Old server mobo ram issues (win7 64 bit)

[yz250il]

Hello,
I have a Tyan s2877 mobo with 4x 1GB DDR-400 sticks installed.
the BIOS shows 4096MB of ram but windows 7 (64bit) shows only 3GB.

The max memory is unchecked.
CPUz shows the whole 4096MB, as can be seen in the screenshot

Any thoughts why?

 

[nevertryforme]

1] Click Start, type msconfig in the Search programs and files box, and then click msconfig in the Programs list.

2] In the System Configuration window, click Advanced options on the Boot tab.

3] Click to clear the Maximum memory check box, and then click OK.

4] Restart the computer.

 

[yz250il]

the maximum memory check box is not checked....