Path: utzoo!attcan!uunet!lll-winken!lll-lcc!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: Re: Ambitious RAM Expansion Hacking
Keywords: 1700 1750 1764 ram expansion remapping
Message-ID: <532@csd4.milw.wisc.edu>
Date: 23 Jan 89 20:53:34 GMT
References: <503@csd4.milw.wisc.edu> <5760@cbmvax.UUCP>
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Organization: UW-Milwaukee Home for Out-of-date 8 bit Hackers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: 48

In article <5760@cbmvax.UUCP> fred@cbmvax.UUCP (Fred Bowen) writes:
>In article <503@csd4.milw.wisc.edu> jgreco@csd4.milw.wisc.edu (Joe Greco) writes:
>	Probably it would be easier just to select the second REU by hanging
>	it off the IO-1 select instead of the IO-2 select.  As long as you
>	have enough power and do not "prime" the DMA's in both to respond to
>	the $FF00 trigger option simultaneously they should work.  Of course,
>	you'd have to provide your own software, since existing software will
>	address the REU at $DF00 only.

That works fine 'till you have several devices demanding I/O pages.  I
decided that the actual work involved in pulling the 74LSxxx and doing
the described modification was less than would be involved in
attempting further decoding within I/O1 and I/O2.

Please note that I haven't done it.... I don't HAVE the second RAM
expander (but I do have plenty of space for it).

Part of the problem is that my software could already use more RAM
than it has access to (used to store massive amounts of data and indexes).

:>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 [...]
>
>	The amount of available expansion RAM aside, in the latest TC128
>	magazine (is it out yet?) I describe a simple patch to the RAMdisk
>	which allows you to "partition" the REU, allocating the lower banks
>	for the RAMdisk and leaving the upper banks available for your own
>	application.  I also provide a simple patch to BASIC-8 to make it
>	compatible with the RAMdisk.

Well I wish I had known that six months ago, when I had to kill the
RAMdisk and use the 1750 for data storage!  :-)  That's exactly what I
wanted back then (now I'm not sure the storage provided by a 1750
would be enough for all the stuff I need to store on a RAMdisk).

All of this aside, is Commodore still producing the 1750?  I have NOT
seen any for sale as of late, and I'm not too anxious to hack a 1764
up to a 1750.

On a similar note.  I finally got my December Transactor.  Has anyone
tried the expand-your-64-to-256K project?  It sounds reasonable.

--
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