I have a Dell OptiPlex 755 USFF which has an Atmel AT26DF321 SPI flash
chip (which is like an AT25DF321 and has the same device ID except it
doesn't have a HOLD# pin). I've used flashrom to read and write the
same chip on another board by ISP using a BeagleBone Black, 10-cm jumper
cables, a SOIC clip, and an ATX PSU.
However, flashrom with the same ISP setup fails to probe the chip on the
OptiPlex. I've tried two different known-working BBBs, different
cables, two different Pomona SOIC clips, connecting WP# to 3.3 V,
connecting what would be HOLD# on the AT25 to 3.3 V, and different
spispeed clock frequencies from 1 kHz to 10 MHz.
I've tried powering the chip (and the rest of the board's 3.3-V rail)
with a 3.3-V line of the ATX PSU, and I've tried instead powering the
whole board with the computer's 12-V PSU. I've also tried running
flashrom while holding down the power button to keep the system in
reset. Following some advice on <http://flashrom.org/ISP> I even tried
removing the DIMMs and CPU.
Every time I get only bytes of 0xff from the chip, as in the attached
log. In my experience that usually means either the programmer isn't
properly connected to the chip or the programmer uses a different data
voltage than the chip does. But I've checked and rechecked all of the
connections, and I know both the BBB and the AT26DF321 use 3.3-V data
Unfortunately there don't seem to be any schematics available for this
board (Dell model number 0HX555, ODM model number HX533 A00, ODM might
be Asustek or MiTAC). This system does have an Intel Management Engine
in the northbridge, but even if that was running I should at least be
able to probe the chip and read its contents.
Does anyone have any ideas of anything else I could try (short of
desoldering the chip from the board) or about what the problem may be?
Patrick "P. J." McDermott
Lead Developer, ProteanOS