User:Jdstroy/clipboard

Missing memory
Hello,

I've asked this question before, but it was archived before I got back to responding to the request for more information. :) (Missing Memory, WP:Reference Desk Archive/Computing/2006 August 7th)

Recently, I've seen several computers (of two friends) with a certain amount of physical memory, yet, when the physical memory is examined in the operating system statistics, it shows up as slightly less.

The reported amount can be retrieved through the "System Properties" Control Panel applet, the "DirectX Diagnostics Tool," and the Performance tab on "Windows Task Manager" (under the heading Physical Memory, Total).

The first and second computers (index 1 and 2 respectively) are produced by HP/Compaq (the first is branded HP, and the second is branded Compaq, purchased after HP's acquisition of Compaq). The third computer is manufactured by Gateway (a 7330GZ, if I remember correctly).

I've had people tell me that the missing memory is reserved by the graphics adapter through Unified Memory Architecture (UMA) / Shared Memory. However, I do not believe that it explains this case, as you will see that the second and third computers listed have video graphics memory sizes that are not the same as the missing memory. For the first computer, it's believable. For the latter two computers, however, it wouldn't seem reasonable to have a half and a fourth of the graphics memory implemented in system memory. It would be more reasonable to design the graphics adapter to use an all-or-nothing approach with shared memory.

All of the graphics adapters are built-in, onboard video. (The last one is a laptop.)

The second machine is new (just purchased), and has never been used; malicious third-party software is out of the question.

No, I'm not looking at "free memory," I'm looking at "Total Physical Memory."


 * DMA doesn't play a significant role in this question; not to my knowledge, anyways
 * Windows shows even the memory allocated to itself.
 * There is currently only one graphics adapter per machine.

Any thoughts?

Jdstroy 05:10, 13 August 2006 (UTC)