• We’re currently investigating an issue related to the forum theme and styling that is impacting page layout and visual formatting. The problem has been identified, and we are actively working on a resolution. There is no impact to user data or functionality, this is strictly a front-end display issue. We’ll post an update once the fix has been deployed. Thanks for your patience while we get this sorted.

4GB RAM, BIOS only wants to see 2816MB

mikeymikec

mikeymikec

Lifer
Board: ASUS P5B-VM, latest release BIOS update
RAM: Crucial 2x 2GB DDR2-800 modules

I haven't installed Windows 7 yet, once I saw this anomaly I didn't much see the point until I've got possibilities like faulty RAM out of the way.

The processor is a Pentium D 935 (64-bit capable).

Memtest86+ v5.01 can see the two memory modules and their correct sizes in the SPD information section, but it is only testing 2815MB (currently doing the first pass).

The BIOS has settings for the onboard VGA with a default setting of 256MB reserved which I've since changed to 128MB (the system has a graphics card anyway), but it hasn't changed the overall memory figure.
 
After googling for a bit and finding tips about memory holes as well as modifying the DDR2 speed, I played around for a bit and a setting in the BIOS labelled 'memory remap feature', which has the following explanation:

ENABLE: Allow remapping of overlapped PCI memory above the total physical memory.

It was disabled, I've now enabled it. Altering the DDR2 speed made no difference.

I now have 4032MB available, which is good enough for me, but I am not sure of the implications of the feature I've just enabled.
 
Last edited:
mikeymikec said:
After googling for a bit and finding tips about memory holes as well as modifying the DDR2 speed, I played around for a bit and a setting in the BIOS labelled 'memory remap feature', which has the following explanation:

ENABLE: Allow remapping of overlapped PCI memory above the total physical memory.

It was disabled, I've now enabled it. Altering the DDR2 speed made no difference.

I now have 4032MB available, which is good enough for me, but I am not sure of the implications of the feature I've just enabled.
Click to expand...

Since the PCI address space is 32-bit, PCI (or compatible) hardware needs to be mapped into the lower than 4GB physical address space. What memory remapping does, is take the RAM, and fills the lower half of the 4GB address space with RAM, fills the upper half of the 4GB address space with hardware I/O ranges, and then fills in above that with the rest of the RAM.

(lower half of RAM)
(hardware I/O)
(---4GB boundry---)
(upper half of RAM)
 
You say you have not yet installed Win 7. So you have a choice to make. If you want to use the 32-bit version of Win 7, you will have to un-do the BIOS change you made. With 32-bit Win 7, the vid card memory addresses MUST be below the 4 GB limit. It appears your vid card has 1 GB RAM on it. You did not specify, but is that right? Allowing for 1024 MB on the vid card plus 128 MB reserved for the mobo vid card's use would get you close to the RAM size you are seeing. By the way, IF this is the route you are going, why have any RAM reserved for the mobo's vid chip that you are not using?

On the other hand, you can leave the BIOS setting as you now have it - remapping the vid card's addresses to above 4GB. Then you MUST install the 64-bit version of Win 7, because it can address lots of space over 4 GB. Then all your RAM will be available, except perhaps 400 MB for the OS and its reserved space. I don't know what you have, but the Win 7 package I bought had BOTH 32-bit and 64-bit versions in it.
 
You must log in or register to reply here.

TRENDING THREADS

Back
Top