Bug in Intel Atom C2000 series processors?

[cj1]

the (5) pullups around TPM are connected is same as the pin 9

What do you mean with "pin 9" in this context? +3V ?



For every ones information here is a photo of the C2750D4I rev 1.02 mainboard under the CPU position before the AVR repair, with the to be repaired spots marked:

 

[RZSN]

What do you mean with "pin 9" in this context? +3V ?

Yes, the trace which the resistors connect to - has the same voltage as the TPM Pin 9 (+3V is a typo, it is actually a normal +3.3V rail), which measures on my board +3.456 V. That is different from the +3.3VSB (pin TPM 15), which is powered also in power off (standby) state.

I have to fix my previous info: the trace is not directly same as +3.3V rail, as it connects to a resistor near the two jumpers on the top side of the PCB, but I am unable to trace its source nor destination.

 

[cj1]

It seems that all of the resistors are marked 12A but ohm out around 130...

According to kiloohm.info/eia96-resistor/12A resistors marked with "12A" are in fact 130 Ω / 1% resistors.

So it is normal that they ohm out around 130.

Did you also measure the resistance of the 2 resistors under the CPU of your factory repaired board?

 

[rayrayrayraydog]

Sure, here are the pictures. I have modified a C2750D4I rev 1.02, but also own a C2550D4I rev 1.03. That one had one of the resistors already there (first in group of three) and it measures 131.6 ohms (in-circuit), so my mods using 120ohm probably wont break anything. That signal is the TPM header pin 16: SERIRQ# and I have read somewhere a note that if it is unused, it should be pulled up (DS / errata / forum post).

The signal trace which the pullups around TPM are connected is same as the pin 9 (it is ugly on my pictures as it was soldered on mine from a previous LPCCLK only pullup, but I opted for recreation of the modification as pictured - you can of course use that pin from the tpm header and bend the wire around as necessary).

The wire looks thick, but its a piece of a wire from an old 80-pin PATA cable (25mil pitch ribbon), tinned before use. Also I need to clean this a bit, but I usually go to testing stuff before, as my flux is marked "no clean flux" and thus should not be electrically interfering.

Bumping this thread to say THANK YOU because my C2750D4I revision 1.03 has POSTed for the first time since I bought it off eBay. I had to install the 120ohm surface mount resistor rails on the bottom of the TPM header as well as another horizontally mounted 120 on the CPU side as as in the first pic. I did this with a very half-ass setup not suitable for surface mount devices but I figured what the hell -- it's this or the recyclers.

Before:


After:


I did notice two things -- one time while watching the BIOS screen showing sensors it hard locked with the BMC reporting 0v on Vcore, 1.0, and 1.1 again. I also see the bottom of the board near the TPM header getting quite hot, with a MB temp reported in the BIOS up to 59C -- is that normal?

Edit: My intermittent POST failures seem to be due to the voltage values on Vcore, 1.0, and 1.1 slowly dropping over time after I get into the BIOS screen. One some boots Vcore in particular will be around 1.2v and then I'll see later it has dipped down to 0.73v before a crash.

 

[ske4za]

I just wanted to update this thread to say SM is still repairing these. I just sent in an A1SRi-C2758 from a SYS-5018A-FTN4 that failed over a year ago that I was lazy and forgot about. They didn't need the whole system thankfully:

For this RMA Request, since it’s only the MBD that’s an issue for the C2000 and the system is out of warranty, I will be issuing the RMA only for the MBD.

I should have delivery tomorrow from the repair. I would offer to take any pics required but this has been well documented by now