Need some skoolin'

I have a GA-P35-DS4 mobo with 4 gig of DDR2-1066 RAM.

When I set it on stock speeds - 9x266 (cpu) and 4x266 (ram), the memory's SPD comes up as being 1066. But if I try to set the core frequency to something higher (have tried 300 and up), it reports the the spd as 800.

What is this about? The board has 2 strapping frequencies for a 4x multiplier - 800 and 1066. I assume that at 4x266, its using the 800 strapping. If so, then the reported spd can't have anything to do with that.

Plus, if I do set a higher core frequency, I do get better throughput according to memtest - almost 5gbps. BUT . . . in every case, the machine with spontaneously reboot. So you would think that the problem is either instability with the cpu or the memory. But in almost every case, the cpu is solid. And for the couple of cases I've tested with memtest, the memory seems stable too.

For reference, at any setting other than stock, I've set the cpu voltage to 1.375 and the ddr2 voltage to +.3 (=2.24 - or so I've read). The ram - Wintec - is rated for 2.2 volts. In most cases I've left the other setting alone although in a couple cases, when I tried to increase FSB or MCH by between .1 and .2, it seems to have aggravated the instability.

I posted a simlar question a couple days ago but only got one response. I would really appreciate the help.

Thanks.

The SPD is essentially a table of timings for various stock speeds that the memory can do. If you use something other than the stock ones (800 or 1066) then it'll revert to the slower timings, if you haven't set the timings to manual.

Thanks for the info about SPD (serial presence detect). I'm still not sure why it reports spd paramaters for ddr2-800 when the timings are set manually - I guess it must just default to whatever is the first setting recorded on the chips.

Anyway, I've continued playing with the voltages. I've got the core speed up to 355 and 3x multiplier on memory (9x on cpu). I've bumped fsb voltage to .2 and MCH to .2 or so and it seems more stable. Still getting spontaneous reboots and some sluggishness that doesn't appear related to disk activity or anything else I can see.

I guess I'll just keep raising these until it's stable. However for this board supposedly you don't need +.2 on fsb or mch until you get to a core speed of over 400mhz. Plus, as I've already mentioned, I had been running it at 3.2ghz and stock voltages (except cpu) and timings for a few weeks with only sporadic problems. It seems very strange that it could handle the stress for so long and then just crack when I tried to push it up to 3.4 ghz.

Anyway, any comments, suggestions, etc are appreciated.