my mainboard is ami model 945P-A how much maximum ram support to my main board?

[dcranasinghe20]

my pc is win 7 64 bit so I installed 6gb ram to my pc but it shows as 3.37GB as usable. i need to use 6Gb ram.

 

[Calvin7]

945P chipset maximum memory is 4GB.

If you installed total 4GB memory, the system will detect less than 4GB of total memory because of address space allocation for other critical functions, such as:

- System BIOS (including motherboard, add-on cards, etc..)
- Motherboards resources
- Memory mapped I/O
- configuration for AGP/PCI-Ex/PCI
- Other memory allocations for PCI devices

Different onboard devices and different add-on cards (devices) will result of different total memory size.
e.g. more PCI cards installed will require more memory resources, resulting of less memory free for other uses.

 

[lordmogul]

You have indeed reached the maximum amount that chipset supports.
I have a board using the 945G myself and can confirm that it is limited to ~3.37 GB usable memory, even when you have installed more and all the memory is shown in the BIOS.

For being able to use more memory you might swithch to one of the following chipsets:
Up to 8 GB: 955X, 975X, P965, G965, Q965, P35, G33, G35, Q33, Q35, G41
Up to 16 GB: X38, X48, P43, P45, G41, G43, G45, B43, Q43, Q45

Note that to use more than 4GB DDR2 you want to get a board with 4 DIMM slots, since the biggest RAM modules supportet on intels platform have 2 GB each (which would be either 3x 2 GB, or 2x 2 GB + 2x 1 GB to get 6 GB total, or just going with 4x 2 GB for 8 GB in total)

Of coure it also depends on the support for your CPU. Of it's a Pentium 4/D you are limited to the 900 and 30 series and if it's a 45 nm Core 2 you are limited to the 30 and 40 series chipsets.
65 nm Core 2 are support on all 3 lineups.

But honestly you might be better of with just building a new system.