It's been a hell of a day! HP 9845/2x i8008/Sage II/2x Grid/TI

[Tony Duell]

> Tony, the HP250 CPU is said to be the same as the 9845* except for 
> different microcode. Reference this website if you can: 
> http://www.hp-eloquence.com/history/history.html

YEs, but _which_ 9845 processor? 

An HP9845 has 2 processors (not counting the graphics accelerator that 
may be in the monitor). One handles I/O (the 'Peripheral Processor 
Unit'), the other runs user programs (the 'Language Processor Unit'). In 
most machines, these are those HP custom hybrid modules with a large 
die-cast heatsink on top, a bit like the processor in the 9825, but with 
different pinouts, etc. 

Soem machnies (and mine is one of them) have the high speed language 
processor option. This replaces the LPU board with its processor with a 
set of 3 boards linked by a little backplane on top. One of the boards 
plugs into the main backplane slot that takes the normal LPU board. The 
other 2 hang over the side of the cardcage. These boards contain (amongst 
otehr things):

Interface PCB : Bus buffers, abritration logic, some processor registers

Data path : ALU (4 off 2901), condition logic, microcode branch PLA, ALU 
decode PLA

Control : Micorocode PROMs, sequnecer (2910), BCD adder and shifter, more 
registers

I am pretty certain than the 2 processors are object-code compatible. But 
I am alos sure that schematics are totally different. I will take a look 
at the ose HP250 diagrams if I get a chance (no, I am not going to spend 
5 hours downloading them here!) to see what that did. But i suspect the 
hardware will again be different.

> 
> I feel this may give you something to work with as you reverse engineer the 
> 9845. You didn't say, and I assume it to be very much the case given the 
> lack of tech manuals for our own 9825 machines, that there was any tech 

FWIW, a reverse-engineered 9825/9831 schematic is on the HPCC schematics 
CD-ROM (along with similar diagrams for the 9100B, 9810, 9830, 9815, some 
late rmachines, and most of the handhelds)

-tony