Video RAM maxing out system what happens?

What would happen if I were to put a 512MB video card in an older computer that has a total maximum installable amount of 512MB RAM (with the 512 maximum installed).

Would the OS even be able to boot? If it did boot up would you just get some sort of Low Memory error? Assume Win7 as the OS.

Thank you!

Memory on your video card is totally separate from your system memory. The system maximum refers only to memory installed on your motherboard.

Assuming the card was otherwise compatible with the system, it would work fine.

except a machine that can only have 512mb of ram installed has little business running win7

That isn’t true. For example, the notable 4GB limit of 32-bit addressing includes both system memory and video memory.

Believe it or not it runs on even less than that. Here’s one of many videos on Youtube running 7 on old hardware.

For some reason I was under the impression your video memory, while on distinct chips apart from the system RAM, is counted in the maximum addressable memory. So that if you have 1Gb max memory and you are using 256Mb for video ram the system can then only address the remaining 768Mb for things other than video.

Can, and should are very different things :smiley:

The 512 MB limit probably comes from the RAM interface, and refers to how much RAM can be handled by the memory controller. Your typical 32 bit CPU can address up to 4 GB of RAM. However, if the memory controller can only handle up to 512 MB, then you can only put 512 MB worth of memory sticks into the computer.

While the memory controller may be maxed out, the PCI bus (or whatever bus type your video card uses) doesn’t rely on the motherboard’s memory controller, and can map memory into the system that is outside the bounds of your memory sticks. So your system, even though it can only access 512 MB of RAM in memory sticks, can also access the video card’s additional 512 MB as well.

What the system probably has is a 512 MB limit on memory sticks, and a total memory limit (including all PCI devices) of 4 GB. The BIOS ROM and devices built into the motherboard will take up some of that space.

Yes and no. It is separate in that video RAM is used for the graphics card, and nothing else. It isn’t separate in that the video RAM has to be mapped into the system’s memory address space. This is because devices use “memory-mapped I/O.” Simplified, it means that the device claims a range (or ranges) of system memory addresses, and any data written to and read from those specific memory addresses are actually going to (or coming from) the device. So in reality, all 512 MB of video RAM is also taking up 512 MB worth of addresses in system RAM. Now, since the system’s address space is 4 GB and the actual physical system RAM is only 512, it’s highly unlikely that the card’s video RAM is actually occupying much system RAM (it’s likely to be abstracted away by virtual memory.)

most likely, yes. it’ll be fine for a bit 'cos even with Aero enabled, regular desktop usage should only take up less than 100 MB of video RAM. If you fire up a 3D game with lots of textures, though, well, you get what you deserve :wink:

Thank you. I couldn’t figure out how to search for the answer on Google. I always like reading your posts regarding computer science. This was the unambiguous answer I was looking for.

Clarity is such a rare gift in tech answers. Thank you!