21 Jul
2015
21 Jul
'15
11:48 p.m.
I changed the subject line since unless you recognise 43201 others might not make the
connection :-)
On 22 Jul 2015, at 4:18 pm, Eric Smith <spacewar at
gmail.com> wrote:
now, I have just wired up the 43201 on a breadboard in microcode ROM
dump mode, and captured the ROM contents using a logic analyzer.
Photos:
https://www.flickr.com/photos/22368471 at N04/sets/72157653865063443
As someone who has held an interest in the iAPX 432 since it was released, this is an
exciting development, thank you for sharing your intentions and progress.
The 43201 has 4K words of 16 bits of vertical
microcode ROM, however
the top-level control is not done by the microcode ROM, but rather by
a bunch of PLAs and hardwired logic. Many of the simpler 432
instructions are executed without use of the microcode ROM at all.
Do you know if this was where the so-called ?SiliconOS? was stored? was it simply mixed in
with the regular instruction set? For others the SiliconOS provided quite high-level
constructs like resource-scheduling (multi-tasking) and other operating system like
functions, hence the name.
There is not known to be any surviving coherent
release of iAPX 432
software, so I'm developing my own software from scratch.
I guess the other challenge with original iAPX 432 software, if I have this right, is how
dependent it was on the iRMX-86 environment which was used to bootstrap iMAX? so
effectively two operating systems needed to coexist with the supporting hardware, that is
a lot of moving parts and presumably particular software pieces (with dependencies) that
would need to be pulled together.
On your website you mention you have some VAX VMS software that supported the iAPX 432?
does this include any form of cross-compiler? have you tried to resurrect any of it?
It is a
large task, because the iAPX 432 architecture is completely
object-oriented (implemented by the microcode and hardware), and there
have to be several dozen properly formed system objects in memory just
to execute the simplest program.
This is an interesting point of distinction between classes of machines. The Burroughs
B5000 and B6000 families had a similar requirement in that they needed to be a formed
execution environment, with the operating system to function; so dependent were they on
having an OS which could respond to residency interrupts etc. Other system classes by
comparison could be switched on, loaded with stand-alone object-code and do something
useful (obvious examples being the PDP-8 and PDP-11).
By studying the bus
activity leading up to the halt, I hope to be able to determine what
problem with the memory image led to the halt.
May your logical analyser capture all the needed events and your logic probe strike
unerringly.