Re: Overlay Revisions

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

In article <41k7bh$6gh@freenet.vancouver.bc.ca>,
Robert Lee_Kwen <trebor@freenet.vancouver.bc.ca> wrote:
> Is there any different between the Apple II overlay card that has the 
> chip 344SOO47 - A    Copyright Apple 86 or
> 
> chip 344SOO47 - B    Copyright Apple 87

That chip is the "Mega II", which is basically an Apple IIe
motherboard (minus the processor and RAM) in a single chip.  It is
also used in the IIgs.  My ROM 1 IIgs (originally a ROM 0) has a 1985
version of this chip, with no letter after the "344S0047", but there
is an "A" at the bottom of the legend.

I don't want to pull open my ROM 3 just at the moment, so I can't
compare it.

> is there any notable differences in them besides there age?

I doubt there would be any significant difference.  It is probably
just some minor tweaking.  Apple seems to have gone through several
versions of many ASICs without telling anyone about what differences
there are.

For example, there are at least three "good" versions of the Video
Graphics Controller (344S0046) and the original "bad" one with the
colour fringing problem.


-- 
David Empson
dempson@actrix.gen.nz
Snail mail: P.O. Box 27-103, Wellington, New Zealand