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From: rb@cci632.UUCP
Newsgroups: net.micro.atari16
Subject: Re: I *need* memory!
Message-ID: <126@cci632.UUCP>
Date: Wed, 25-Jun-86 12:26:15 EDT
Article-I.D.: cci632.126
Posted: Wed Jun 25 12:26:15 1986
Date-Received: Sat, 28-Jun-86 07:32:07 EDT
References: <8606131855.AA04757@ucbvax.Berkeley.EDU>
Reply-To: rb@ccird1.UUCP (Rex Ballard)
Organization: CCI, Rochester Development, Rochester, NY
Lines: 51
Summary: Second hand info.

In article <8606131855.AA04757@ucbvax.Berkeley.EDU> Mike_Wilson@CARLETON.BITNET (Mike Wilson) writes:
>Hi,
>    I'm currently working on a project to port a new version of Smalltalk
>(examplar-based, multiple inheritance, multiple PROCESSOR, for those who
>are interested) to multiple 68000's on the VME bus. Currently we are
>doing our development on Apple Mac "XL"s, but we are investigating the
>use of other machines (because the Lisas are reaching the end of their
>useful lifespan, and support is lousy!).
>
>   The ATARI 1040 (or 520 for that matter) seems like a reasonable choice,
>except for the question of memory. You see, the Smalltalk image alone (ie.
>without *any* code to execute it) is well over 900K long, so unless we can
>expand memory to at least 2Meg, we can't use them.

According to Abacus literature, the ST series is capable of supporting
4 megabytes, using 1 megabit chips.  Caveat here, these must be 1meg by X
not 256x4 or some similar arrangement.  There are 20 address lines plus
two RAS and two CAS lines.  The MMU doesn't know how to handle 4 banks
of 256x16, but it does appearantly know how to handle 1megx16.

There is no question that, using 1meg by X chips, you can get at least
2 meg stuffed in there.  You could simplify things by getting SIP hybrids.

>   So... My question is: What is the current (read: "Right Now!") limit on
>the amount of expansion memory which is supported by the ATARI?

If you are willing to rebuild the ram banks completely (modest price, some
labor), you can safely get 2 meg for sure.  Getting 4 meg depends on
current requirements of the rams, access times, and general loading/timing
requirements of the 1 meg chips.

>   By the way, an offshoot of this project would probably be a working
>Smalltalk for all ATARIs (Once it works, we could always prune it down to
>fit).

Looking forward to it.

ATARI:  Have you started putting the holes for the SIP rams onto the
board yet?  I realize that actually putting SIPs into the holes would
be too expensive, but it would make atari ram expansion < $70/megX16, and
MUCH easier.

I assume you've calculated the trade-offs between SIP hybrids and
"building your own" RAM banks,  just out of curiosity, how much of
a difference was there (effect on retail price)?  The cheapest ram
boards I've seen were $100/megabyte, most of the hybrids seem to be
priced around $50/megabyte.

Right now, the main weakness of the ST is the difficulty of adding
RAM.  The DMA port could be used for "Paging", but there is no support
for such paging.