Xref: utzoo unix-pc.general:1865 comp.sys.att:4918
Path: utzoo!utgpu!watmath!uunet!xanth!nic.MR.NET!umn-d-ub!rutgers!mailrus!tut.cis.ohio-state.edu!osu-cis!n8emr!uncle!jbm
From: jbm@uncle.UUCP (John B. Milton)
Newsgroups: unix-pc.general,comp.sys.att
Subject: Re: 7300 RAM
Message-ID: <442@uncle.UUCP>
Date: 13 Dec 88 06:42:24 GMT
References: <265@arnold.UUCP>
Reply-To: jbm@uncle.UUCP (John B. Milton)
Organization: U.N.C.L.E.
Lines: 42

In article <265@arnold.UUCP> dave@arnold.UUCP (Dave Arnold) writes:
...
>Does anybody know if the expansion memory has any wait states?
I don't know where, but yes, ALL expansion memory has 1.0 wait states.

>Another question:
>
>I have a 512K motherboard with a 1.5meg combo card, and this
>weekend I hope to modify a 512K RAM expansion board with John
>Milton's hardware mod. so I can use it with the combo card.
>Now... what I ultimately want to do, is upgrade the 512K RAM expansion
>board to 2M, and use it with the 1.5meg combo board, giving
>me a total of 4M (.5 + 1.5 + 2.0).  Does anybody know of any
>reason why I can't do this?

Well, the fact that there aren't enough address bits on the expansion connector
to put more than 2M on the expansion bus might be a limiting factor. There
have been many discussions in this group about this.

THERE IS

 #    #   ####           #    #    ##     #   #
 ##   #  #    #          #    #   #  #     # #
 # #  #  #    #          #    #  #    #     #
 #  # #  #    #          # ## #  ######     #
 #   ##  #    #          ##  ##  #    #     #
 #    #   ####           #    #  #    #     #

TO HAVE MORE THAN 2 MEGABYTES OF EXPANSION MEMORY!

The absolute maximum of user, mappable memory in the system is 1024 pages of
4k = 4 meg. Without changing the map rams, all the circuitry concerning them,
all the other stuff that more memory would bump into, and all the kernel vm
stuff, there's NO WAY to go over the 4 meg limit.

The reason I posted HwNote06 is so that people with 1.5M Combo Cards could
fill their expansion memory up to the 2M limit.

John
-- 
John Bly Milton IV, jbm@uncle.UUCP, n8emr!uncle!jbm@osu-cis.cis.ohio-state.edu
(614) h:294-4823, w:764-2933;  Got any good 74LS503 circuits?