So what exactly is the deal with the imac video card...

[danstrife]

Hi everyone.

I purchased a 27" imac. I decided to try and play some games on them, so I installed windows 7.

Now, here's what boggled me. I bought the model that has an ATI Radeon 4670 with 256 MB Vram. I only noted that the ATI radeon 4670 available elsewhere only is available in 512 MB and 1 GB models. System profiler also said that my Vram was 256 MB, while I was running snow leopard.

I installed windows 7, and checked my computer to see if it could play some games. I noticed on this website http://cyri.systemrequirementslab.com/CYRI/ that it said my computer has 1.5 GB Vram, and a strange video card that is not a 4670. It's called a ATI display adapter (0x9488).

Then I ran my system check, and noticed another strange thing. My computer said that I have 1523 MB of total graphics memory, but this time, it gave the correct video card, an ATI Radeon 4670. If it helps anyone, it says that I have 256 MB dedicated graphics memory, 0 MB dedicated system memory, and 1267 MB shared system memory. That number isn't in any way related to RAM, is it?

Now I wasn't looking for quality gaming on my imac, but with 1.5 GB of Vram, it'd be a great possibility. However, unfortunately so, I imagine that this number is wrong from some reason. Could anyone shed light on this?

Thanks.

 

[Vylen]

VRAM is actually your system RAM being used put to use by Windows for your graphics card. It's something put in place since Vista to help people use the relatively more graphics intensive environment. The operating system uses a silly formula that sets a minimum RAM to be shared, but no maximum, and sometimes it does weird things like give you 1.5G VRAM (it's based on the cards dedicated RAM and your system RAM, the less dedicated RAM, the more VRAM).

 

[Sun Baked]

The card you have is...

Card name: ATI Mobility Radeon HD 4670
Manufacturer: ATI Technologies Inc.
Chip type: ATI display adapter (0x9488)

And even people with Dells are getting the same wrong VRAM on their card, probably a driver issue.

 

[TMRaven]

The 4670 in the iMac is a mobility card, so that's probably why it has less VRAM as the more popular desktop counterparts.

VRAM simply stands for Video Ram. I've not heard of windows allocating system ram to share with the dedicated video ram of a dedicated gpu, but I could be wrong-- the whole 1.5 thing is probably some type of error.

 

[Pachang]

It's def 256mb. Apple only put 256mb in the mob 4670 to save money I guess.
Most laptops with the 4670 have 512 or 1gb.

 

[Vylen]

The 4670 in the iMac is a mobility card, so that's probably why it has less VRAM as the more popular desktop counterparts.

VRAM simply stands for Video Ram. I've not heard of windows allocating system ram to share with the dedicated video ram of a dedicated gpu, but I could be wrong-- the whole 1.5 thing is probably some type of error.

Sorry, yes, VRAM is total video RAM. This is Dedicated Video RAM + Shared RAM from the system. It's handled by Windows.

Windows Vista introduced the WDDM - Windows Display Driver Model - and it's carried on to Windows 7.

Read about it here:
http://download.microsoft.com/download/9/c/5/9c5b2167-8017-4bae-9fde-d599bac8184a/GraphicsMemory.doc

It's one of the reasons why my laptop, with its 128MB of dedicated graphics RAM, has 1.4GB of total VRAM (an increase from 700-something MB after I installed more RAM).