two flash chips and remove original bios

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(08.06.2012 18:28)johnriper писал(а):  

(08.06.2012 12:43)SWAT писал(а):  Of course you can do it!

can i have a little help with scematics?
in both chips do i solder together pin 1, 23 and 44 and select to boot with seperate 12 pin?
thanks.

I have done this and it is possible but can be very problematic unless you are good at this kind of thing. I consider myself average and managed to kill two boards doing the double mod, whilst I had no issues with the normal piggy back mod, done that a few times now.

To be honest, now that I ave done it I have found it to be less useful than I anticipated. Many ISO's just won't run so well from the bios boot. For example I can't get the Atari 7800 emu working properly from a bios boot or the Amstrad emu, which runs without sound, but they both work fine if booting Dreamshell with a disc. Similary, a lot of official games don't work well either. Hopefully these issues will be resolved in the future, which would make it very worthwhile having a dual flashable bios.

In terms of the schematics, you can simply solder all legs (except leg 12) to the board and then join all legs of the second chip (except leg 12). Legs 1 & 44 apparently have no use so you can have them up or down..it doesn't really matter. After that just follow the usual guide and select with a switch using the leg 12 on each chip

Hope this helps

Cheers