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From: davidb@brac.inmos.co.uk (David Boreham)
Newsgroups: comp.arch
Subject: Re: A Fast Memory Architecture
Message-ID: <14372@ganymede.inmos.co.uk>
Date: 13 Feb 91 23:45:38 GMT
References: <2012@cluster.cs.su.oz.au> <1991Feb10.013525.1317@zoo.toronto.edu> <11878@pt.cs.cmu.edu> <3187@crdos1.crd.ge.COM>
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In article <3187@crdos1.crd.ge.COM> davidsen@crdos1.crd.ge.com (bill davidsen) writes:
>In article <11878@pt.cs.cmu.edu> agn@unh.cs.cmu.edu (Andreas Nowatzyk) writes:
>
>| Second, by 1 organizations become too cumbersome: consider a 64bit SIMM
>| with 16 Mbit chips: "Sorry, but 128 Mbytes IS our smallest SIMM" :-)
>
>  What's your point? 

Memory factories are only making 16Mbit chips (this is in 1994, say).
Computer wants 64-bit wide memory. You want this on a SIMM and you
try making such a thing with by1 memory devices. 64 times 2Mbyte
is 128Mbyte. User actually wanted 16Mbyte or something less than 128Mbyte.
Can't build such a thing without memory chips wider than 1 bit.
Therfore need wide memory chips. That's the point.

As an example---PC VGA graphics boards need 512K of memory organised
by 32-bits. On the original boards this took 16 off 64K by 4 chips.
Now nobody wants to manufacture 256K DRAMs so they make 64K by 16
(1Mbit) chips instead and the VGA boards can use two chips.
Without the by-16 chips you would either have to carry on using
obsolete and expensive 256K devices or waste money by providing
more memory than is reqired.

>
>  If there's a market for something smaller vedors will sell SIMMs with
>1mbit, or 256k, or even 64k if there's a demand. I guess I can't
>imagine a machine with a 64 bit path which couldn't use a 128MB part.

!

>
>  Cost is certainly not going to be a big deal, like any other part the
>price will come down until it is related to actual cost. And honestly I
>don't see production cost being large for any chip of any complexity, at
>least in comparison to the development cost. Look at the prices of
>memory five years ago, and today. I would expect $10/MB in 1-2 years,

!! There already if you buy enough of them.

>with 4MB bing the usual unit of expansion.

If you want a unit of expansion of 4Mbyte and 64bit datapaths
then you need 32-bit wide chips at 16Mbit.

Sorry for pre-empting the original poster.
David Boreham, INMOS Limited | mail(uk): davidb@inmos.co.uk or ukc!inmos!davidb
Bristol,  England            |     (us): uunet!inmos.com!davidb
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