Card RAM vs Machine RAM?

markg2 · 16 Jul 2011

In another just resolved thread I increased the machine RAM from 2-->4GB on a Thinkpad T61 with Win7 32 bit.

I was advised in advance that the 32 bit (vs 64) would take a large overhead hit out of the memory. Further that the size of the video RAM would have a direct impact on the degree of the hit.

The machine has the Intel video combined versus a separate system and that RAM according to a diagnostic is ~367Mb.

My resulting total machine RAM is now 3062 per Task Manager.

2 points of clarification:

1. Why would the video RAM subtract from Machine RAM? It's my understanding that video RAM means RAM on the video card/processor that is separate from machine RAM and is so for the purpose of not interfering with one's installed machine RAM?

2. Plus, comments in the previous thread were indicating that with a video RAM of ~500Mb one would be left with ~3.2GB of machine RAM (32 bit OS) and yet I have less video RAM and less total RAM?

I'm delighted with my performance increase and should have increased the RAM far sooner. I'm simply needing a better understanding of this process going forward.

Mark

Wishmaster · 16 Jul 2011

Video RAM (aka VRAM) is indeed memory, and is seperate from the System RAM.
It doesn't actually take away from your system RAM though.

In a nutshell it basically works like this:

A 32bit Operating System has 4GB of addressable space.

This 4GB of space is all it has to work with. So it must map out your hardware into that allocated space.
Biggest things are the System RAM, and Video VRAM. Theres also a bit of overhead for the system itself though.

---So lets say you have a dedicated graphics card that has 1GB VRAM, and you install 4GB of system RAM.
The 32bit OS can only address a total of 4GB.
So in order to use the Video Card, it must assign its 1GB of VRAM to that adress space.
Now theres only 3GB of address space left. So even though you have 4GB of system RAM installed, it can not adreess it all, and therefore can only map out 3GB of it.

So its:
Video Card - 1GB space
System 3Gb addressed (of 4GB)
Total 4GB address Space

A 64bit OS has a much larger address space, and does not suffer from these issues.
So a 64bit OS would address it as:
System RAM = 4GB space
Video Card 1GB Space
Total 5GB address space.

However, Onboard or Integrated graphics, need to use memory as well.
Since they do not have thier own dedicated VRAM, the must "borrow" or dedicate a portion of the system RAM to graphics.
So in this case, you would see total useable system RAM as total - amount dedicated to integrated graphics.
Integrated does take from your system RAM.

whs · 16 Jul 2011

Open Resource Monitor > Memory tab. There you will see what is Hardware reserved (the first grey area on the colored bar).

All memory in the system needs address space. And this is being deducted from the 4GB which is the maximum in 32bit.

This will give you more details: http://www.vistaclues.com/reader-que...windows-vista/

markg2 · 16 Jul 2011

Thanks for the explanation. However, based upon it my current RAM math doesn't work.

Task manager says I've got 3062 total memory.

I've attached a screen shot from System Information for Windows showing the video memory. I do not know why it's showing two separate video adapters and have to believe that there's only one since it's the Intel integrated.

Just doesn't look right?