hp proprietary uP history (BPC Processor)

From: Bill McDermith <bill_mcdermith_at_mcdermith.net>
Date: Mon May 3 13:09:28 2004

One other peculiarity I do remember about the BPC instruction set was that
as it had byte addressing, the byte select was the _most_ significant
bit of a
16-bit address, so that the indirect addresses were only one level -- that
is, you could do indirect addressing through one target word -- this is in
contrast to the 2100 instructions where the most significant bit was used as
an indirection bit indicating a chain of indirect addresses...


Bill McDermith wrote:

> Jay West wrote:
>> A combination of 2100 and 21MX instruction sets? Umm... the 21MX is
>> just a
>> superset of 2100?
> Correct, but if my memory isn't completely gone, it had some
> of the 21mx instructions, some of the additional registers, like
> the amusing but less useful index registers, but not all of the
> 21MX instructions, and some of the ones that were included weren't
> implemented in the same way (or with the same bit pattern? Can't
> remember...) -- It seems to me that you couldn't just use a
> 21MX compiler to target a BPC, for example.
> It's just hard to remember, programmed it every day for a year
> in 1980, then moved on to the displays division in Colorado
> Springs, and never messed with it again...
> Bill McDermith
Received on Mon May 03 2004 - 13:09:28 BST

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