Quoted from zacaj:
Trying to get a system 7 mpu booting, and I'm getting various 'bad RAM' readings.
Leon's test rom locks the leds on immediately, but does not display 1,2, or 3 (which according to http://pinball.flippers.info/system6repairpart4.asp it should). Two leds no flashes indicates the IC13 RAM is bad.
Andre's test rom blinks on 2 and 3, signifying that IC16 and IC19 are bad. Doesn't blink on 1 (IC13).
Usually I find these tests pretty good on system 3-6 games, but I've never had a system 7 ram issue before. My confusion lies in the fact that IC13 and IC16 are different on system 3-6 vs system 7. on 3-6 they're the lower halves of the first 255 bytes of ram. on system 7 they each span the whole 255 bytes but each are only four bits. Both these test roms claim to work for system 3-7, so how can you tell which RAM on a system 7 is actually bad? It seems like if it just scans the full bytes (like it would for system 3-6) then it wouldn't know which chip it was that caused the error? A look at the source code for Andre's seems to read like it only scans full bytes, and thus won't produce accurate results on a system 7, but I may be misunderstanding...
Can anyone confirm how to read these?
Would marco's rom work better? I've never used it
Is the system 7 self test more reliable than the system 3-6?
The 2114 RAM are only four bit wide parts.... but they are longer. 6810 chips are eight bit wide, but shorter in length.
Think of both the 2114 chips to be in the same address space, basically same chip. Then they combine the two 6810s together to get one long chip. Its like the cut width in half and then made it twice as long....
Because of this i'd expect odd results from RAM tests for system 7. Either 2114 being bad should result in Andre's or Leon's test to repair fail at BOTH spots if I am thinking about it right.