I recently bought one of these boards. It came from an IBM PC Server 320. Strangely I cannot seem to get the L2 cache going.
In the BIOS the L2 cache is "enabled", and there are no cache related errors on startup. When I run cachechk and speedsys, it seems the L2 cache is not enabled.
I suspected because this board has a Neptune chipset with slow asynchronous cache that maybe the L2 is not much faster than the main memory and the benchmark utilities can't detect it. However, enabling/disabling the cache in the BIOS has zero effect on benchmark results.
The board has a jumper for a turbo switch. It came with a jumper cap installed. Some systems enable/disable the cache when the turbo switch is toggled, but that does not seem to be the case here. In fact, it seems the switch does absolutely nothing. At least, I was not able to detect any change in system performance.
Then I ran CTCHIP34, which has a CFG for the Neptune. It does not allow me to change the chipset resisters. They seem to be locked. But if the register information it is reporting is correct, then it seems L2 really is disabled.
I suspected a BIOS problem, so I updated to one of the final versions, but it made no difference.
Hardware wise, the only other thing I can think to change is the Dallas RTC which is basically dead and throws up an error. Does the BIOS turn off L2 cache automatically if the Dallas chip is dead? I wouldn't think so, but who knows. I ordered a new one for good measure, but it hasn't arrived yet. I also double checked all the jumpers on the board, and they seem to be in order.

Does anyone own an M54Pe that can confirm that their L2 cache is working?