CST Thor 1 EPROM problem

Nagging hardware related question? Post here!
User avatar
bagpuss22
Bent Pin Expansion Port
Posts: 92
Joined: Thu Sep 29, 2011 10:57 am
Location: East Sussex, United Kingdom

Re: CST Thor 1 EPROM problem

Postby bagpuss22 » Wed Mar 27, 2019 11:51 pm

When it did work, for a short time! I got this boot screen.

Image


User avatar
dilwyn
Mr QL
Posts: 1634
Joined: Wed Dec 01, 2010 10:39 pm

Re: CST Thor 1 EPROM problem

Postby dilwyn » Thu Mar 28, 2019 10:37 am

Could I also ask that the serial number/watermark issues be written up once fully resolved for the Thor information part of my website, please?

Would be good to have the information preserved for the future in case this issue raises its head again for someone else.


lcww1
ROM Dongle
Posts: 17
Joined: Sat Mar 02, 2019 2:34 pm
Location: London, UK

Re: CST Thor 1 EPROM problem

Postby lcww1 » Fri Mar 29, 2019 12:20 am

Russ - great pictures! Nice work on the Thor PCB, and I love the screenshot from the Sinclair monitor - it looks as though your Thor has a few extra ROMs on board!

Dilwyn - I’d be delighted to put something together for the Thor section of your site, which is such a fantastic resource and one which has already been of great help to me.

I’ve heard more from Adrian - he’s been extremely helpful, and he has confirmed that the format of his Thor 1 serial EPROM matches those of mine and Russ - there’s the lingering question of whether there’s a checksum in the serial EPROM, and Adrian is thinking of burning a new serial EPROM for his Thor with a different serial number to see whether that affects booting...

I’ve got a new RTC chip and replacement components for the associated RTC circuitry on order - I’ll report on progress once I’ve been able to do some tests...


User avatar
dilwyn
Mr QL
Posts: 1634
Joined: Wed Dec 01, 2010 10:39 pm

Re: CST Thor 1 EPROM problem

Postby dilwyn » Fri Mar 29, 2019 9:36 am

lcww1 wrote:Dilwyn - I’d be delighted to put something together for the Thor section of your site, which is such a fantastic resource and one which has already been of great help to me.

Thanks Liam.


User avatar
Witchy
ROM Dongle
Posts: 2
Joined: Thu Mar 28, 2019 8:34 pm
Contact:

Re: CST Thor 1 EPROM problem

Postby Witchy » Fri Mar 29, 2019 9:16 pm

Evening all,

I feel like I should've joined the forum years ago since I've been on the mailing list forever, still, better late than never!

Liam, you'll like this:

cstThorNewSerial.jpg


With this new serial number my Thor booted happily into the only demo floppy I have, so the format of the Serial EPROM seems to be:

Code: Select all

0x3FF0: B7  01  EB  01  0B  01  0A  56  08  52  4F  48  54  04
        183 001 235 001 011 001 010 086 008 082 079 072 084 004
        {random number} {-reversed SN-}      R   O   H   T


where the serial is reversed and the first 4 digits are the semi-random number. This does mean that your problem is elsewhere on the Thor unfortunately.

Witchy


--
w: http://binarydinosaurs.co.uk - where RIFA capacitors come to die
f: http://facebook.com/binarydinosaurs, t: @binarydinosaurs
lcww1
ROM Dongle
Posts: 17
Joined: Sat Mar 02, 2019 2:34 pm
Location: London, UK

Re: CST Thor 1 EPROM problem

Postby lcww1 » Sun Mar 31, 2019 1:05 pm

Hello Witchy!
Really glad to see you on this fine forum - and many thanks indeed for your very helpful and informative post- the mystery of the Thor 1 serial/watermark EPROM is solved! Whilst this EPROM rabbit hole hasn't fixed my Thor 1 problem, the investigation has been most rewarding!

I've now replaced a number of the components making up the RTC circuit on my Thor 1 - including the chip sockets for ICs 39 (and IC38, as the sockets of these were corroded), D1 and D2, C5 and C6, and IC39 itself. Alas, none of this has made any difference. The X2 oscillator appears to be ok, and all the PCB tracks in the vicinity check out ok with my multimeter. I've had a quick look on the RTC data bus with a logic analyser, and there's plenty of activity there, but I'll need some time to be able to understand what I'm looking at. Meanwhile, I think I'll try replacing the other easily removable chips, IC36 and IC37, which are involved with the external keyboard, and with the mouse and printer connector respectively. I suppose that it's conceivable that a problem with either of these two chips could prevent the Thor booting.

Along with whatever it is that is causing the boot problem, I think that there is also a problem with the Thor RAM. During testing, I would periodically get RAM errors from Minerva pointing to a RAM expansion fault. Disabling the expansion RAM by grounding pin 9 of IC4 (one of the two PALs on the Thor 1 board), as advised in the Thor TM, has put a stop to such RAM errors.

My thanks again to everyone who has been so generous with their help!


User avatar
Dave
SandySuperQDave
Posts: 2501
Joined: Sat Jan 22, 2011 6:52 am
Location: Austin, TX
Contact:

Re: CST Thor 1 EPROM problem

Postby Dave » Sun Mar 31, 2019 4:28 pm

My Thor 16, which seems to boot but doesn't produce video.

Code: Select all

0x3FFF:  04  :004
0x3FFE:  54  :084 - T
0x3FFD:  48  :072 - H
0x3FFC:  4F  :079 - O
0x3FFB:  52  :082 - R
0x3FFA:  10  :016 - might be the model number?
0x3FF9:  58  :088 - 89/ - year
0x3FF8:  03  :011 - 3/ - batch?
0x3FF7:  01  :001 - 1/ - always 1?
0x3FF6:  2D  :011 - 45 - number in batch?
0x3FF5:  01  :001
0x3FF4:  EB  :235
0x3FF3:  01  :001
0x3FF2:  B7  :183
0x3FF1:  FF  :blank
0x3FF0:  FF  :blank
.
.
.


User avatar
Witchy
ROM Dongle
Posts: 2
Joined: Thu Mar 28, 2019 8:34 pm
Contact:

Re: CST Thor 1 EPROM problem

Postby Witchy » Sun Mar 31, 2019 7:49 pm

Yes! That makes sense about the model number. Mine and Liam's are 8, yours is 16. Excellent :D


--
w: http://binarydinosaurs.co.uk - where RIFA capacitors come to die
f: http://facebook.com/binarydinosaurs, t: @binarydinosaurs

Who is online

Users browsing this forum: No registered users and 3 guests