Asus P5KC - Manual (Page 41)

ASUS P5KC 2-17
• Some old-version DDR2-800 DIMMs may not match Intel ® ’s
On-Die-Termination (ODT) requirement and will automatically downgrade
to run at DDR2-667. If this happens, contact your memory vendor to check
the ODT value.
• Due to chipset limitation, DDR2-800 with CL=4 will be downgraded to run
at DDR2-667 by default setting. If you want to operate with lower latency,
adjust the memory timing manually.
For DDR3 DIMMs:
• If you install two 2 GB memory modules, the system may detect less than
3 GB of total memory because of address space allocation for other critical
functions. This limitation applies to Windows Vista 32-bit/Windows XP 32-bit
version operating system since it does not support PAE (Physical Address
Extention) mode.
• If you install Windows Vista 32-bit/Windows XP 32-bit version operating
system, we recommend that you install less than 3GB of total memory.