Xref: utzoo comp.sys.att:8153 unix-pc.general:4211
Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!sharkey!cfctech!rphroy!tkacik
From: tkacik@rphroy.UUCP (Tom Tkacik)
Newsgroups: comp.sys.att,unix-pc.general
Subject: Re: Wait states, why only 4M, 68012, LEDs ; HwNote15
Keywords: HwNote
Message-ID: <19337@rphroy.UUCP>
Date: 29 Nov 89 19:17:31 GMT
References: <613@uncle.UUCP> <214@tapest.UUCP>
Reply-To: tkacik@rphroy.UUCP (Tom Tkacik)
Followup-To: comp.sys.att
Organization: GM Research Labs, Warren, MI
Lines: 38

In article <214@tapest.UUCP> sbw@tapest.UUCP (Steve Wampler) writes:
>In article <613@uncle.UUCP>, jbm@uncle.UUCP (John B. Milton) writes:
>> 	"Does expansion memory run slower than motherboard memory?"

>> When the motherboard layout was re-done, the 74258 was dropped.

>> What all this means is that, if you have an old machine with the piggy-back
>> board and expansion memory, you can get a performance increase by switching
>> to a newer motherboard. Well, I think that horse is dead.

>What if one (me) populated the expansion board with 150ns chips instead
>of the faster (125ns?) chips needed for the motherboard?  I did that because
>of the supposed wait state, but after reading the above, I'm wondering if
>the slower chips *without* a wait state might not be part of my memory
>parity problems.  What is the effect if I don't have a wait state?  (I
>know I could check to see if I have a 74258 or not, but if people say
>it shouldn't matter (other than performance), then I won't bother prying
>open my case!)

It is my understanding that all of the memory in the UnixPC, (OK, newer ones),
need 150ns RAM, with no wait states.
I have not seen a mother board that required 125ns RAM, though is sounds 
like they mat have existed.
All of the memory boards I have seen (both of them) used 150ns RAM with no
problems.  There is no need to use any faster parts.
The expansion board runs with no wait states with 150ns RAM.

I do not think that the UnixPC exits that fell through the cracks,
ie. required one wait state for the expansion memory, but did not have one,
(you would need one of these to have the problem you mention).
But it sounds like there may have been some built that had the extra wait state
but did not need it.


-- 
Tom Tkacik		GM Research Labs,   Warren MI  48090
uunet!edsews!rphroy!megatron!tkacik		Work Ph: (313)986-1442
"Csh must go.  This is non-negotiable!"


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