Re: apple II roms and eproms

[David Wilson <david@uow.edu.au>]

David Wilson <david@uow.edu.au> writes:
>Apple IIgs
>ROM00/01/03 1 megabit		???	none	28

>The IIgs uses a 28 pin 1 MegaBit (128KB) ROM but the
>equivalent EPROM has 32 pins...

I just double checked the ROM03 schematics, my memory data book
and my ROM03 PCB.

1) The PCB is laid out for 32 pin sockets (but my IIgs
has only got 28 pin sockets soldered to it).

2) There are two versions of 128Kx8 EPROMs. One has /OE on
pin 24 and is not usable in the IIgs. The other has A16 on
pin 24 and /OE is on pin 2. Compatible EPROMs are:

Hitachi HN27C301G
Toshiba TC571001D

So if your ROM03 has 32 pin sockets you can use EPROMs.
-- 
David Wilson  School of IT & CS, Uni of Wollongong, Australia