Graphics Memory Sizes Compared: How Much Is Enough?

EconolineCrush writes "Trying to decide between whether or not to get a 64MB graphics card, or spring for that 128MB version? Hit up this article, which explores the performance of ATI and NVIDIA-based cards with 64 and 128MB of memory, before swiping your credit card. Not so long ago 32MB was the top end for graphics memory on consumer video cards, but now even budget cards are available with 128MB. 128MB might seem excessive now, but a year from now 64MB cards might just be obsolete."

Comments

Getting an nvidia? 128 or 64? Read this...

[Rahga]

Here's something you should consider before buying a 128 MB GeForce Ti-series card. There are four choices you can make right now:

Ti-4600: Highest price, best features, 10.4 GB/s memory bandwidth, 650 MHz memory clock
Ti-4400: High price, excellent features, 8.8 GB/s memory bandwidth, 550 MHz memory clock
Ti-4200 (1): Decent price, great features, will handle BF1942 and UT2003, 64 MB limit, 8 GB/s memory bandwidth, 500 MHz Memory clock
Ti-4200 (2): High price, great features, slowest out of all 4 thanks to memory speeds, will handle BF1942 and UT2003, 128 MB limit, 7.1 GB/s memory bandwidth, 444 MHz memory clock.

Basicly, on the 4200's, if you go for double the memory for almost double the price, you will see a performance hit.

After my research (urged on by PNY's box), I decided that by the time I need 128 Mhz, I'll also want the features of a chip beyond the current Nvidia line.

Of course, if you want anything that performs beyond the 4200, then why bother reading anything here in slashdot? You're getting at least 128 MB on your card ;) .....

So, this weekend, I found a 64 MB Ti 4200 for $129, and it printed out a $30 rebate at the counter. Happy day, indeed. I spent the rest of the weekend playing OpenGL-boosted Doom and Hexen.

BTW, if you are completely out of the know, but love gaming, do not but the MX series of cards. They are not for you.

Re:64Meg Card obsolete?

[comic-not]

My words exactly! Somebody might be led to believe that the '89 Amiga 3000 sitting on my side table is somewhere way beyond obsolete but that's not true. All the programs run as well as they did, what, 13 years ago. If I need quick and dirty subtitles on a video or just fancy a quick game of pinball, everything is running 15 seconds from power-up. And my kids seem to prefer those classic games as well :-)

Comic-not

Re:removable RAM?

[John_Booty]

this might be offtopic, but why can't the RAM on graphics cards be modular, like the stuff we stick in computers?

Another reason in addition to the ones posted by other users... when are you going to upgrade the memory on your graphics card? Perhaps 12 months after you bought it? Two years?

--If you're going to stay close the cutting edge in PC graphics, you'd be buying a new card at the point. Considering the pace at which PC graphics card technology increases, your card would be fairly dated by that point anyway and you'd be looking at another one.

--If you were going to buy the extra video memory fairly soon after purchasing your card when it's still bleeding-edge, why not buy a card with that much RAM in the first place?

Of course, other posters have noted lots of good reasons as well such as the profits made by board/chip manufacturers on the extra RAM, physical RAM connection issues, etc, etc.

Re:What are you doing with it?

[The Real Chrisjc]

Gawd! Don't you read slashdot regularly?
You don't?
OOhh. .

http://slashdot.org/article.pl?sid=02/09/02/232121 1&tid=137

Chris :)

I'm not trying to brag or anything, but..

[kaoshin]

My 1MB trident SVGA card works just fine. Enlightenment looks great in 800x600x16bit,
and I play alpha centauri, starcraft, freeciv, etc. And I have been using it day and night since around 1993 without it melting, and with no noisy cooling fans. Considering it cost me one buck, I think that it is not a bad bargain.

Not just for gamers

[Anonymous Coward]

Anyone running Mac OS X 10.2 ('Jaguar') would be well advised to spring for the fattest card they can afford. The new compositing engine treats every window as an OpenGL texture, so the more RAM you have the more windows you can open before your graphics card starts pushing textures into main RAM. The performance difference between a 16Mb PowerBook and a 64Mb Power Mac is noticeable (and yes, I know there are other factors in play there :).

If other windowing systems head in the same direction (and MS indicate that Windows will, in a couple of years' time - X... who knows? Anyone have a plan there?), the advice will presumably apply equally.

It's mostly texture memory

[ikekrull]

These card use up to about 4MB - more like 2MB or less for 16-bit modes, for the framebuffer, and the rest is used solely for storing textures.

If you do not use OpenGL/Direct3D, then any RAM above, say 8MB (you may be doing dual or triple-head at 1600x1200 32bit or more), is completely useless.

The extra bandwith on the cards is also useless, as only 3D operations are accelerated across the super-fast busses built into these cards.

Everything else, including 2D blits in the majority of available OpenGL/Direct3D drivers are handled by the host CPU and involve reading from system RAM and passing that data across the AGP bus.

I am not aware of many (any?) games that can take advantage of more than 64MB of texture RAM, and while games that *may* take advantage of >64MB are on the horizon, the big news for games is vertex/pixel shaders, rather than the ability to texture map hundreds of megabytes of pixel data per frame.

There are applications that will benefit from the availablity of 128MB or more texture RAM, but these are typically custom-written scientific visualisation apps, or conceivably you could use 128MB of textures to do realtime previews in your lightwave/3DS Max/Maya/Blender scenes.

However, the actual utility of this RAM for most desktop users and even gamers is rather questionable. I don't doubt that the Radeon 9700 and the NVidia Ti4600 are fast cards, but they still rely heavily on the host CPU to achieve their stellar performance, as opposed to some of the professional cards which provide much more capable geometry engines and accelerate practically all of the openGL pipeline, as opposed to the consumer cards which are focussed mostly on texturing and fillrate optimization, ideal form games but not necessarily optimal for other forms of 3D activity.

That being said, the pace of development from Intel and AMD have made it more difficult to justify using dedicated hardware for these seteps, as a 2GHz Athlon will probably out-light-and-transform dedicated OpenGL hardware, which is much more costly and low-volume to produce.

The SGI O2 is a good axample of a machine that simply uses system memory to store textures, and while the SGI's graphics system is not in the same class as some of the more modern 3D boards from NVidia and 3DLabs, it is certainly sufficient to do impressive texture-mapping demos. This is really not an option on the current x86 architectures, but is a useful example of the 'other' way to handle texture memory, as it allows the user of the system to make maximum use of the resources available - i.e. when 3D graphics are not used, the 'texture memory' is available to the apps, and vice-versa.

I think it is amazing that we now have consumer cards that contain more texture memory than was typically available as system RAM in a mid-range 3D workstation a few years ago, but the unfortunate thing is that very, very few people are able to put those capabilities to real use with the current crop of system architectures, applications and games available

Doom 3

[Anonymous Coward]

According to Anandtech's review of the Radeon 9700 (http://www.anandtech.com/showdoc.html?i=1656&p=24 ), Doom 3 will require at least 80MB of graphics memory. Go get the 128MB card.

Re:removable RAM?

[Milican]

OK, well 2pF may not seem like alot and in most cases its not. However, what you are forgetting is the scale we are working at here. I tried to lookup the exact memory module for a GeForce card, but I couldn't so I just went to Micron's site and looked up their spec on their 256Mb DDR333 SDRAM. If you will look on page six you will see the capacitance ratings for each signal line are as low as 0.5pF for three of the signal lines and max out at 4.0pF for the I/O (data) lines on the memory module. So lets look at the 2pF number again. By adding a connector you increase your input capacitance by 400% in some cases and 50% in the best case scenario. This is very bad and will directly impact how much memory can be put on one bus and how fast the memory can be timed. The more input capacitance you have on a line the harder the output buffers of the graphics chip (or memory controller) have to work. More input capacitance directly affects how fast you can get that nice little square wave signal to look nice enough to be registered on the other side. The more input capacitance the longer it takes, and this is all very relevant at the speeds we are talking about here. Also, FYI other factors for not using a connector include trace length. By adding modules you are increasing trace length by a large amount (relatively speaking of course). This also adds input capacitance.

So now you are probably asking. How much capacitance can a typical graphics chip or processor drive? Well I tried to find the datasheet on nVidia's website for their GeForce chips, but didn't turn up a thing. So I went to Intel's site and looked up the datasheet for their 845G chipset with integrated graphics. If you look on page 525 you will see that the output drive for the Intel chip is 12pF. So now you can probably see the problem. Assuming all we drove were memory modules directly from the 845G (which we wouldn't in real life) we could put just two to three 256Mb (32MB) modules on board without connectors. If we put the Molex connector you specified in between that number changes from 1 - 2 chips. In real life we would put a nice buffer in between that has a stronger output drive in between the 845G and the memory. Like TI's 24-Bit to 48-Bit Registered Buffer. That sucker has a 30pF drive and each buffer could easily drive 6 - 7 modules for a total of 256MB of RAM without the connector. Add a connector and this number deindles to 4 - 5. Anyway, I'm sure you get the point. At this scale even a 2pF connector makes a big difference.

However, after saying all that I should mention that I do not believe that these electrical considerations are the main or only reason the cards are not expandable. I think alot of it has to do with demand. Very few people are gonna upgrade their video card with more memory. I don't know any Matrox Millenium owners, including me, that upgraded their memory on their video cards. Because the economies of scale for a specialized memory make them much more expensive to produce than consumers like myself are willing to pay. In adition, by the time I am gonna upgrade a cards memory I can probably buy a brand new one with that amount of memory for the price of the piddly module ;)

JOhn