Video RAM - how much do you really need?
Contents1. Introduction & Ram Technology2. What video RAM gets used for 3. Video RAM usage in Oblivion 4. Video RAM usage in S.T.A.L.K.E.R. 5. Video RAM usage in BioShock 6. Video RAM usage in Sega Rally (Revo) 7. World in Conflict, Call of Duty 4 and Crysis 8. Final Thoughts & Suggestions The first 3D accelerator add-in boards (merely called graphics cards today) appeared on the market over ten years ago and whilst the processing power and raw capabilities of the main chip have increased beyond all expectations, the amount of memory on the circuit board has increased rather more slowly. However, the latest games are becoming ever more demanding on the resources a PC has to offer. So if you're out to buy a new graphics card, what do you do - buy the one with the most memory, the fastest memory, the latest memory type? We delve into the mysteries of video RAM and take a brief look at the different types and what it gets used for, before we examine just how much your graphics card really needs. But first though: a history lesson.... hey! Come back! Once upon a time, in the dark ages of PC games, graphics were nothing more than a few lines, dots and text splattered around the screen. They were flat, bland and nothing like reality; we didn't care though, we had imagination to fill in the gaps! Then somebody had the idea of taking those lines and dots, and arranging them in such a way that it looked 3D, even though it wasn't. Our brains had become so used to making the wild jump from blocky graphics to reality, that this was an absolute revelation. Graphics in PC games had become the new crystal meth and we couldn't get enough of them. Technology wizards around the world seized the moment and produced the first 3D accelerators: independent processors that would do all of the complex calculations needed in rasterisation, a process whereby shapes in a 3D world are converted into a grid of pixels, which are then coloured to produce the final image. General CPUs could do this but sometimes quite slowly, so having dedicated hardware to handle the job, along with some other tasks, made a lot of sense. But these processing chips needed to have some memory close to hand, that could store important data and the final image - thus graphics cards came with their own onboard RAM. Types of RAM for graphics cards This chunky SDRAM fella could hold 2MB of data and ran at a, for the late 90s, blistering 140MHz. Over the years, graphics cards for desktop PCs have sported a whole range of different types of memory, but they all share on thing in common: they were designed for raw performance in 3D rendering. They've all been based on DRAM (dynamic random access memory) but with various changes and updates along the way; one of the earliest types to be used was called Video RAM, oddly enough. It's card-up-the-sleeve trick over normal DRAM was that it could be accessed twice at the same time, allowing the processing chip to use the memory whilst the display part of the card was getting an image. After that, cards sported versions such as Fast Page Mode DRAM, WRAM, EDO DRAM, SDRAM and SGRAM. All packed with tweaks to ensure that the contents can be read, copied, moved, etc as quickly as possible. One of the biggest changes came at the end of the last millennium: DDR SDRAM or Double Date Rate SDRAM. The accessing of memory chips is synchronised by a central timing voltage, that bounces between two levels at a set rate; every process is timed to this "clock". DDR SDRAM chips do all of their work timed to when the clock voltage changes and not when it's "on" or "off". This means for every tick of the main clock, the memory chips are doing two things: thus the rate at which the memory can be read or written to is doubled.
DDR SDRAM has gone through even more technological updates (we're currently on version trois, with DDR3) but along the way, GDDR has popped its head up. Without going into the long and convoluted reasons, this stuff isn't quite the same as the equivalent named DDR (for example, GDDR2 is more like DDR than DDR2, and there's now GDDR4) but it doesn't really matter. All that counts is that the latest video memory technology allows the chips to run faster, cooler and transfer and store more data. So is speed everything? For graphics cards and 3D games, the answer is no.
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