16 May
2005
16 May
'05
7:37 p.m.
Upon the date 19:29 16-05-05, Tony Duell said something like:
I know little about the 9845 hardware at present. I wish I had my own 9845
but haven't found an intact one yet.
I stand by my statement :-) Just a little enlightenment sooner is better
than having to travel through darkness longer :-)
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
Based on that description I would bet that whomever stated the 250 CPU was
the same, except for ucode, had intended the comparison to be to the LPU
which is implied above to be equivalent to the "main" processor (vs the I/O
processor which has less responsibility for calculations, logic processing,
program control, etc.).
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 always wanted to compare the two machines (9845 and HP250) once I
discovered some years ago that the 250 CPU was (alleged to be) the same as
the 9845 CPU. You will have a pinout of the 250 CPU in those drawings to
determine if one of the '45 CPUs essentially match.
I think if you find nearly all pins match to the 250 processor on one of
the '45 processors, based on functions extrapolated from interconnecting
circuit board traces between the '45 PPU, LPU, and adjacent circuitry, then
you have your culprit. If not many match, although the 250 CPU was *said*
to be the same except for ucode (implying sameness hardware-wise), HP had
therefore evidently wire bonded the three differently to accommodate
circuit pinout and/or function requirements.
Device seems big enough to have separate die holding ucode bonded to the
substrate next to the CPU die itself under that cover. Substrate could have
different artwork to accommodate different pin location requirements for
different uses (PPU, LPU, 250). If only contact could be made with an HP
chip fab engineer or tech on these parts to understand this for sure.
I feel this may give you something to work with as you reverse engineer
the
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)
Hmm, great (re: 9825 schema)! I will track down that CDROM again and buy
it. I have a link stored somewhere.
Regards, Chris F.
NNNN
Christian Fandt, Electronic/Electrical Historian
Jamestown, NY USA cfandt at netsync.net
Member of Antique Wireless Association
URL: http://www.antiquewireless.org/