CST Thor 1 EPROM problem

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lcww1
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Re: CST Thor 1 EPROM problem

Postby lcww1 » Tue Mar 26, 2019 8:03 am

Hi Derek - thanks a lot for trying! Your experience and mine does suggest to me that perhaps there was not that much data on the Thor 1 serial number/watermark EPROM..... In terms of interfacing the Thor ROM board directly to a QL via the ROM connector, I’ll look at the Thor/QL schematics in the Thor technical manual...

And Dave - thanks to you for your helpful suggestions - I can’t send PMs as yet, but I’ve seen some of Urs König‘s QL videos on YouTube, and I think he has a website, so I can probably find a way of contacting him. In terms of the Thor 1 ROMs on Dilwyn’s site, these all appear to be various versions of the Thor 1 QDOS extensions, and I’ve not found anything there relating to the serial no/watermark EPROM. I’ve been scouring the Thor 1 technical manual that you linked to, and it certainly describes a process whereby the Thor OS reads the serial number/watermark, but there’s no real detail on the contents of the serial number/watermark EPROM, though the data format of the serial number is described.

So, I’m beginning to think that all the important Thor 1 specific OS extensions are in the Thor 4.xx EPROM, and that the second 8k EPROM is just a machine specific serial number container and doesn’t harbour much else. Without an example of a working Thor 1 serial number EPROM, I think it will be difficult to recreate such a thing, but I wonder about disassembling the Thor 4.00 EPROM code to see whether the code could be modified to bypass or spoof the serial number read/test ... ??? Alternatively, a dissassembly might allow a sufficient understanding of the serial EPROM that it could be recreated...


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vanpeebles
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Re: CST Thor 1 EPROM problem

Postby vanpeebles » Tue Mar 26, 2019 8:45 am

Your PM's should be enabled by now, just takes a couple of posts :)


lcww1
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Re: CST Thor 1 EPROM problem

Postby lcww1 » Wed Mar 27, 2019 12:09 am

Thank you vanpeebles!

I’ve sent an email to Urs König, and also to Adrian Graham via his binary dinosaurs website, as he seems to have a working Thor 1 - http://www.binarydinosaurs.co.uk/Museum/cst/index.php. Lastly, I’ve PMd forum member bagpuss22 whose thread here - https://qlforum.co.uk/viewtopic.php?f=20&t=1807&hilit=CST+Thor+1 - mentions that he had successfully dumped both the Thor 1 EPROMs from his machine.
Meanwhile, I’ll make a start on the Thor 1 Argos/OS extension ROM disassembly .....


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bagpuss22
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Re: CST Thor 1 EPROM problem

Postby bagpuss22 » Wed Mar 27, 2019 12:07 pm

Hi there,

I will dig the ROM images out later..

When back-powering the CST QL mainboard, are you just applying just the +5v ?

I have to get back into the swing of this lol..

I need to test my board away from the CST expansion, after applying 9v! DOH!

Russ


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Dave
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Re: CST Thor 1 EPROM problem

Postby Dave » Wed Mar 27, 2019 4:39 pm

I feel your pain. I lost my original owned since the 80s Sandy SuperQBoard v3 (literally, the first one made) this way. I will rebuild her, but still... I feel your pain.


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bagpuss22
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Re: CST Thor 1 EPROM problem

Postby bagpuss22 » Wed Mar 27, 2019 4:54 pm

Looking at the 2 rom images, mine on the left and your on the right, the layouts are similar and do
contain the key number written on the label.

Will need to check mine as yours seems to be 8K and mine 16K.......

Image


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Dave
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Re: CST Thor 1 EPROM problem

Postby Dave » Wed Mar 27, 2019 5:23 pm

At this point, a little write-up on how to create a working serial EPROM with the machine's original valid serial number would be a useful addition to the knowledgebase.


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NormanDunbar
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Re: CST Thor 1 EPROM problem

Postby NormanDunbar » Wed Mar 27, 2019 6:25 pm

Dave wrote:At this point, a little write-up on how to create a working serial EPROM with the machine's original valid serial number would be a useful addition to the knowledgebase.


And, indeed, the wiki too as well also. (https://qlwiki.qlforum.co.uk) <----- That was a subtle hint! :D :D :D


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lcww1
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Re: CST Thor 1 EPROM problem

Postby lcww1 » Wed Mar 27, 2019 11:20 pm

Wow! Thanks so much Russ! This is fantastic progress! I'm most grateful for your help with this serial EPROM.

When I was back-powering the CST QL mainboard, I did indeed just apply 5v from the Thor board expansion connector to the QL expansion connector - before dismantling the Thor, I'd just happened to notice in the Technical Manual section dealing with external microdrives that the 9v and 5v lines on the CST QL were linked together!

So, thanks to your investigations above, it does indeed look as though the Thor 1 watermark/serial number EPROM is pretty sparse!
As you note, the serial numbers of our respective Thor 1s are present in both EPROM dumps as 4 bytes, along with some other data.

Now, looking in the Thor 1 technical manual, there is the following description of a Trap to read the Thor 1 serial number:
FS.WATER.png
Thor FS.WATER Trap


So, referring to this entry of the TM, and since "ROHT" as ascii hex is 52 4f 48 54, we can see that the data in last two columns of data shown in the hex dump in Russ's post above correspond to the D1=0 machine name field; D1=1, and the first two columns contain the D1=1 serial number/identifier field, which consist of the 4 byte serial number, and another 4 bytes apparently consisting of a 32bit semi-random number!

Both Urs König, and Adrian Graham have got back to me about their Thor 1 serial EPROMs, so if their serial ROMs also appear similar to those shown in Russ' post above, then I think we can be pretty sure of the serial EPROM format.

With this information in hand, I think that I can now exclude corruption of the serial EPROM as the cause of the failure to boot of my Thor 1. I've burnt a new Thor 4.22 OS EPROM, and I have the same boot problem with that, so I think neither of the Thor EPROMs are the problem.

Looking again at where the Thor boot process hangs, and remembering that section 4.05 of the TM mentions that the RTC is read during the boot sequence, it occurs to me that my problem may relate to the RTC. The RTC chip is right next to where the Ni Cad battery was, and there was some corrosion on the legs of the Hitachi HD146818 RTC chip (IC39). The TM states that when "the system has been powered-down for some length of time, then the message 'the clock has been reset' will be displayed on the screen" - there's a screenshot of this on the Binary Dinosaur website here - http://www.binarydinosaurs.co.uk/scripts/picshow.php?image=/Museum/cst/DSCF5655.JPG&back=/Museum/cst/index.php - I'm not seeing this message at all, so I suspect that the Thor OS is trying to read the RTC, failing, and getting stuck. I should probably replace the Hitachi HD146818 RTC chip, and possibly some of the other components in the corner of the PCV where the battery lived, such as Q2, and X2, and possibly D1 and D2.

Lastly, I've had a quick go at disassembling the Thor 4.00 OS ROM - I'll attach the disassembly here in case anyone's interested - it may shed some light on matters in due course...

cst_thor_400_eprom.bin.txt.zip
Thor OS 4.00 disassembly
(114.55 KiB) Downloaded 24 times


Once again - thanks to everyone who has helped with this effort! I really appreciate the spirit of this forum :)
Finally, I'll be very happy to contribute to the QL wiki....
Last edited by lcww1 on Wed Mar 27, 2019 11:56 pm, edited 2 times in total.


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bagpuss22
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Re: CST Thor 1 EPROM problem

Postby bagpuss22 » Wed Mar 27, 2019 11:50 pm

I had to repair the same area! Replaced most of it.

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After:
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