The Sinclair QL Forum

Pr0f wrote: Sat Dec 21, 2024 9:30 pm A 27512 EPROM won't work - as the sockets have VCC wired to where A15 should be. Instead - the masked ROM's that Sinclair used are a pair - one activated by a high chip enable - and the otehr by a low chip enable - and these use A15 on what would be the chip enable to decode the 32K and 16K blocks - the sockets themselves are effectively wired in parallel (this is why you can piggy back the ROM chips) and fit them to just one socket.

It is a shame Sinclair didn't wire the socket like a standard JEDEC Eprom - so that a 64K ROM chip could be used.

Ah yes, the A15 thing. So the way this is wired is ok from normal EPROM pinout for chips that do not have an A15 (27128 and 27256)... so I could therefore use 27128 and 27256 EPROMS with the full 48k ROM on them. Which I'm sure is what Sinclair did for some that were upgraded from dongle to internal.

At first sight, this doesn't look like a production ROM. The locations from $00C0 onwards contain a jump table, pointed to by the various exception vectors, and the targets of the JMPs are in the $C000-$C08C range (i.e. ROM dongle!). This also means that the vectors starting at $00C0 are missing so any applications using these vectors would fail.

Interestingly, there is a gap of about 7.2K in the code containing all zeros (from $5398 to $6FFF) and it uses the last 2K of RAM for a jump table used by TRAPs #0 to #7 (!)

I've tried running it on an emulator; I do see the tweed pattern at the start but after that it crashes, which is of no surprise of course as the upper 16K is missing.

I've noticed the '1.00' (probably in the code of the MT.INF trap). From Pennell's bible I've gathered that FB was version 1.01 so this must probably be pre-FB. It doesn't match up with the upper 16K of the FB ROM.

Thanks Jan.

Such a shame that the missing third will remain missing unless the owner of the dongle ever realises and sees this thread.

Chr$ wrote: Sun Dec 22, 2024 12:05 am Such a shame that the missing third will remain missing unless the owner of the dongle ever realises and sees this thread.

The jump table into the $C000 range suggests that there should be some code there. But how do you get code there if the ROM port is already occupied by the 'missing' 16K at $8000? Maybe there should have been some debugging equipment attached to the expansion port?

QLvsJAGUAR wrote: Wed Apr 26, 2023 5:41 pm I did some investigation, tracking back the seller of this QL on ebay. There was a second auction from the same seller where the
"Sinclair QL EPROM Cartridge Board with an EPROM labelled 13-2-84 8000 0D0C as checksum" was sold. Most likely this would fit to this QL computer with the ZX-83 PCBA. See picture.
Sinclair QL EPROM Cartridge Board with EPROM labelled 13-2-84 8000 0D0C as checksum - this fits to QL computer with ZX-83 PCBA - I-s-l1600.jpg
Key question is who the buyer of this is!?

Another look at this photo reveals that this dongle has room for 2 EPROMs, but the left socket is empty.

Was the empty one perhaps being used for debugging code at $C000?

The order of code is very different from the production ROMs. It looks like the lower ROM area contains SuperBASIC code, then there is the 7.2K gap before $7000, and after that there appears to be QDOS code. This coincides with the 'QDOS' sticker on the EPROM in the dongle.

janbredenbeek wrote: Sun Dec 22, 2024 1:49 pm

QLvsJAGUAR wrote: Wed Apr 26, 2023 5:41 pm I did some investigation, tracking back the seller of this QL on ebay. There was a second auction from the same seller where the
"Sinclair QL EPROM Cartridge Board with an EPROM labelled 13-2-84 8000 0D0C as checksum" was sold. Most likely this would fit to this QL computer with the ZX-83 PCBA. See picture.
Sinclair QL EPROM Cartridge Board with EPROM labelled 13-2-84 8000 0D0C as checksum - this fits to QL computer with ZX-83 PCBA - I-s-l1600.jpg
Key question is who the buyer of this is!?

Another look at this photo reveals that this dongle has room for 2 EPROMs, but the left socket is empty.

Was the empty one perhaps being used for debugging code at $C000?

The order of code is very different from the production ROMs. It looks like the lower ROM area contains SuperBASIC code, then there is the 7.2K gap before $7000, and after that there appears to be QDOS code. This coincides with the 'QDOS' sticker on the EPROM in the dongle.

I believe all of the dongles had space for 2 chips. The one I have certainly does. One of them - I can't remember which side - appears to be for the 16k of code that should have been internal (not populated in my dongle) and the other space was for the regular ROM expansion 16k area (which in my dongle is the syscomp test routine).

Chr$ wrote: Sat Dec 21, 2024 9:17 pm MetroZodiac was kind enough to sell me this ZX83 QL and I've just returned home with it. Credit to him for cleaning it up so well, it's in fabulous condition.

My first post in over 4 months. I was following the forum every now and then using a feed. I have had a hard 2024 in multiple aspects and almost died in a harsh road accident in October. Am recovering.

Great that this QL computer is not lost forever. Congratulations Chr$ for the catch. I was angling for it to, tried to communicate with MetroZodiac, but from a certain point, did no longer get any response from him.

I trust the QL is in good hands now.

Chris, can you tell us the story of the purchase? Did you travel from Germany to England (Wolverhampton?) to meet the seller and collect the machine. Any anecdotes?

What is a shame, is that the buyer of the ROM port dongle is not (yet) known. He may not know that the content of that 27128 EPROM labelled QDOS 8000 13-2-84 is very important in respect to Sinclair QL history & software preservation.

Cheers, Urs

janbredenbeek wrote: Sun Dec 22, 2024 1:49 pm The order of code is very different from the production ROMs. It looks like the lower ROM area contains SuperBASIC code, then there is the 7.2K gap before $7000, and after that there appears to be QDOS code. This coincides with the 'QDOS' sticker on the EPROM in the dongle.

A short inspection in a hex viewer shows that the order of code is really much different than in known ROMs (PM/1.02 to MG/1.13). It looks that BASIC is at the beginning and QDOS starts at $7000. At $0328 I spotted what appears the SuperBASIC startup windows and "splash" message:
CON_512x52A0x204_100 SCR_256x204 CON_256x204A256_50 CON_300x10A86x123_5 Press space for 256 mode, else return...

QLvsJAGUAR wrote: Sun Dec 22, 2024 8:59 pm
Chris, can you tell us the story of the purchase? Did you travel from Germany to England (Wolverhampton?) to meet the seller and collect the machine. Any anecdotes?

What is a shame, is that the buyer of the ROM port dongle is not (yet) known. He may not know that the content of that 27128 EPROM labelled QDOS 8000 13-2-84 is very important in respect to Sinclair QL history & software preservation.

Cheers, Urs

Well as you asked! I did indeed. I had planned to go over at the end of the year to visit mum as she had a funny turn on a train a few weeks ago and spent a few days in hospital. The whole visit was pretty much a nightmare though, due to the cold and the extra people everywhere at this time of year and every other one coughing and sneezing to some degree.

My flight from Leipzig way delayed by about an hour and when I got to the hire car place at Stansted they had all gone home! I was stranded without transport. Luckily I was staying the night somewhere local as I knew it would be late. I ordered a taxi to take me to where I was staying. I'd never been there before, neither had the taxi driver. It was a private house. The postcode was correct, the door number and door colour was correct, so I paid the man and he drove off in the same manor that he had got me to my destination (like a lunatic). I went to where I needed to go and then realised I was in the wrong place - right number, wrong road!

So I stood there with my suitcase in a strange road in a strange village and pondered over my life choices a bit. I attempted to use google to find out where I really needed to be, but to no avail as there was no internet, either due to network coverage or my phone getting confused after roaming and having the wrong SIM card enabled for data of whatever. I was cold, it was 1AM and I wanted to go to bed. I wondered up and down the road tugging my suitcase along and I found what I thought was probably the right house. A building in their garden was illuminated and I could see a bed through the window and the key to the door was in the lock on the outside. That was going to be my bed for the night no matter what! It was the right place and the owner was kind enough to take me to the car hire hut the next day but despite it only being 10 hours later than planned, they said the car I booked had gone and of course I had to do a deal on an alternative.

Car acquired, I drove up to Wolverhampton and collected the ZX83. No problems at all with that, it wasn't a bad drive and the seller was friendly (hello, if you ever see this). From there I went to mum's in Norwich. Felt cold to the bone for the next couple of days, noticed I was coming down with something on Tuesday evening, so stayed indoors and didn't really see anyone (sister, niece/nephew etc) and then I flew back home while feeling shit on Friday, trying to stifle coughs and sneezes. I hate travellers who travel while ill and I hated myself for potentially infecting others - selfishly. The cold was pretty mild though and it was either that or end up having to pay massive money to travel even closer to xmas or missing being home for xmas completely! The trip back was also packed with people, an hour waiting in the queue to get through customs (they seemed very understaffed), original train plans missed, got home at 22:30. The gf picked me up at the station and didn't recognise me instantly, said I looked like I'd aged 30 years since she had dropped me off there 6 days prior.

On the last train I folded down the Klappsitz and a new looking iPhone fell to the floor! I picked it up, it was of course locked. Unsure what to do with it, I took it home with the feeling that it would probably cause trouble in some way. It did. At 7 bloody 30 the next morning it's owner was outside ringing on the doorbell like a man possessed, after obviously tracking it down with GPS. I ignored it and he went away. Just before midday there was the same possessed iPhone-deficient doorbell ringing again and I'd just got out of bed, hadn't even done my hair. He stood at the door with his wife, obviously safety in numbers, in case I had nefarious plans for his iPhone. I explained I'd found it in the Klappsitz and told him I'd go and get it. He was grateful and gave me 20 Euros Finderlohn, which I gratefully accepted. We wished each other Merry Christmas and they drove off in a showy-off BMW.

I'm better now, mother in law is coming tomorrow, so that'll be fun.

The joys of QL ownership!