Available memory is limited to 4g

I have a Asus M2N SLI motherboard , AMD X2 6400 processor , Dual channel memory kit 4g in first bays, matched dual channel 2g in second bay all modules are OCZ  ddr2 800mhz pc2 6400, 2 SLI enabled Nvidia 7300GT graphis cards, Award BIOS ver901.

the bios states max memory at 4g . the unit will not boot if the dual channel sets are installed correct. BIOS states 6g installed 4g available.

I am running win xp 64 is there a setting for extended memory, or is this in the bios, there is no setting in bios to address this.Any suggestions would be gratly appreciated . Have been at this for quite some time. Asus support is not too helpful

It might be worth checking out if your board has updated firmware - if not, and support is being crappy, you should look at upgrading your board. ASUS in my experience has not been stellar - I can't even find straightforward ratings on what your board will literally support in terms of RAM. I'd imagine since it is a relatively recent board  you ought to have at least 8GB or more supported. Most AM2+ boards have that.

Windows XP 64-bit does not have a memory cap at 4GB, but rather at 128GB. So there is no need to de-limit anything. Are you 100% sure you are running a 64-bit version of windows? It's a silly question, but I'm just trying to cover all the bases I can readily think of.

Nelson

While your looking stuff up; are you using any aggressive timings at all?

Andrew