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Different ZX81 ROM versions ?
Posted: Wed Mar 14, 2012 3:46 pm
by PokeMon
If I use functions or code from ZX81 rom, I just want to know if there are complete different ZX81 rom versions with other code or other procedure addresses.
Or is it safe to assume, that the following listing is valid for all ZX81 (including first versions on the market) ?
http://www.wearmouth.demon.co.uk/zx81.htm
Re: Different ZX81 ROM versions ?
Posted: Wed Mar 14, 2012 4:20 pm
by sirmorris
ZXpand's ROM has a few things moved around. Nothing major though, and compatibility has been near 100% so far with everything I've tested.
C
Re: Different ZX81 ROM versions ?
Posted: Wed Mar 14, 2012 6:54 pm
by PokeMon
I use following entry points now in Basic:
;; N/L-ONLY
L0413:
;; SLOW/FAST
L0207:
Want to be sure that it works with all Zeddys.
What does ZXpand ROM exactly ? Does it disable the internal ROM and ZXpand ROM is used only ?
Re: Different ZX81 ROM versions ?
Posted: Wed Mar 14, 2012 7:19 pm
by sirmorris
Those entry points should be the same on all known ROMs, including ZXpand.
The ZXpand disables the internal ROM for anything other than character generation.
C
Re: Different ZX81 ROM versions ?
Posted: Mon Mar 19, 2012 4:28 am
by MOB-i-L
There is an 'unimproved' ZX81 ROM. It has some bugs: e.g. SQR has errors and PAUSE sometimes crash the computer. I have the unimproved ROM in my ZX81 that was bought in December 1981. I also have the rom-file. Search for unimproved in the listing you referred to - it is mentioned once but that file generates the improved ROM. (There is also the old ROM meaning ZX80 ROM.)
Re: Different ZX81 ROM versions ?
Posted: Mon Mar 19, 2012 4:44 pm
by PokeMon
MOB-i-L wrote:There is an 'unimproved' ZX81 ROM.
This is just one byte I think.
What I wanted to know is if there are different memory locations for some routines.
Anyway found a method of using RST $08 for jumping back to BASIC from the fastloader.
So this won't be changed ever in any version I think.
