🚀 go-pugleaf

In article <16363@cup.portal.com>, Henry_Burdett_Messenger@cup.portal.com writes:
> Re: "The ST can only address 2 banks"
> 
> I have it on good authority that this is not the case. The ST can address 8
[ stuff deleted]
> henry_burdett_messenger@cup.portal.com
> 				- hbm

Well, I have looked at the schematics, and many more knowledgable than I have
also looked, and we all agree that the MMU found in machines prior to the
Mega's would ONLY support 2 banks of RAM.  I tried to do a 256Kbit 2Meg 
upgrade, gave up, and assumed that in general it wasn't possible 
(especially after someone at Atari said it couldn't be done).

After saying this, some HW hackers in Huntsville, AL produced a 4M
board using only 256K ZIP package RAM (ZIPs weren't required, but the
board they started with had them pre-soldered, so what the heck).

It requires registering some of the address lines using the bank select
as the latch and hoping the RAM is fast enough to still get the data
on the bus in time.  _It can be done_, I have seen it run, but I wouldn't
want to try it myself.

I have heard that the new MMU's support 4Mbit DRAMs so that 16Mbytes of
RAM is possible in only two banks.  Is this true?


--
			- brian

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   Brian McClendon bam@rudedog.SGI.COM ...!uunet!sgi!rudedog!bam 415-335-1110
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