Disabling a ROM chip?

[Raccoon Lad]

I want to try a hack on a spare SMS unit. The hack is basically disabling the BIOS so Sg-1000 My cards can be played on a US SMS.

Now, I don't really know how to do this, but I'll try anyway.

From what I've gathered on the information super garbage dump, is that I probably need to disable the bios chip by using either the CE (Chip Enable) or OE (Output Enable) pins.

Would tying CE to +5v do the trick?


Anyone?

[Bratwurst]

Would tying CE to +5v do the trick?

That generally activates the chip, you'll have to leave CE floating (off state), maybe cutting the trace to it (or introducing a switch in the circuit).

Incidentally, concerning your other idea of rendering a Game Genie into a Power Base Converter, you may want to try acid etching your own PCB that will fit into the Genny cart port and extend to the SMS card edge connector or however the design is supposed to work out. Did you actually find some SMS card edge connectors btw?

[Raccoon Lad]

Really, everything I've seen would seem to indicate CE and OE are enabled by being tied to ground, and disabled by tying to +5. I guess i can try it both ways, the worst I can really do is end up killing an extra system that didn't have any hookups anyway. (besides, I got it for free)


And for the Game genie thing:

a SMS card edge connector is a basic .1 inch (2.54mm) pitch 50 pin card edge connector. lots of places have these.

I'd use a Game genie because the case is perfect for what I want to do, and I can use the pins from the game genie. (I suppose I could also use a Sonic&Knuckles, but I hate killing fun carts)

Here's the PCB for a Master Mega adapter (as supplied by some nice european guy): http://cgfm2.emuviews.com/img/master-mega-converter-mb01.jpg
http://cgfm2.emuviews.com/img/master-mega-converter-mb02.jpg

it's damn simple inside, so I figure all I'd have to do is just cut the game genie PCB in half, glue the SMS edge connector into the case, and do a little re-wiring.

shouldn't be too hard.

[leonk]

Why not do something simpler? Find out which pin is Vcc (5V) and just lift it? No power, no TSOP.

[omnedon]

^^

That's what I was thinking.

[AlanD]

You are correct. Generally the OE or CE are active low and high for inactive state. Best bet in my opinion is to pull the pin for the chip enable and wire it to +5. Don't just jump the +5 onto the pin still hooked to the board as it may have some unexpected results for other chips. Don't know without a schematic but pretty easy to just pull the pin. Also just pulling the power is not a good solution as you still have the address and data pins on the bus in unknown states. Could cause weird side effects too.
Alan

[Raccoon Lad]

Well, pulling the VCC didn't give me the desired effect. (just got a black screen)

I guess I'll have to try again with the CE next time.

[Lost Monkey]

Any confirmation on whether this mod is possible?

[Raccoon Lad]

Just for the reccord, pulling CE gave me nothing as well.

So despite Bock's (SMSPower) insistance that disabling the BIOS will allow playing import MyCards, the system seems to need the BIOS chip connected to run.

[rbudrick]

Maybe a switch for it would be best...Maybe you could start it with the bios and then switch it off...I've heard of similar hacks for other systems.

-Rob