Simple Question: How much memory on board?

[Dr. Ffreeze]

Hello All,

I was thinking about getting a new video card sometime in the next few months. I run across some 'uncommon' boards like the GeForce 6800 GT 128MB and I begin to wonder.

How much on board memory do I need for each resolution, AA, and AF combo? What would a good formula be?

(Height in pixels) x (Width in pixels) x (bit depth) = starting point

Older style super sampling (if I understand correctly) was easier but how much extra memory does the newer types of AA use? Heck does AF use any extra on board memory?

After that is done, what are some basic loads that game textures occupy for say, DirectX 6, 7, 8, 9, and Very High 9?

With all this, I might be able to make a simple baseline chart that has the minimum resolution/AA/AF that a given video card should be able to handle with no texture thrashing out to main memory.

Thank you much,

 

[Moloch]

Hello All,

I was thinking about getting a new video card sometime in the next few months. I run across some 'uncommon' boards like the GeForce 6800 GT 128MB and I begin to wonder.

How much on board memory do I need for each resolution, AA, and AF combo? What would a good formula be?

(Height in pixels) x (Width in pixels) x (bit depth) = starting point

Older style super sampling (if I understand correctly) was easier but how much extra memory does the newer types of AA use? Heck does AF use any extra on board memory?

After that is done, what are some basic loads that game textures occupy for say, DirectX 6, 7, 8, 9, and Very High 9?

With all this, I might be able to make a simple baseline chart that has the minimum resolution/AA/AF that a given video card should be able to handle with no texture thrashing out to main memory.

Thank you much,

You don't want an 128MB GF6GT- it not only has 128MB, but its clocked at 700mhz vs 1ghz.
You need 256MB if you want to play at the highest res with AA/AF, there's no cutting corners.

 

[Pete]

I'm honestly leaning toward 256MB on any new, midrange or higher board. I've seen the level of detail in HL2, and I don't want any less in my games. Couple that with the fact that even that crippled GT is capable of smooth gameplay at 12x9 with AA, and 256MB becomes more of a requirement than a nicety.

The math for MSAA is fairly straightforward, IIRC, and has been discussed many times here. I think you just multiply the back and Z-buffers by the number of samples. Assuming I'm not wrong:

1024*768*32bits*(1byte/8bits)*3[front, back, stencil buffer]~=9.44MB

So, 2x MSAA would require basically twice that, and 4x, basically four times that. Things get hairier at higher resolutions:

1600*1200*32/8*3~=23MB

So 2x MSAA brings you up to 40MB, and 4x up to 60MB. At this point, you'd best be bringing 256MB, or nothing at all.

The tricky thing is how much memory the game itself requires, so you can know precisely if your card will have to hit system RAM or--heaven forbid--the HD. Benchmarks show that HL2 will make use of more than 128MB. Obviously, multiplayer games will require even more memory (I'm guessing this is partially why CSS only includes one outfit per side ATM, tho surely insufficient artists is another factor). So, if you like playing with AA and the texture slider all the way to the right, go for 256MB. If you're OK with slightly blurrier textures, you can settle for 128MB (meaning, trade some looks for some speed).

 

[mczak]

The math for MSAA is fairly straightforward, IIRC, and has been discussed many times here. I think you just multiply the back and Z-buffers by the number of samples. Assuming I'm not wrong:

1024*768*32bits*(1byte/8bits)*3[front, back, stencil buffer]~=9.44MB

So, 2x MSAA would require basically twice that, and 4x, basically four times that. Things get hairier at higher resolutions:

1600*1200*32/8*3~=23MB

So 2x MSAA brings you up to 40MB, and 4x up to 60MB. At this point, you'd best be bringing 256MB, or nothing at all.

I think you're slightly wrong, front buffer stays the same size regardless of MSAA setting. GFFX cards could do the "downsampling" of the frontbuffer at scanout (for 2x modes only iirc?), ati cards couldn't to this with the last generation. I'm however not exactly sure if GF6 can still do it, but with 128MB cards it would probably be a bad tradeoff.

I'm honestly leaning toward 256MB on any new, midrange or higher board. I've seen the level of detail in HL2, and I don't want any less in my games. Couple that with the fact that even that crippled GT is capable of smooth gameplay at 12x9 with AA, and 256MB becomes more of a requirement than a nicety.

I'd agree with that though were exactly do you draw the line?
On cards like X800Pro and up, GF6800GT cards and up, I would certainly say don't accept anything less than 256MB (cards with those chips and only 128MB ram sound fishy anyway since they aren't quite official). OTOH on cards up to the 6600 and 9700Pro or so more than 128MB is just a waste of money.
Even with cards like 9800Pro, X700Pro, 6600GT, 6800nu I would still strongly lean towards a 128MB card, as the price difference imho is usually just too big, you'd only be able to increase the quality settings/resolutions in very few apps due to more memory.
For the X800, you could argue it's worth having 256MB of ram, however this also means it is no longer price-competitive with the 6600GT at all, so a 128MB X800 might still be worth a look. It's not like you'd have a choice though, as board vendors seem to have decided they'll only make 256MB cards anyway and price them through the top of the roof...

 

[Ailuros]

On cards like X800Pro and up, GF6800GT cards and up, I would certainly say don't accept anything less than 256MB (cards with those chips and only 128MB ram sound fishy anyway since they aren't quite official). OTOH on cards up to the 6600 and 9700Pro or so more than 128MB is just a waste of money.

I agree. On today's mainstream cards there will most likely kick in other limitations for ultra high resolution gaming with 4xAA before the framebuffer size.

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Benchmarks show that HL2 will make use of more than 128MB.

Apparently it does. There's an application that attempts to read out card and agp memory consumption called Video Memory Tester. Albeit the results aren't at any price reliable, since it fetches the report from the driver, it gives me the following for an unlocked/overclocked 6800nonU/128MB in 1600*1200*32:

4xAA (43.3 fps) card memory 117MB, agp memory 111MB = 228MB
2xAA (59.5 fps) card memory 117MB, agp memory 71MB = 188MB

Ironically even just loading the game and exiting afterwards gives the following values:

card memory 77MB, agp memory 5MB = 82MB

Results don't have to be accurate, yet could serve as an indication.

 

[Pete]

I think you're slightly wrong, front buffer stays the same size regardless of MSAA setting.

You're right. I actually corrected myself in my explanatory text before I posted, but I left the formula incorrect.

As for the memory issue, both HL2 and CSS seem slower and jerkier with high texture quality on my 128MB 9700P--without AA. Dropping to medium adds a few frames and drops the hitches. Though I'm as big a fan of crisp textures as anyone (witness my buying a 9100 over a 4200), extra speed is useless if a 128MB card will pause every so often at my preferred texture settings. Obviously this is a personal preference, and may not hold with all games. I suspect, tho, that newer games will continue to offer max quality texture sets that break the 128MB barrier. As HL2, CSS, and perhaps other games are already there, my recommendation (to a HL2 player) would be to aim for 256MB.

Ailuros, see what I mean? When you say "loading the game," though, I assume you're testing the default 3D menu screen, and not the 2D one accessed via the '- console' switch?