Re: mystery ROMS

[dempson@actrix.gen.nz (David Empson)]

Nama <forums6000@mac.com> wrote:

> I have some ROMS that came with some Apple II hardware that I recently
> purchased, and were in a box with some original integer ROMS.
> 
> These ROMS/EPROMS have white stickers on the top and are labled as
> follows:
> 
> A2  1.0
> G2  V2.2
> G3  2.0
> G5  2.0
> G7  2.0
> G8  2.0  1331405
> G10  2.0
> 
> Would anyone have an idea what they could be?

What physical size are they, and how many pins on each chip?

In particular, are they the same width as typical TTL logic chips (about
1/4 inch), or as wide as typical EPROMs (about 1/2 inch)?

The former type may be fusable link PROMs (like used on the Disk ][
controller) or PLDs/GALs or similar logic chips.

The latter type may be PROMs or EPROMs.

Can you see (without peeling off the labels) whether they are made of
plastic or ceramic? Ceramic chips are likely to be EPROMs, while plastic
ones are not (plastic can't withstand the heat from a UV lamp when the
EPROM is being erased).

Assuming they are half an inch wide and 24 pins per chip, they could be
a set of alternative ROMs for the Integer/Applesoft ROM card, which
holds six 2Kx8 PROMs (or 2716 EPROMs). They might be custom firmware of
some kind.

The A2/G2 ROM might be alternatives for the F8 ROM position, which
normally holds the monitor firmware and always has the reset vector.

-- 
David Empson
dempson@actrix.gen.nz