ChanServ changed the topic of ##yamahasynths to: Channel dedicated to questions and discussion of Yamaha FM Synthesizer internals and corresponding REing. Discussion of synthesis methods similar to the Yamaha line of chips, Sound Blasters + clones, PCM chips like RF5C68, and CD theory of operation are also on-topic. Channel logs: https://freenode.irclog.whitequark.org/~h~yamahasynths
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<whitequark>
the problem i'm facing is that it doesn't boot
<whitequark>
i know there is power. i know the address pins are toggling, and on the internal data bus (not the ISA connector) the data pins are toggling
<whitequark>
it doesn't print a prompt on the UART and it doesn't respond to ESC
<whitequark>
i verified that the uC side of the level translator gets an ESC, and that there is no transmission
<whitequark>
i tried running it with autoboot on, with various W2 and W3 jumper settings, no change
<whitequark>
seems to have arrived to me in the factory configuration, memories wise
<whitequark>
i've extracted and reseated all the memories, no change
<whitequark>
there are no electrolytics on board and no oxidation anywhere i see, looks pristine, not even dusty (it was in a sealed case)
<whitequark>
even though it's like 23 years old
<whitequark>
not really sure what to do next
<TD-Linux>
if you have a way to dump the eprom, you don't need a very wide la for the address lines, as it's very likely looping over a small bit of code waiting for something to happen. might be informative on what's happening (this is how I fixed my pc-9821)
<whitequark>
oh
<whitequark>
well i could use glasgow :p
<TD-Linux>
glasgow even has enough lines to do all of them
<whitequark>
hrm
<whitequark>
it's a 8 bit EPROM
<whitequark>
so 8 bit data + uh
<TD-Linux>
oh, dumping the rom with glasgow
<whitequark>
needs a counter
<whitequark>
15 address lines + 8 data lines = sadness
<whitequark>
oh, i got what you meant
<whitequark>
the ROM is CAMBASIC IV V5.03
<TD-Linux>
cursed idea: lift the eeprom data pins and ground them, then the cpu will count up from 0 on reset due to executing nops
<whitequark>
:/
<whitequark>
it's a ceramic EEPROM
<whitequark>
EPROM*
<TD-Linux>
(actually though if you can find a 5v arduino or something it'd make more sense)
<whitequark>
oh i would just use a glasgow as a counter
<whitequark>
and then some dumb logic analyzer to capture the data
<whitequark>
then pulseview to convert it to a ROM dump
<whitequark>
so, A0..A9 are toggling
<whitequark>
... wait
<whitequark>
the other address pins aren't even connected on the ISA lol
<TD-Linux>
one other quick check is sometimes I've seen eprom data lines become "weak", where they don't drive voltages high enough. something you could quickly check with a rigol
<whitequark>
i actually did see something weird
<whitequark>
a bus driven like... halfway
<whitequark>
i wasn't certain which memory chip it is
<whitequark>
lemme desocket everything except for EPROM (again, sigh) and try it
<whitequark>
horrifyingly i think i am getting better at DIP extraction
<whitequark>
yep i am definitely observing this
<whitequark>
hmmmm
<whitequark>
i also see an obvious period
<whitequark>
though this is without RAM so that's expected
<whitequark>
wait, i should be looking only at parts where EPROM CE is active
<whitequark>
or i guess OE
<whitequark>
no, CE
<whitequark>
TD-Linux: this is really weird
<whitequark>
i.. think the pullups might not be working?