Reading Eproms Help!

[CHRIS-F]

Hi Guys,

I have a problem with my City Connection (bootleg) PCB and although it's probably not related to the EPROM's I thought I would remove them and read them just to make sure, I also like learning this stuff so doing it just for the sake of learning at the same time. I have the XG ecu TL866 II+ programmer and when i came to read the EPROMS's I got as far as doing the Fujitsu MBM 27256 -25 IC's for C1,C2,C6,C9 and the MBM 2764-30 for C13, but my programmer doesn't have an IC to select for the Hitachi HN 4827 128G-25 IC's C3,C7,C8,C10, the Toshiba TMM 27256D-20 for IC C11 and the Intel D2764-3 for IC 12.

How do I go about reading theese IC's is there an equivelant I can select or can i add them to my programmer some how, or does my programmer just not do those IC's.

Also I think i read somewhere that it is a good idea to dump the image a few times and compare them, i tried a diff program online but it only done part of the image, is there a way to check them against known good dumps etc.

Thanks guys
Chris.

[lilshawn]

though the part numbers are weird, they should all just read same as a generic 27 series chip. find yourself any manufacture 27C64, 27C256 or whatever part numbers they say they are... the number after the C is the size and just match it up to the number after the 27. 27C64,128,256,512 for under 1 meg chips... or numbers like 27C010, 040 080 for over 1 meg sized chips.

so a 2764 turns to 27C64
and a 27256 a 27C256

same with the weird Hitachi part numbers... 4827128-25 becomes 27C128 the -25 is the rated speed which is not important here unless you are swapping them out.

just keep an eye out for binary multiples1,2,4,8,16,32,64,128,256,512. and slot them into your 27C series part numbers.

[CHRIS-F]

though the part numbers are weird, they should all just read same as a generic 27 series chip. find yourself any manufacture 27C64, 27C256 or whatever part numbers they say they are... the number after the C is the size and just match it up to the number after the 27. 27C64,128,256,512 for under 1 meg chips... or numbers like 27C010, 040 080 for over 1 meg sized chips.

so a 2764 turns to 27C64
and a 27256 a 27C256

same with the weird Hitachi part numbers... 4827128-25 becomes 27C128 the -25 is the rated speed which is not important here unless you are swapping them out.

just keep an eye out for binary multiples1,2,4,8,16,32,64,128,256,512. and slot them into your 27C series part numbers.

Hi Shawn,

I followed your advice and chose a similar part no from other manufacturers and 12 of the 13 EPRoms read perfectly and are an exact match to the City Connection set1 ROM's from MAME, I compared them using a DOS binary file compare program. but the remaining EPROM, IC'11 which i think was a Toshiba TMM 27256D -20 gave a few different results of just a few bytes reading them with different manufacturers, I did manage to get about 6 consistent reads using 6 different manufacturers, so I went with one of those reads, only problem is when I compared my IC11 to the MAME IC 11 the results are way different, I can't see how many differences there are as the dos screen wont scroll back far enough, but its hundereds of differences if not thousands.

I've asked this in another thread about fixing my PCB but is it normal for a bootleg PCB to have different ROM contents to an original board or does it sound like somehow my IC11 has been corrupted even though it worked before going into storage.

I can't even check my ROM in mame because of all the CRC checks etc, I did try making a zip of my ROMS but MAME just tells me there are required ROMS or CHD missing, if I replace my IC11 in the ZIP with the one from MAME it does run perfectly so at leas I know all my other ROMS are OK.

Assuming the bootleg ROM is different, is there anywhere I can find a bootleg ROM to compare agains my own?

Thanks,
Chris.

[lilshawn]

bootlegs will typically have different rom contents it's usually not much (a copyright message or manufacture, year etc.)

the bulk is the same