(Topic ID: 230519)

System 7 test rom RAM tests

By zacaj

5 years ago

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10 posts
4 Pinsiders participating
Latest reply 5 years ago by OHMI_Arcade
Topic is favorited by 3 Pinsiders

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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?

Quoted from barakandl:
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.

Thats what I would expect for a system 3-6 test being used in a system 6, but both my roms specifically say they support system 7? And Andres is saying one 2114 is good and one is bad?

Quoted from barakandl:
Instead of an entire bad chip it could just be detecting one or a couple bad bits somewhere and it plots out the location based on sys 3-6 layout which may not match system 7.
Andre's ROM has no way to detect system 3-6 vs sys 7. I am going to assume the RAM tests are based on the layout of system 3-6 games which isnt going to line up properly to system 7.
I'd honestly pull the most suspect chip out and test it in a RAM tester than do the other other if the first one pulled wasnt the bad RAM.

None of the rams on any of my system 7s are socketed, so I can't test. Going to just have to remove and socket one by one, and have new rams on standby

Or maybe I'll just write a system 7 ram test rom...

Quoted from barakandl:
Try the real sys 7 flipper roms. As long as it boots up somewhat I'd trust that ram test more than leon or Andre

So those are more reliable? I've heard that the sys3-6 ones can't really be trusted. I tried them and got a 2, which again points to one of the RAMs

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