Found this in a copy of Sync magazine (page 9) and wondered which of the early ROMs ROM it refers to (550 or 622.) unable to test myself as all mine are fitted with Big Bang EPROMs which show 2^32 in E notation anyway.
https://archive.org/details/syncmagazin ... ew=theater
Another way to test for a bugged ROM apparently.
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Re: Another way to test for a bugged ROM apparently.
Using Kevin‘s excellent ZX81 emulator for iOS powered iPhones and iPads, I can confirm only the ‘550’ ROM (the first ‘bugged’ version) gives the screwy result.
The 622 and 649 both give the expected result.
Mark
The 622 and 649 both give the expected result.
Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp
Standby alert
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer later in the year.
Re: Another way to test for a bugged ROM apparently.
550 is the original ROM (the "unimproved" ROM), and it had several major bugs
622 is the "improved" ROM, which fixed those. However, 622 introduced a minor bug, which was then fixed in 649. As I understand it, 622 is the most infrequently found version as it was updated quickly on the production line
Bugs in 550
* INPUT bug
* Syntax checking bug
* The floating point bug ("maths" bug)
The method of checking the FP bug doesn't always work -- if the Sinclair assembly-line fix has been applied, even if the machine still has the 550 ROM
I'm guessing this is what the article from Sync January/February 1982 Volume 2 Number 1 is about?
* PAUSE bug, but only in SLOW mode and only then sometimes
See ZX81 ROMs 3 types
622 is the "improved" ROM, which fixed those. However, 622 introduced a minor bug, which was then fixed in 649. As I understand it, 622 is the most infrequently found version as it was updated quickly on the production line
Bugs in 550
* INPUT bug
* Syntax checking bug
* The floating point bug ("maths" bug)
The method of checking the FP bug doesn't always work -- if the Sinclair assembly-line fix has been applied, even if the machine still has the 550 ROM
I'm guessing this is what the article from Sync January/February 1982 Volume 2 Number 1 is about?
Minor bug in 649Sinclair 8K ROM Problems?
In SYNC Notes {SYNC 1 :5) we gave a test to check whether you had received a defective ROM. The following letter from Nigel Searle will clarify this matter further:
Dear Customer:
The recent mention in Sync magazine of a possible bug in our 8K BASIC ROM could be misleading.
The correct value of 2^32 is 4,294,967,296. This is rounded to 8 significant digits and displayed as 4,294,967,300. 2^32-1 is 4,294,967,295 which, when rounded to 8 significant digits, is also displayed as 4,294,967,300.
This is the appropriate result for a computer of finite (8 digit) capacity.
The bug referred to in Sync will give 1,288,490,200 when 1 is subtracted from 2^32 (4,294,967,300). Only if your ROM has this problem should you return it to us for replacement.
Nigel H. Searle
* PAUSE bug, but only in SLOW mode and only then sometimes
See ZX81 ROMs 3 types
Re: Another way to test for a bugged ROM apparently.
QUOTE.
Minor bug in 649
* PAUSE bug, but only in SLOW mode and only then sometimes...
There is no PAUSE bug in 649, only the first two ROMS and then only in a certain set of circumstances in my experience.
Minor bug in 649
* PAUSE bug, but only in SLOW mode and only then sometimes...
There is no PAUSE bug in 649, only the first two ROMS and then only in a certain set of circumstances in my experience.
Re: Another way to test for a bugged ROM apparently.
thanks, i had a typo. i meant to write that 622 had the PAUSE bug, and 649 fixed all the bugs
to recap:
555 is the "unimproved" ROM
622 and 649 are the "improved" ROMs
to recap:
555 is the "unimproved" ROM
622 and 649 are the "improved" ROMs
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Re: Another way to test for a bugged ROM apparently.
See also this post:
https://sinclairzxworld.com/viewtopic.php?f=7&t=4721
where the 622 was found found in all 9 (at time of writing) of the beige / yellow / cream PCB issue one zeddies I have bought.
https://sinclairzxworld.com/viewtopic.php?f=7&t=4721
where the 622 was found found in all 9 (at time of writing) of the beige / yellow / cream PCB issue one zeddies I have bought.
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
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
Re: Another way to test for a bugged ROM apparently.
I would say that the 649 was the least produced as the zeddy was more or less at end of life production by this time.
Re: Another way to test for a bugged ROM apparently.
good to know. i write these out so i can remember and it's only partially working