PROBLEM FIXED!!! another dead bird has Rised!! probelm were, replace basically the entire motherboard IC's
main problem was jumping pin 7 (CIIN-) on jumper pad and replacing 2 Buffer/Drivers, and whala!! presto she woke up! Anyhow i want to thank Rodolphe P., Exxos, DML, Calimero, if it was for you guy's this bird might of never have risen!you guys are my hero's thank you thank you greatly my deer friends!!! 8 months of debugging and countless hours of troubleshooting! i guess i can proudly say i am a die hard Atarian!
Hopefully all ya all are still around
One, recently sold a "dead" Falcon motherboard to a guy in So Cal, wondering if you were the buyer Paul?
If so, have a lot of information to share
Know one of the first things going on according to the FSM is the cartridge port is checked for a "magic" number. If- else, boots from ROM.
Been working on a board, one of the last issues were with the FPU. Booting with a diagnostic cart, the first check on the screen is to initialize the FPU.
Scenario on this Falcon:
No FPU installed, diagnostic reports not found and continues to execute to menu.
FPU installed, FPU clock supplied from 32mHz oscillator (NTSC machine).
Diagnostic initializes FPU, continues to execute to menu.
FPU installed, no clock present. Diagnostic fails FPU initialization, reports two bus errors with accompanying red display, continues to execute to menu.
Pertinent to this old thread, is under diagnostic boot, FPU is first on the list to be initialized.
I'm not clear on what "pin 7 on jumper pad" is. You mean U46 or U47?
Which buffer/driver id's were replaced?
Why do I have the FPU clocked at 32 mHz from the main oscillator?
Well, this all started after what was supposed to be an easy job removing an Eagle Sonic card.
Some of the mods to the Falcon are similar to an AB or Mighty Sonic installation, topic here pin 16 and pin 17 of the Falcon SMT CPU are lifted off the solder pad, one jumped to ground and the other left to float.
I'd resoldered pin 16 and 17 of the CPU back to their pads. Cleaned up some other areas and confirmed the machine to boot.
Without doing any other testing, moved forward installing an exxos clock patch, as this machine didn't have one.
Rebooted after the installation without issue. (Thanks to exxos for making available a clean little non-intrusive board
to simply implement the patch). Other than the CPU pin mod, this is a virgin board, nice to keep it clean.
Didn't take long running through various programs, where it was know which IC's are being accessed or used for processing, for the newspaper in the bird cage to get real dirty
For a change of pace, decided to approach the problem with some semblance of methodology
Back to the FPU. I traced out the FPU/DMA clock lines from R221 to the FPU socket, from there to clock in of the DMA. Checked against for shorts between as many traces as possible, and shorts to ground. Verified C208 on the underside of the main board is not installed. Without a scope, cannot verify the 16mHz COMBEL clock to the FPU/DMA line, however with the FPU removed from socket, DMA is functioning.
What I haven't been able to resolve is why the FPU errors and is either not initialized, or is the cause of bus errors. Various FPU test and programs all fail with the FPU in the socket being fed from R221. If an FPU is installed where the clock in pin does not make contact with its socket, and fed from a different clock source, everything is peaches and cream.
I didn't at first treat this as a separate issue, until when back tracking discovered my solder work on pin 16 of the CPU was pretty bad, in fact, the CPU pin was just floating. I'm sure this caused all sorts of bus errors, as after poking at the same little thing with three types of flux, and a tip near twice the size of the pin about 30 times finally yielded a satisfactory solder joint.
Booted back up (this Falcon NEVER requires a reset, always boots first time every time) and started the same test process without any errors. Ran the piss out of the diagnostic cart with flying colors, some test several times.
So went back and revisited the FPU issue hoping that too had been resolved.
Nope, exact same situation as described above.
So for now, have left the FPU clocked aside from the clock patch feeds and view it as an individual problem.
If not for that, ALL I'd have to do to make this an awesome stock machine is to install a new NVRAM
Hope this either enlightens, confirms, provides solidarity or humor for other users
Throughout all of it, learned a lot about the bus PALs and GAL. Someone correct me if my memory is bad, seem to recall Cubza during the early phases of the CT60 consider removing them completely. For whatever reason, he didn't go that way, maybe because they actually do a good job of glueing board components together in simple fashion, and wasn't worth effort to integrate into his design. That's cool, with little effort, address pointers cold be changed to say, where a DSP is located on the Falcon