8KNXP - Corsair Twinx 3700 - Bios F8

Hi,

I have 1024mb Corsair Twinx 3700 (2 x 512mb) installed on my 8KNXP.

When I received the mainboard it had F3 bios installed, and simply
didn't recognise the memory at all. After reading some posts here, I
installed F6a(beta) and changed some of the timings and it finally
recognised the memory and ran at dual rate although at much reduced
speed.

Finally I have recently installed F8 (again after reading posts here)
and I was looking forward to the bios finally recognising the 3700
memory...but alas after running CPU-Z it shows the memory as 3200
rather than 3700 and therefore again not using the speed that I paid
for.

So my questions :

1. How do I get the 8KNXP to recognise Corsair Twinx 3700 memory?
2. Does it need to recognise it to make use of the extra available
speed?
3. Is it just CPU-Z that is not recognising the 3700?
4. Is there another way of determining whether the 8KNXP is actually
recognising the 3700?

Any help with this setup would be appreciated.

Spec :

P4C2.8 running at 3.5
FSB 985
mem : 2.5-3-3-8 running at 5:4
OS : Windows XP sp1
fx5900 128mb

Thanks.

Matt. Davies