Re: IIgs memory card

[spec@vax2.concordia.ca (Mitchell Spector)]

In article buggie@ben06.unm.edu (stephen e buggie) writes...

>The chips for the IIgs RAM board are the standard 16-pin DIP rams that say
>"256-xx" on the RAM.

    Well more specifically, 256Kx1 DRAM chips. They must be of the
variety that employs CAS before RAS for the refresh order (I can't
think of a way to indentify which do, only which do not by company
names, batch and date codes).

>The "-xx" number represents the chip speed, and the
>speed must be consistent within each block of 8 chips.

    I'm not so sure that is necessary. Long ago, I used to have a
mix of 150, 120 and 100 nanosecond chips mixed between all banks,
yet this possed no problem. The most important thing to keep in
mind is that they should all be at *least* 150 ns (or faster).

>The more common speeds are:   12,   15,  10,  or 8.

   The IIgs only requires -15 rated chips (150 ns), any faster
would be a waste since the memory would be ready before the
machine is. Still, I've seen Apple cards using 120 ns chips
and my ROM 3 board uses 100 ns 1MBx1 (probably because they
were left overs from Macintosh production). It wouldn't hurt
to use 120 ns rated chips though, it's not like there's any
price difference these days.

>Go to a computer dump or a flea market.   Many older IBM clones have these
>chips in large number.

    Yep, 8088, 8086 and 286's are a great source for these
chips. Once you hit 386 class machines, your not so likely
to find DRAM chips except perhaps on old VGA cards and such
(in those cases they're usually 256Kx4 or 1MBx1 chips).

    Expect to pay $1 or so for a PC/XT/AT board filled with
256Kx1 chips. Heh, and to think it cost me $80 Cdn to buy a
set of 8 chips back in early 1988 (this was back during the
chip storage).

Mitchell Spector
spec@vax2.concordia.ca