Re: 65c02 in Apple][

["Bill Garber" <willy46pa@comcast DOT net>]

"Vince Briel" <vbrielnospamme@comcast.net> wrote in message
news:jmRpc.62354$iF6.5503204@attbi_s02...
:
: > > One of the problems is that the CFFA's firmware
: > > utilizes AUX RAM, which does not exist in the
: > > Apple II or II+.
:
: Maybe so, but the fact that it works, even if only
: for a couple of minutes indicates that AUX RAM is
: not the issue. If it utilized AUX RAM it wouldn't
: work period, not have times when it works, others
: when it gives an I/O error.
: >
: > > Timing is also an issue, however, I feel that
: > > timing would also be an issue in the 1 MHz IIe
: > > enhanced machine and it is not.
: >
: > Why would you say that?
:
: The issue is RAM access and the reason it doesn't
: happen on the IIe enhanced is the completely different
: structure for accessing RAM and the fact that they use
: 4164's not 4116's. Custom IC's, reduced overall chip
: count and improved overall system in the IIe is the
: difference.

Ok, I have narrowed the problem down to definitely
timing due to the excess of ICs used in the II+'s
and possibly also due to the many different ram ICs
that are used in them. I had my CFFA in a IIe with
only a GTE 65C02 -2 and no 80 col/64K at all, and it
ran fine. It was an older IIe board from 1982 so it
was unenhanced other than the 65C02. My next attempt
will be to replace the '257s with a faster and more
precise model such as the "HCT" or "F" type. I think
it was the "F" that was recommended. There is also
a jumper recommended I believe to enhance the timing
but I can't remember offhand. I have the doc here for
that somewhere. My II+ has a whole bunch of different
4116's in it, and that is probably not helping. I'll
see if I can find some all the same for the testing.

Bill @ GarberStreet Enterprizez };-)
Web Site - http://garberstreet.netfirms.com
Email - willy46pa @ comcast DOT net
Change DOT to a dot to contact me



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