ZX81 ROMs 3 types?

[Fruitcake]

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]

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

[Fruitcake]

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.

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 Not just selling old items that might have been archived decades ago, but also brand new stuff...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]

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]

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!!


Nice to see you're still around.



Regards.

Moggy.

[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!

[1024MAK]

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

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

Mark

[stroebeljc]

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.
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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.