Having trouble getting a good read from a Macronix MX25L3206E in situ Thinkpad E420 Sandy Bridge/Cougar Point PCH. Don't believe it's a programmer problem because I used the same programmer and pinouts to successfully flash a Winbond W25Q32.V in a different system.
I found the Wistron LLW-1/LGG-1 schematic and matched the flash chip up with the silk-screened label. Tried it in system with system power. I've pulled the board and RAM. Also tried removing CPU. Symptoms of the problem are:
- On system power, doesn't detect chip. - Using an external PS, when I restrict the current to the point there's a vdroop to ~3.0v-3.2v, flashrom detects the chip. If I give it more current (at 3.3v), the chip disappears and flashrom no longer sees it. - Occasionally it acts like a successful read, WRSR updates correctly but resulting file is mostly FF with a section of pages of 00 and some with alternating bit patterns. Oddly, the file is consistent over multiple runs and diff reports no differences, but there is nothing in it that looks like actual data and ifdtool says there's no descriptor.
Suspect the issue is as described on https://www.flashrom.org/ISP- that ME is getting powered and locking/hiding the chip. It suggests connecting the reset line to CS. Searching the schematic for RST results in numerous pages. How can I identify the right place to accomplish this, preferably without soldering?
Alternatively, I see in the SPI programming guide there might be a couple other ways to disable ME?
1. Temporarily disable the Intel® ME through the MEBX. Power off or cold reset. - This option is only applicable to non-Intel ME Ignition firmware. 2. HDA_SDO(Manufacturing mode jumper or Flash descriptor override jumper) asserted HIGH on the rising edge of PWROK. Power off or cold reset. Note: this is only valid as long as you do not specifically set the variable Flash Descriptor Overrride Pin-Strap Ignore in the Flash Image Tool to false.
I found #2 on the schematic with a not installed resistor (what does "DY" stand for anyways, "Damn You"?) but can't find the label for it on the motherboard and it looked like it would also need soldering beyond my capability.