ZX81 ROMs 3 types?

Discussions about Sinclair ZX80 and ZX81 Hardware
Fruitcake
Posts: 346
Joined: Wed Sep 01, 2010 10:53 pm

Re: ZX81 ROMs 3 types?

Post by Fruitcake »

1024MAK wrote: Sun Apr 25, 2021 4:03 pm So it is still surprising that this was not previously known about...
And not referenced in any publication (I have seen) from the time, and yet someone appears to know detailed information about why and when each ROM was released... Where did they get that information from? Who would know such detailed information?
Lardo Boffin
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Re: ZX81 ROMs 3 types?

Post by Lardo Boffin »

Fruitcake wrote: Sun Apr 25, 2021 4:16 pm
1024MAK wrote: Sun Apr 25, 2021 4:03 pm So it is still surprising that this was not previously known about...
And not referenced in any publication (I have seen) from the time, and yet someone appears to know detailed information about why and when each ROM was released... Where did they get that information from? Who would know such detailed information?
I have asked the seller. Hopefully they will get back to me.

Looks like they are Sinclair fans?

https://www.ebay.co.uk/itm/ZX80-ROM-ADA ... 890.l49286
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
Fruitcake
Posts: 346
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Re: ZX81 ROMs 3 types?

Post by Fruitcake »

Lardo Boffin wrote: Sun Apr 25, 2021 5:33 pm I have asked the seller. Hopefully they will get back to me.
Was thinking to do the same but don't want to flood them with such queries so will will wait to hear if they respond to you.

Lardo Boffin wrote: Sun Apr 25, 2021 5:33 pm Looks like they are Sinclair fans?
https://www.ebay.co.uk/itm/ZX80-ROM-ADA ... 890.l49286
Yes, that is interesting also. Not just selling old items that might have been archived decades ago, but also brand new stuff...
balford
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Location: Dublin, Ireland

Re: ZX81 ROMs 3 types?

Post by balford »

Heh, I considered myself fairly well informed about all things Sinclair and I didn't have a clue about the intermediate ROM!

It seems uncommon rather than rare though, out of 14 Zeddys I own, 3 of them have the 622 version.

If we're talking dates, then on my machines they occur on machines with a ULA date range between 8128 and 8140. Obviously up to now people have paid more attention to ULA date codes than anything else :)
Moggy
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Re: ZX81 ROMs 3 types?

Post by Moggy »

Hey up Balford long time no hear!!

Do you still have that Issue one ULA I sent you?

If I'd have realised that postage to your part of the world was so expensive I'd have hired a container and sent you my whole bloody collection!! :lol:


Nice to see you're still around. :D



Regards.

Moggy.
balford
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Joined: Tue Dec 03, 2013 11:20 pm
Location: Dublin, Ireland

Re: ZX81 ROMs 3 types?

Post by balford »

Nice to see you too Moggy, I dip my toe in now and again :)

I certainly do still have that 2C158E, providing sterling service to this day in a kludge ROM Zeddy!
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1024MAK
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Re: ZX81 ROMs 3 types?

Post by 1024MAK »

Um… wind back to the year 2010, and read this topic:shock:

See also the “what ROM do I have?” topic here ;-)

Mark
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stroebeljc
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Re: ZX81 ROMs 3 types?

Post by stroebeljc »

jeep wrote: Fri Feb 12, 2021 2:24 pm Thank you for this useful information, it confirmed some assumptions that I made and the ROM dumps were invaluable.
I can't believe that this was discussed so recently either, I had gotten used to dead links and having to use the wayback machine to find information.
.
.
.
The oddities that I'd seen in the spectrum port were bug fixes (I've not done a full comparison yet) and there was a bit of code checking a part of ROM. I'm guessing that people may be interested in seeing the code, so here it is.

Code: Select all

493c : e5           push hl             ;  
493d : d5           push de             ;  
493e : c5           push bc             ;  
493f : 01 00 80     ld bc, 8000         ;  
4942 : 3a 36 00     ld a, (0036)        ;  
4945 : fe 84        cp 84               ;  Version 1 of ROM?
4947 : 20 09        jr nz, 09 (4952)    ;  Jump if pause bug has been fixed
4949 : cd 32 0f     call 0f32           ;  ROM: Set Fast and Pause
494c : fd 36 35 ff  ld (iy+35), ff      ;  Set high byte of FRAMES
4950 : 18 03        jr 03 (4955)        ;  

4952 : cd 35 0f     call 0f35           ;  ROM: Pause
4955 : ed 4b 25 40  ld bc, (4025)       ;  System Variable: LAST-K
4959 : cd bd 07     call 07bd           ;  ROM: Keyboard decode
495c : 7e           ld a, (hl)          ;  
495d : c1           pop bc              ;  
495e : d1           pop de              ;  
495f : e1           pop hl              ;  
It now makes perfect sense, so thank you again. I guessed that it it must have been a check for different rom versions, but to find this thread where people had recently discussed the bug fixes was very satisfying. I'm not the only one looking at 40 year old technology to see how it ticks!
The check for 84h is against the original ROM version, which (as I understand it) does not contain the pause bug. Versions 2 (with pause bug) and 3 (fixed pause bug) both have 88h at this location. So, this code is not detecting the pause bug, at least if running on Version 2 ROM.
John
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