ram underclocked

p4 2.53 133mhz at 150mhz with ddr400 ram on 5/4 divider giving 187mhz.
mobo asrock with i865G.
i built this around a spare cpu i had and its underclocked but fast enough running at 2.84.

my question is about the ram timings...its crucial ballistix claimed at 2-2-2-8 at 200mhz but it picks up by auto in bios as 2.5-4-4-8...i have manually set it to the faster timings but got the occasional crash in games,and then the bios would reset on startup to defaults again.

am i expecting too much of this ram? does underclocking affect the timing specs?

Using lower ratios often alters some timings that you do not see with most boards.

You may also need to give the memory more voltage. Ballistix is often rated for 2.8v while DDR default is 2.5-2.6v.