Wierd Commodore 64 rom mod

[pc_91]

some days ago i've got a boxed C64, the Drean version, only sold in argentina, also have the C128 of this version, it came with the datasette and the printer, pacmania and poleposition on a forgotten tape on the datasette, i didn't expect it to work since it was stored like 15 years, so i hooked up and fired it, light blue screen comes up with correct borders but full of garbled text and didn't responding to keyboard, tipical rom error, so i opened the machine to reseat the ICs when i found out some wires running on top the rom chip and 2 legs from each side getting out of the socket, maybe the rom was replaced and had to put a similar chip with diffrent pinout maybe? after reseating the IC the machine worked flawlessly, even loaded the games on the tape, the pacmania was a cracked version with unlimited lifes as an option, anyway, here are some pics.

[XxHennersXx]

...weird.

It functions same?

[Jamtex]

The 2364 Mask ROM has less pins and a slightly different pinout to the 2764 EPROM, so to make it fit you need to make a adapter or do the funky lift pin legs up and solder them to the board routine. I doubt if the ROM is any different in terms of code.

http://ist.uwaterloo.ca/~schepers/roms.html

A webpage showing you how to burn EPROMs for use in various commodore machines.

[APE]

Looks like an OTP EPROM that needed a bit of rewiring in order to be compatible. Unless it is some custom/modified BIOS I wouldn't call it weird.

EDIT: Looks like Jamtex beat me to it.

[pc_91]

yes, is the same rom, or at least what i can test, it's wierd to me that someone had rewired it instead of buying the replacement rom since in argentina was an oficial reseller and service of comodore, and how the hell did someone manages to destroy the mask rom without destroying everything else? maybe is a custom rom, dunno how to note if diffrent.

[Guaripolo]

is this the drean version or a import one?

(that chip looks weeeeeeeeeiiirrdd!!)

[pc_91]

the machine is import as it looks like, but the c128 is the drean and has the original import sticker, this c64 has only the import sticker, maybe the drean was removed, the psu says drean, plus the import version has a metal shielding while this and the drean has a silver cardboard shielding, real cheap, so i guess is a drean one

[LocalH]

That looks like it's the KERNAL ROM. Grab a tool (or write one in BASIC, if you need me to I can do so) and dump $E000-$FFFF to a file, and it can be compared to stock KERNAL ROM images.

[pc_91]

i like your idea, but how can i transfer the file generated since i only have the datasette?

[LocalH]

I'm pretty sure there exist tools that can take WAV files sampled from a C64 tape and output binary files.

This BASIC program should write an 8192 byte file to tape named "KERNAL". It's been a while since I've done this with a tape though, so if someone else sees any errors then please let me know:

5 OPEN 1,1,1,"KERNAL"
10 PRINT"{clr}WRITING 8K AT $E000 TO TAPE."
20 FOR X=0 TO 8191
30 PRINT#1,CHR$(PEEK(57344+X));
40 IF (X/256)=INT(X/256) THEN PRINT X;" BYTES WRITTEN."
50 NEXT X
60 CLOSE 1

Obviously you'll need an audio tape with which to record the output of this program. As for actually converting the recorded tape to a binary, I'll have to get back to you.

[pc_91]

niceeee, in somedays i'm gonna have a TV (yes, i don't have a TV) so i gonna test it, i got the necesary to dump the resultant tape so i send it to you to binaryze it, as soon as i have the TV i test it

[LocalH]

Ok, updated the post, had a slight bug in line 30 (was adding the loop index to the value read from $E000, rather than adding the loop index to $E000, this would have crashed at most on the 256th iteration and maybe sooner :P)

[pc_91]

one question, it will automatically prompt me to press the rec button and that or how is it going to do?

[LocalH]

To be honest, it's been so long since I used a Datasette that I don't remember. By default, the C64 turns off the motor though, so I recommend just pressing record before running the program.