3 May
2021
3 May
'21
2:47 p.m.
-----Original Message-----
From: cctalk <cctalk-bounces at classiccmp.org> On Behalf Of Bjoren Davis via
cctalk
Sent: 03 May 2021 20:45
To: cctalk at classiccmp.org
Subject: Re: Documentation for F11 Chipset?
Hello Paul and Rob,
The next thing I did was to hook up a logic analyzer to the address lines on
the ROM. This told me how far I got with the boot sequence before it
restarted.
I disassembled the ROM and have some portions of it semi-decoded so that
may be helpful. If you like I can send you the text file I have.
Another helpful thing for me was to take the Xhomer emulator
https://xhomer.isani.org/xhomer/ and instrument it to give me a "good"
ROM boot sequence (correlated nicely with device accesses) and compare
that with what I saw with my logic analyzer.
That's how I figured out my ROM was failing to see an interrupt from the EPCI
(I think the ROM was running the EPCI in loopback mode) and so it was
resetting.
I have to say: the POST on the PC3XX is impressively thorough, but the
mechanism for reporting failures is absolutely atrocious (4 LEDs and, if you're
lucky, a cryptic octal error code on the screen).
In my case all the LEDs come on and stay on, so it isn't executing any instructions at
all. I will look at the ROM next.
I do have a functional 350 that I can instrument, so
let me know if I can help.
If you get the opportunity I would be interested to know how the following signals look:
E22 pin 3
CT1 PT 4 (E22 pin 1)
CT1 PHASE L (E46 pin 8)
You can see how it looks for me here:
https://rjarratt.files.wordpress.com/2021/05/bus-timeout-trace.png
Yellow: E22 pin 3
Cyan: CT1 PT 4 (E22 pin 1)
Pink: CT1 PHASE L (E46 pin 8)
Not shown is trigger off E70 pin 15.
--Bjoren
On 5/3/2021 2:29 PM, Paul Koning via cctalk wrote:
answer.
>
> paul
>
>
> On May 3, 2021, at 2:23 PM, Rob Jarratt via cctalk <cctalk at classiccmp.org>
wrote:
>
> Sadly my machine is not at the point where I can attach a console of any
kind.
The CPU is being reset every 13us by a bus error. I am having trouble
working out why though. I have got as far as working out that is the CT2 TIME
OUT signal, but just why that is active isn't entirely clear to me. It would help
to have a working machine to compare it to!
Regards
Rob
That sounds like it's trying to access the boot ROM and not getting an