The PC configuration had been upgraded to add two 1 GB memory sticks. The new memory had faster timings than the original two 256 MB memory sticks. The PC adjusted the speeds to match the older, slower memory chips.
Memory overview. Note the speed is 199.5 MHz and FSB:DRAM is 1:1. Also note the clock numbers.
Four sets of memory:
I removed the two original memory chips, and the memory speed is about 1/3 faster at 266 MHz and with faster clocks.