HP2100a VS HP2100s

From: J. David Bryan <jdbryan_at_acm.org>
Date: Tue Aug 24 11:49:23 2004

On 23 Aug 2004 at 8:10, Jay West wrote:

> As a followup - I just found over the weekend something I wasn't aware
> of. Apparently the 2100A/S isn't "entirely" microprogrammable. [...]
> The other 1/3 of the base instruction set is actually done in hardware
> - mostly.

The 21MX M/E/F computers retain some of this as well. The alter-skip and
shift-rotate instruction groups are implemented pretty much in hardware.
The microcode for these instructions basically just executes ASG and SRG1/2
micro-order "specials," which set up the hardware to implement the
instructions directly.

I don't know if this carried over into the A-Series or not. The A700 ERD
suggests not, but HP didn't provide microcode listings in this publication
to confirm.

                                      -- Dave
Received on Tue Aug 24 2004 - 11:49:23 BST

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