The additional costs of a board with half a GiB of memory
Double the memory on a graphics board and, depending on what segment that board sits in, you can almost double the cost. That doesn't bode well for 512MiB boards appearing everywhere you look! There's also a knock-on set of costs associated with doubling the memory size, depending on whether you're doing it with more DRAM devices or not. If you're increasing the number of memory chips on the board, there's an electrical and power cost to be paid. The added devices need power and they give off heat. That can then translate into more cost spent on cooling, along with the power infrastructure on the PCB to provide the electrical supply. If you're going to do it with 16 memory chips, that's also a doubling in board space needed for them, potentially increasing the size of the PCB.However, recent advances in memory technology have seen memory densities double, allowing you to put 512MiB on a board with the same amount of DRAMs. A 512Mibit device, of which GDDR3 samples are shipping from Samsung as I type this, allows you to get 512MiB on a board with no more than eight DRAM devices. There's still an associated extra cost in terms of making sure any existing power circuitry is up to the job, but that's marginal.
Performance costs and considerations
As we've seen time and time again with low-end boards that pack the memory on, but which use asthmatic memory bus widths to talk to it, there's little point in giving a bandwidth-starved graphics chip more memory which it can't realistically use to accelerate 3D performance. Here, on-card caching schemes work best to make the most of what they've got, especially if you want to use the board for something other than 3D graphics and games. While you might not have the bandwidth on the board to feed the GPU very well (often less than 5GiB/sec on 64-bit memory bus low-end hardware) to render complex scenes, that doesn't mean you have to leave blocks of memory empty. You still want to upload data to the board even if it won't be processed for a few frames. Speculative preloading on 512MiB low-end hardware would make some sense, if the driver is able.However, the almost overriding factor for low-end hardware is its inability to do much with huge on-card framebuffers. With the rise of PCI Express, here's hoping that extra costs to low-end hardware aren't seen in the push to give the masses a fatter framebuffer, and schemes like HyperMemory and TurboCache are used instead. There's currently a serious false economy to purchasing a large memory low-end board, and that's not going to get any better without investment in driver advancement by the IHVs with 512MiB (or indeed 256MiB) boards.
That said, there are immediate detectable benefits for games, when using a 512MiB board, especially if they don't quite exert memory pressure on a 256MiB board all the time, but do so every now and again. Slight overflows in card memory due to memory pressure, causing the board to go out to system memory with data, are manifest as framerate hitches, pausing gameplay for a short length of time. With a larger memory space, that hitching can be lessened, resulting in a higher low framerate, slightly higher average frames per second and an smoother overall game experience. For many gamers that will be the primary benefit, over any ability to increase resolution or image quality!
Surely all that extra memory lets you use higher resolutions in your games, or more AA at the same resolution?
Of course. One of the things more than 256MiB of memory will bless a fairly high-end board at the moment is the possible ability, especially if you're on the cusp of being shader limited, to bump up the resolution of your game and keep pretty much the same settings and framerate. Or bump up your AA level at the same resolution. However, and this is a huge however, who realistically has the display capable of doing much more than the 1600x1200 that current high-end hardware is happiest with? I myself used to have a CRT that'd cope with greater resolutions, but it neither had the screen real-estate or image quality at higher-than-1600x1200 resolutions to make me want to do so.With the large scale adoption of the LCD monitor for the modern PC that'll take a current high-end board, that a 512MiB memory size is most suited to, you're realistically limited to a 1600x1200 or 1680x1050 LCD panel, unless your display budget runs into the thousands, rather than the hundreds that most can spend.
So there's the option to crank things up higher in terms of resolution, but market forces dictate that if developers are to take advantage of 512MiB hardware, it's going to be with increased quality of basic art assets in the game title, with increased usage of memory-intensive graphics algorithms, that we'll see, rather than any optimisation for higher resolutions.
That leaves you, without many games doing it for you, to force memory pressure yourself, to see benefits. Bumping AA (if you even can) at high resolution is the easiest way to do so. Jacking up in-game settings to maximum is another way, if you're not there already with a current high-end board.
Summary
Should the purchase of a 512MiB board attract you, be very aware of the physical, electrical and environmental (heat, mainly) issues associated with such hardware. Boards may be bigger, hotter and require larger power supplies, depending on the GPU and the DRAM devices used.Secondly, there's a monetary cost. More memory costs more money. I'm hoping that's a given. Thirdly, beware of the false economy in buying a low-end board with such a framebuffer size. It's not really sensible with current low-end hardware (256MiB GeForce FX 5200 anyone?) and with twice that memory size, it's even less economical to do it with a 512MiB board, given increased costs.
Thirdly, be sure to consider your display(s), should you be seriously considering a high-end 512MiB board. Lastly, be sure of the benefits you're going to get, whether that means forcing them or otherwise.
That leaves half-GiB hardware as something to seriously ponder, rather than jump on as soon as it appears. That should be the case at the moment, already, for the clued-up HEXUS reader, but just incase you've been sleeping at the back all this time while we attempt to clue you in on what's hot and what's not, be sure of why you're choosing a 512MiB board over the alternative.
So with all that said, would you like a peek at some 512MiB high-end 3D hardware? Ah, go on then.
