Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!umich!samsung!brutus.cs.uiuc.edu!wuarchive!swbatl!george
From: george@swbatl.UUCP (6544)
Newsgroups: comp.sys.mac.hardware
Subject: Re: Apple is dumping 120ns SIMMS into SE/30s
Message-ID: <1155@swbatl.UUCP>
Date: 2 Feb 90 15:44:06 GMT
References: <15@hite386.UUCP> <7852@hubcap.clemson.edu> <2827@draken.nada.kth.se>
Reply-To: george@swbatl.UUCP (George Nincehelser 5-6544)
Organization: Southwestern Bell Tele. Co. - Advanced Technology Lab - St. Louis
Lines: 49

In article <2827@draken.nada.kth.se> d88-jwa@nada.kth.se (Jon W{tte) writes:
>In article <7852@hubcap.clemson.edu> jcocon%hazel.cs.clemson.edu@hubcap.clemson.edu writes:
>
>>All 16MHz Macs will run as fast with 120ns chips as with 70ns chips.  The 
>>wait states are hardwired, regardless of memory speed.
>
>>Apple is not dumping.  80ns chips are really a waste in anything less than
>>a IIci, unless you get an accelerator card.
>
>>Apple deserves flaming for somethings, but this isn't one of them.
>
>Nope !
>
>A 16 MHz machine will not run at all if the SIMMS are 120 ns, since
>the data won't be there when the CPU wants it.
>
>"Luckily" for customers with 120 ns SIMMS in their SE/30's (I have
>100 ns, I checked) the classification temds to be conservative and
>allow for temperature changes and aging.
>
>It _is_ bad of apple to put 120 ns SIMMS in a 16 MHz machine. Period.
>
Double Nope!  The first posting is correct.  Only the IIci needs the
fast chips.

According to the Macintosh Family Hardware Reference, the Mac II
(no mention of IIx, IIcx, IIci, or SE/30 in my book) requires 120ns
chips or faster.  Of course, this is a 16MHz machine (approximately).

According to TN 176, the IIci requires 80ns or faster.

According to TN 230...
"Although the 68030 is capable of a burst mode to more efficiently
access contiguous blocks of memory, this feature is not enabled
on the Macintosh SE/30.  Enabling this feature would require
significantly more complex control logic and faster (read ''more
expensive'') RAM."

The "more expensive" is theirs, not mine.  Anyway, I don't see
any mention of speeds in my documentation other than what is noted
above.  Unless someone with more complete resources can show otherwise,
I would have to say that 120ns RAM is fine for everything but the 
IIci (Ignoring the portable here, doesn't it use SRAM?)

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