Path: utzoo!attcan!uunet!lll-winken!oodis01!ncis.llnl.gov!helios.ee.lbl.gov!pasteur!agate!bionet!csd4.milw.wisc.edu!jgreco
From: jgreco@csd4.milw.wisc.edu (Joe Greco)
Newsgroups: comp.sys.cbm
Subject: Ambitious RAM Expansion Hacking
Keywords: 1700 1750 1764 ram expansion remapping
Message-ID: <503@csd4.milw.wisc.edu>
Date: 21 Jan 89 01:12:34 GMT
Sender: news@csd4.milw.wisc.edu
Reply-To: jgreco@csd4.milw.wisc.edu (Joe Greco)
Organization: UW-Milwaukee Home for Out-of-date 8 bit Hackers
Lines: 27

Has anyone managed to run two 1750's on a 64?

Let me back up and describe a scenario:

My system has a 1750 and MSD IEEE interface.  I used to use the 1750
for a RAMdisk, but have since needed to use it for data storage
(swapping).  RAMDOS will not coexist, and there wouldn't be enough
room anyways.  What I want to do is to remap the 1750 someplace else
in the $Dxxx range, and put another 1750 in running with RAMDOS to
provide RAMdisk access.

Breaking down the $D000 block isn't hard, it's just a matter of
pulling thE 74LS239 and adding a second one to decode all 16 256 byte
pages in the region.  Then use one of the select lines to select the
"swapping" 1750.

My question is this:  Has anyone done it?  The REU uses some system
control lines that I have relatively little experience with (DMA, for
instance) and I don't know whether or not they would coexist
peacefully.  I don't see why not, but has anyone done it?

.									JG
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