SGI O2 PROM flash chip location? - Printable Version
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SGI O2 PROM flash chip location? - mattst88 - 09-02-2018
The PROM code that initializes the system is presumably stored on a flash chip on the O2's motherboard. I've looked the board over and Googled a bunch of part numbers and nothing registered as a flash chip.
Does anyone know where this presumed device is on the O2 and even better what its model number is?
Edit: It's an Atmel 29C040A 4M flash chip hidden under the Dallas RTC.
RE: SGI O2 PROM flash chip location? - johnnym - 09-02-2018
(09-02-2018, 06:01 PM)mattst88 Wrote: The PROM code that initializes the system is presumably stored on a flash chip on the O2's motherboard. I've looked the board over and Googled a bunch of part numbers and nothing registered as a flash chip.
Does anyone know where this presumed device is on the O2 and even better what its model number is?
No sorry, not really, and I also don't have one of my O2s here for checking currently, but from looking at this picture and not spotting anything similar to a flash chip or EEPROM I know of, I'd say have a look under the NVRAM/RTC package, maybe its socket is around/on top of the flash chip or EEPROM of the O2.
You already checked the other side of the PCB, didn't you?
RE: SGI O2 PROM flash chip location? - BrainStorm - 09-02-2018
I have one of my R10k O2's guts out, at least to the extent of unlatching and pulling assemblies. I don't see anything that looks like an EEPROM. I also looked through the small gap at the underside of the logic board and I don't see anything bigger than SMD capacitors under there.
Maybe a non-re-programmable soldered PROM? Or maybe it's on the frontplane, if that's even a reasonable possibility.
I will note this though, The Dallas RTClock chip looks awfully big for what it is, and compared to the fairly small ICs that occupy the rest of the logic board. The password defeat jumper is also right next to it. Coincidence? or conspiracy?
RE: SGI O2 PROM flash chip location? - johnnym - 09-02-2018
(09-02-2018, 08:01 PM)BrainStorm Wrote: I will note this though, The Dallas RTClock chip looks awfully big for what it is, and compared to the fairly small ICs that occupy the rest of the logic board.I'd say this NVRAM/RTC has the usual size. As it is socketed, you can just remove it with a little force to have a look at the part of the PCB that's under it. But don't break anything if doing this.
(09-02-2018, 08:01 PM)BrainStorm Wrote: The password defeat jumper is also right next to it. Coincidence? or conspiracy?No, I don' t think so: the jumper next to the NVRAM/RTC is the "PWR UP" jumper. When shorted it makes the O2 start automatically as soon as power is supplied to the PSU. The password reset jumper is located near the memory module sockets.
RE: SGI O2 PROM flash chip location? - BrainStorm - 09-02-2018
You're absolutely right, it is the power jumper. I was just jacking around with it on my other O2 last week. lol what fun would life be without the occasional brainfart?
RE: SGI O2 PROM flash chip location? - Jacques - 09-02-2018
RThe prom chip is a XILINX chip located on the cpu board, not motherboard. Part reference XC1765ELS08C. It has 8 legs surface mounted to the pcb and sometimes has a little white label stuck on with a number on, not on my 300mhz R5200 board though
It nigh on unobtainable these days and the ones you can buy are usually flashed with previous garbage. Somebody in China sells them on ebay for about £30 for 5. You also need the Xilinx eeprom programmer @ about $150 if you want to flash a new one....last time I checked pricing. And if you're thinking of flashing for R7000 600mhz chip, you will need an the programmer with correct firmware and software otherwise you end up with an incorrectly flashed eeprom spewing out the wrong bitstream at boot time. :/ not sure about versions etc...
Did a quick screenshot and markup of eeprom location...
Hmm, can't upload image, here's a link
https://flic.kr/p/LWvGVa
RE: SGI O2 PROM flash chip location? - mattst88 - 09-03-2018
Quote:RThe prom chip is a XILINX chip located on the cpu board, not motherboard. Part reference XC1765ELS08C. It has 8 legs surface mounted to the pcb and sometimes has a little white label stuck on with a number on, not on my 300mhz R5200 board though
It nigh on unobtainable these days and the ones you can buy are usually flashed with previous garbage. Somebody in China sells them on ebay for about £30 for 5. You also need the Xilinx eeprom programmer @ about $150 if you want to flash a new one....last time I checked pricing. And if you're thinking of flashing for R7000 600mhz chip, you will need an the programmer with correct firmware and software otherwise you end up with an incorrectly flashed eeprom spewing out the wrong bitstream at boot time. :/ not sure about versions etc...
I knew about that chip, but I figured it just held the serial EEPROM (Called "Boot-Mode Settings" in the RM7000 manaul) that holds the 32-bits of data to configure the CPU. The image from Chicago Joe only really contains 32-bits of data. (That file is referenced in http://www.futuretech.blinkenlights.nl/o2cpumod.html but very confusingly has a different filename and is not linked from that page!)
Also, I seem to recall someone saying they couldn't get their R10k (or something) to work in an O2 with an old PROM version. If the whole PROM image were on the CPU board, that couldn't happen. Also, the XC1765ELS08C is a 64kB device.
I guess what I'm saying is that I doubt that is the chip that holds the 512kB PROM image
While we're on the topic of XC1765ELS08C, do we know of any suitable alternatives? Hopefully one that doesn't require a $150 programmer?
johnnym called it! I popped off the Dallas RTC and underneath found an Atmel 29C040A 4MB flash chip!
I'll edit my original post to save future readers some time!
RE: SGI O2 PROM flash chip location? - johnnym - 09-03-2018
(09-03-2018, 06:39 AM)mattst88 Wrote: johnnym called it! I popped off the Dallas RTC and underneath found an Atmel 29C040A 4MB flash chip!There you have it!
Educated guessing works - sometimes... 
RE: SGI O2 PROM flash chip location? - Jacques - 09-03-2018
I thought you were on about the eeprom to initiate the CPU boot calls. Yeah the other one is under the Dallas.
Sorry my bad!