wathman :
The 512MB video card thing is true if you are talking about an integrated graphics card, or one that uses shared memory. Most discrete desktop graphics card have their own onboard memory, and do not share with the system's available memory resources.
Right but wrong. The issue in 32-bit OS's is that, irrespective of whether the RAM is on the video card or just main board RAM devoted to video tasks, it still is accessed by memory address. A 32-bit system can use addresses only up to 4 GB no matter where they are. When a video card has its own RAM, what happens is the system sets a small pointer so that any attempts to access a specified range of RAM are re-directed to the video card, rather than the mainboard RAM.
Suppose you're a mail deliverer in a weird post office system that uses stickers on each package allowing house numbers up to 4 characters long. And that's ALL the address info you get, because there is only one street in town. You have no problem on 1st Avenue with the first 9,999 houses. But the people on that street with house numbers of 10,000 or higher will never get any mail because the addresses that high cannot be written on the envelope. By decree all artists live in house numbers from 8,000 to 9,999 and they get their mail that way. Everyone else has to live in house numbers from 0 to 7,999. This is using mainboard RAM. Wisely, town council is not hiring any contractors to build new houses beyond 9,999 on 1st Avenue.
Now along comes a developer who creates a new small 2nd Avenue out at the end f town with houses only from 8,000 to 9,999. He also changes the roads so that there's a permanent detour after 7,999 from 1st Avenue over to 2nd. Then they decree all the artists will live over on 2nd Avenue in the new houses. You still have no problem delivering their mail, but you can never get to the high end of 1st Avenue. That's OK, because nobody is living there, anyway. This is the model with dedicated RAM on the video card. But note that this upgrade for the artists does not free up any extra housing space for the rest of the people, because the end of 1st Avenue is unreachable.
But you move to a smaller town in which the builders have only made houses up to the 4,999 place and there still is no 2nd Avenue yet. Similar to the first town, here artists all live in numbers form 3,000 to 4,999, and there are only 2,999 places for other people to live. Your only minor issue is somebody has to be sure nobody tries to send a letter to house numbers from 5,000 to 9,999 because there are none - only empty lots! This town has unpopulated RAM slots on its motherboard.
Next comes that enterprising developer friend of the artists and builds that 2nd Avenue piece and the road detour. Nobody cares about the fact that the end of 1st Avenue is inaccessible, because there are no houses built out there anyway. You still have no problem delivering mail. Sure, the guy back in the main post office who checks the addresses now has to revise his rules so that only addresses from 5,000 to 7,999 are prohibited. However, moving those artists from their original locations to a new ones at 8,000 to 9,999 2nd Avenue has freed up all the houses numbered 3,000 to 4,999 on the part of 1st Avenue that still can be accessed, so the town can now accommodate more workers living there. It is more productive!
Along comes a second developer, VERY stubborn, who offers to build houses on ALL the vacant lots on the far half of 1st Avenue. Town council says why do that? Nobody can get to the end of the street beyond 7,999! The developer says "Not my problem, baby! That's my offer!" So town council has to decide whether to have those 5,000 houses built so that only 3,000 of them actually will be available for new workers. Whatever happens, you as the mail deliverer still have no trouble doing your job.
Meanwhile in the background the rumors are circulating that there's a really BIG town over to the west that makes all their mailing labels with 8 characters, not 4!
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