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Author Topic: BIOS questions  (Read 586 times)
kokkiklhs
Trying to get the cartridge in...
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« on: June 26, 2018, 10:40:06 AM »

Just out of curiosity:
In case the 8048 fails in a G7000/C52, can it be directly replaced with a stock 8048 off e.g. ebay?
I read that the BIOS of the machine is factory-programmed inside the microcontroller, so I assume that replacing it is not that simple!
Another thing, my french C52 displays the message "Quel Jeu?" upon startup with a cartridge inserted. Can this message be altered to "Select Game" or whatever, using the same IC that's already inside the machine?
Can someone explain the required procedure in detail?
Thanks!
 Huh?
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VideopacBelgium
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« Reply #1 on: June 26, 2018, 05:33:10 PM »

http://videopac.nl/forum/index.php?topic=1043.0
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kokkiklhs
Trying to get the cartridge in...
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Posts: 17


« Reply #2 on: June 27, 2018, 01:58:51 PM »


Thanks, I've seen this one already but it doesn't explain the whole procedure of programming the 8748, in detail!
I'd like someone in here who has already tried this, to describe it here as well as possible.
Equipment used for programming, the exact place/address to inject the BIOS into the new chip etc.
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VideopacBelgium
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« Reply #3 on: June 27, 2018, 05:15:26 PM »


Thanks, I've seen this one already but it doesn't explain the whole procedure of programming the 8748, in detail!
I'd like someone in here who has already tried this, to describe it here as well as possible.
Equipment used for programming, the exact place/address to inject the BIOS into the new chip etc.

You must contact member "gertk".
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kokkiklhs
Trying to get the cartridge in...
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Posts: 17


« Reply #4 on: June 28, 2018, 10:34:58 PM »

Nice suggestion, I'll have it in mind!

But if gertk reads this, it would be very useful to provide this info in public to the O2/VP community, for anyone else except of me who'd like to know!
 Cool
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gertk
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« Reply #5 on: July 02, 2018, 10:04:53 AM »

For programming a 8748 you need a suitable programmer (duh..)
My ancient Digelec 824 programmer can handle it (it has the correct rompac).

Changing stuff in the 'bios' is not very hard, just change some values with a hex editor and you can have for example a new startup text.

With a ceramic 8748 you can UV erase the contents and reprogram it.

Note: there are also 8748 in plastic casings without a UV erase window, these can only be programmed once! They are called OTP chips (One Time Programmable)

I use an emulator to see if the new contents works ok before 'burning' it into a real 8748.
You might need to fiddle with the source of the emulator to make it recognize your rom image as the checksum will be different from the original.

Another thing to consider: if you change the layout of the 'bios' rom routines there will be a big chance that many games will not run anymore. So be careful with that. Changing the startup text (both on G7000 and G7400) did not interfere with the functioning of any game I tested so far.
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>>G7000 G7200(P+S) G7400 N60 JET27 VG5000 ZX80 ZX81 ORIC-1 COMX35 Aquarius<<
kokkiklhs
Trying to get the cartridge in...
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Posts: 17


« Reply #6 on: July 02, 2018, 11:36:47 AM »

Nice, thank you, pal!
 Cool
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