Testing GTIA

[madgitty]

Hi Guys

Just bought a couple of 130xe and 65xe pal versions, reading up on faulty gtia chips,as there is no serial number sticker underneath how can I test it to see if they are faulty.

I have found a basic prog which I tried and found that I get black lines in the pic, is this write

 

10 GR. 9:D=1:FOR X=0 TO 79

20 COLOR C:C=C+D:IF C=15 OR C=0 THEN D=-D

30 PLOT X,0:DR. X,191

40 NEXT X

50 G. 50

 

 

many thanks

[w1k]

try SYSINFO

 

http://drac030.krap.pl/en-si-pliki.php

si224.zip

Edited January 16, 2015 by w1k

[Rybags]

Black appearing at certain luma transitions is normal - it's because a resistor ladder is used to generate the signal. The problem there being that it takes time for voltage to ramp up when changes like 7 to 8 occur... in binary that's 0111 to 1000 - monentarily there's no voltage at all.

 

Bad GTIA will look like the GTIA modes don't even exist. In that program put an extra line in:

45 POKE 623,0

 

it makes the graphics revert to just normal mode 8 - I've got an 800XE which is a victim of the bad batch of GTIAs.

Edited January 16, 2015 by Rybags

[madgitty]

sorry to be thick, how do I run the file as it is a .arc

thanks

Edited January 16, 2015 by madgitty

[russg]

sorry to be thick, how do I run the file as it is a .arc

thanks

It is a .atr. .arc is a compression format. .atr is a disk image. you can use an .atr in emulator, or to use it with a real atari, you

need APE or ASPEQT disk drive emulator on PC and a PC to Atari interface and PC to Atari cable, either USB or serial.

There is a file called SI2.EXE on the .atr. That is what you run.

Edited January 16, 2015 by russg