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From: U39648@uicvm.uic.edu (From The Mind Of)
Newsgroups: comp.sys.ibm.ps2.hardware
Subject: Re: Looking for information on IBM PS/2 70-B21
Message-ID: <91127.224820U39648@uicvm.uic.edu>
Date: 8 May 91 03:48:20 GMT
References: <1632@msa3b.UUCP>
Organization: University of Illinois at Chicago
Lines: 27

>Does anyone know if the PS/2 Model 70-B21 is a TRUE 486 machine, or is it the
>PS/2 70-A21 with the "special" 486 upgrade card.  I know, what do I mean by
>TRUE.  Was the PS/2 Model 70-B21 built specifically for the 486 chip.

Ok, your answers are yes, it is a true 486 machine, and yes, it's a
70-A21 with an upgrade card.

The PS/2 Model 70-A61/A21 (60M/120M) was designed to use a 32-bit 25MHz
Intel CPU.  It comes with a processor platform containing a 25MHz 386 and
a 64K static RAM cache.  It was designed originally to be able to replace
the CPU platform with (the then unavailable) 25MHz 486.  This was not
an afterthought.

So, a 70-A21 that has a 486 processor platform installed is the exact
same machine as a 70-B21.

When you buy a 486 processor platform from IBM, they actually take back
the original 386 processor platform, leaving no trace of the humble
origins inside the box... but model/serial numbers never lie.

- Darius
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