hp proprietary uP history (BPC Processor)

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Mon May 3 22:17:13 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...

The 98x0 proxesor also does that -- you can indirect as many times as
you like (and, indeed, tie the processor in a tight-ish microcode loop if
you get an indirect address that tries to indirect through itself). AFAIK
the 98x0 porcessor has a different instruction set to the 2100 series,
but it's similar in concept.

Received on Mon May 03 2004 - 22:17:13 BST

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