Re: IIe 80col/64k card question

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

Michael J. Mahon <mjmahon@aol.com> wrote:

> jsnospam@cimmeri.com wrote:
> >     In my IIe reconditioning project, I've come across two different
> > 80col cards.. an earlier and larger card with about 10 chips and a
> > jumper; and a tiny later card of 4 chips.

Those are actually "extended" 80-column cards (with 64KB of RAM). The
plain 80-column card only has 1KB of RAM and only supports 80-column
text mode. The original one is only a little wider than the auxiliary
slot and has about six chips.

> >     Are these two cards functionally identical, and if so, why does
> > the earlier one have a jumper to enable double hi-res?    Is one more
> > desirable in use than the other?
> 
> They are functionally identical (except for the jumper  ;-), reflecting
> the increasing density of DRAMs during the period of manufacture.
> 
> The jumper was deleted because by that time, everyone left it on.  ;-)

The jumper was there because of a design change in the IIe.

The original IIe did not support double hi-res graphics mode. It was
added in revision B.  I've never seen the original revision - it might
have never been released outside North America, and I expect it was
short lived.

(This is not related to the "enhanced IIe" with the 65C02 and revised
firwmare - that was much later.)

The jumper must be off for a revision A IIe, but can be on to enable
double hi-res for revision B (or later).

The later low profile card with four chips was only supplied
preinstalled in a computer, never sold separately, so there was no need
to have a jumper to ensure it was compatible with an older model.

-- 
David Empson
dempson@actrix.gen.nz