won't work. If you are having problems, try to
>get another SIMM or set of simms. 1 meg SIMMs only cost $1 or so, now. You can
>find the bad one by the process of elimination.
>-Paul

   I have upgraded many computers over the years, and know for a fact some
Apple's don't like the 2 or 3 chip SIMMs.  I am not saying you can put them in
one particular machine with a certain kind, but as a general rule stay away
from them on old machines.  I have had success with some, and others I have
not.  Here's a old document straight from Apple TIC Archives:

------------------------------------------------------------------------
I'm trying to use the new "quad density" 1MB RAM SIMMs (two chips per SIMM) in
older Macintosh computers.

By trial and error, I discovered that the two-chip SIMMs won't work in the
Macintosh Plus or Macintosh II. I tested some of these SIMMs from a Macintosh
Quadra in a revision A Macintosh II and they cause it to fail the memory test.

In what Macintosh computers will these SIMMs work?

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DISCUSSION 

The two-chip SIMMs are one-megabyte SIMMs that use four megabit components
(four megabits per chip times two chips equals 8 megabits -- eight megabits
divided by eight bits per byte is one megabyte). The four megabit components
are now cheaper than the one megabit components previously used.

The following models do work properly with these two-chip SIMMs:

* Macintosh Classic II
* Macintosh SE/30
* Macintosh LC/LC II
* Macintosh IIsi 
* Macintosh IIcx
* Macintosh IIci 
* Macintosh IIvx/IIvi 
* Macintosh Quadra 700
* Macintosh Quadra 900/950

Article Change History: 
31 March 1994 - Clarified title and chip SIMMs, revised formatting.

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   I don't fully agree with the list, but hey, it's from the horses mouth.

Raymond