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From: rknop@nntp-server.caltech.edu (Robert Andrew Knop)
Newsgroups: comp.sys.cbm
Subject: Re: 1764 memory expansion
Message-ID: <1991Feb9.004346.18305@nntp-server.caltech.edu>
Date: 9 Feb 91 00:43:46 GMT
References: <1429@tau.sm.luth.se> <1991Feb7.224318.1@uwav1.u.washington.edu> <1991Feb8.155348.9033@news.nd.edu>
Organization: California Institute of Technology, Pasadena
Lines: 28

treesh@vangogh.helios.nd.edu writes:

>I have self-expanded my 1700 to a 1750 clone.  This expanded unit works great
>for me for what I use my REU for, but I dont use it with GEOS.  My REU works
>as a "Ram drive with out a device number" as quoted from my software manual.
>There is a driver file on the software that I am running, wich is C-Net 129
>v5.0.  The software runs in C128 mode, mostly in Basic 7.0 for the most
>part, but the REU stuff is in ML.  If I where to get my REU expanded to
>1 or 2 megs of ram, would I be able to access it via Basic 7.0, or would
>speical driver software be needed?

Yes, it will work, but will you be able to take advantage of the >512K memory
is another question.  My guess would be no, but it depends on how the program
is written.  The means of accessing expanded REU's is a direct logical
extention of the means of accessing the first 512K.  However, there is a
single bit flag in the I/O block, which is set off for a 1700, on for a 1750.
Most programs probably will test this flag, see that it is on, and think that
they have only 512K of expanded RAM, when really they could get at as much as
1.5 Meg more without any need to resort to programming tricks (you simply ask
the computer to load from a higher address in the REU, same exact procedure as
for low addresses in the REU).  Some programs, e.g. GEOS with Configure2.1,
explicitly test your REU, by trying to write/read from each 64K bank, to
figure out how much expanded memory there is.  It would be nice if all
programs operated this way, but... well, that's always how it is with new
hardwrae.

-Rob Knop
rknop@tybalt.caltech.edu