Path: utzoo!mnetor!uunet!lll-winken!lll-tis!oodis01!uplherc!sp7040!obie!wes
From: wes@obie.UUCP (Barnacle Wes)
Newsgroups: comp.sys.atari.st
Subject: Re: Expandability
Message-ID: <215@obie.UUCP>
Date: 3 May 88 04:29:41 GMT
References: <880501040119.855327@HIS-PHOENIX-MULTICS.ARPA>
Organization: Great Salt Lake Yacht Club, north branch
Lines: 19
Summary: 4 megs, and why...

In article <880501040119.855327@HIS-PHOENIX-MULTICS.ARPA>, Friesen@HIS-PHOENIX-MULTICS.ARPA writes:
| I have heard very different stories, I have heard that 4 Megs is a high
| as you can expand a 1040, I have heard that 4.5 Megs is as High as you
| can expand the 1040, and I have heard that 16 Megs is as high as you can
| expand the 1040.
| [...]
| I didn't hear why there was a 4.5 Meg limit.
| 
| Well, which is it?

The addressing limit on the ST without hacking the hardware is 4 meg.
The MMU chip does the majority of the address decoding, and it only
deocodes a1..a21.  If you "fall off" the end of the MMU, it will
(should?) give you a bus error or address error.  This could, of
course, be changed by replacing the MMU chip.
-- 
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