Difference between revisions of "128k on GX-4000"
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Leg 16 is used by the ASIC to select the RAM bank to use. All other signals are totally parallel. | Leg 16 is used by the ASIC to select the RAM bank to use. All other signals are totally parallel. | ||
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[[File:Piggy-backing-ram-pin16.png|framed|center]] | [[File:Piggy-backing-ram-pin16.png|framed|center]] | ||
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| + | '''3) Pin 16 of both ram chips must be connected to ASIC NCAS1 (pin 91)''' | ||
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| + | It is very easy to spot this leg, since it is the one just after the 90 written on the board, and it is not connected to anythin. (Beware, pin 89 just on the other side is a ground pin. Using it would select the RAM for all access and mess up everything. | ||
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| + | [[File:Asic-pin-91.png|framed|center]] | ||
Revision as of 09:20, 11 June 2022
Disclaimer: Adding ram to the GX-4000 is mostly useless. The only reason I did this is for fun...
1) Get two CPC-Plus compatible ram.
I used KM41464AP-12, but there are other chips of the same kind that should work.
2) Solder them both piggy back on the existing ram chips, except for the NCAS signal (pin 16)
Leg 16 is used by the ASIC to select the RAM bank to use. All other signals are totally parallel.
3) Pin 16 of both ram chips must be connected to ASIC NCAS1 (pin 91)
It is very easy to spot this leg, since it is the one just after the 90 written on the board, and it is not connected to anythin. (Beware, pin 89 just on the other side is a ground pin. Using it would select the RAM for all access and mess up everything.
