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AGP4X vs. AGP8X
An anonymous reader writes "With upcoming chipsets such as the SiS648 claiming support for the latest AGP8X standard, we asked ourselves if there were any performance benefits. We took the SiS648 and Xabre 400 reference boards, modified them and compared the results." I can't even get 4x stable under XP, so I figure 8x is
half as likely to let me play NWN :)
Basically, SiS has come out of nowhere with motherboards that absolutely trash the competition in regards to performance and features. It started last year with the SiS 735, the best performing Athlon mobo of the year. Sadly, it was a poor overclocker, so it was shunned by AMD fans. But this year SiS has had a string of hits. It's the only 3rd party with a P4 license, which makes it the only choice for mobo manufactures in terms of 3rd party P4 mobos (obviosuly they're ansty about Intel frowning upon their Via-based P4 boards, seeing as Via doesn't have a valid P4 license). The SiS 645, 645DX, and now the 648 have consistently been of high quality with features no one else has. The 645 introduced MuTIOL which doubled the bandwidth between north and south bridges, to 533MB/s. The 645DX introduced unnofficial, rock solid DDR400 support. Now the 648 again doubles bandwidth between north and south bridges to 1 GB/s, it introduces AGP 8x, and it probably will officially support DDR400. SiS 648 boards also have Serial ATA support. This is a far cry from a decade ago, when everyone knew SiS=shit.
I hate it when I forget passwords.
I doubt 8X AGP is going to make a really big difference, at least not for a while to come. This comparison is using mostly synthetic benchmarks, not actual games. These sorts of benchmarks usually tend to show a more pronounced gap in performance than do real games. Actually if you look at a few of the benchmarks for Serious Sam and Quake3, 4X AGP is actually benchmarking nominally faster than 8X.
They should've tested with some more modern, more demanding games to give a clearer picture on whether or not 8X is actually much of a help or not. They're right though, we're going to have to wait until the RADEON 9700 and NVIDIA's NV30 before we can tell whether or not it really is going to make a difference. I'm putting my money on "no."
I have a ATI AIW 32MB DDR, and my tribes2 can get a lil laggy esp when their are some vehicles on my screen.
reading my X log I notices that DRI was using 1X mode for AGP. after some RTFM, I found the option to kick it into 4x.
Anyway the point being it didn't help speed up the game gfx (well i didn't notice much difference)
In case ur wondering for ATI cards the XF86Config option is:
Option "AGPMode" "4"
Also i noticed:
Option "AGPSize" "32"
But i cant tell if setting this bigger then the ram on the card helps or not (maybe that the buffer size opt?), was hoping to let the card borrow more of my sys ram (which is pc100, slow compared to gfx cards DDR, but better then hdd =)
anyone know any other good opts to help eek more speed?
With 3D Games, screen resolution isn't really an issue. The screen resolution and how much you need to saturate the AGP bus are completely independant. The only thing that determines the AGP bus saturation is how much geometry you need to send and how efficiently you can send it. How many textures you need to send and how efficiently you can send them.
With texture memory creeping upwards in 3D cards we should eventually see a point where all textures can be stored on the card and sending textures over AGP should be rare.
However, sending geometry is usually done per-frame in most 3D games, and you'd be surprised how much all of those triangles can add up.
1M triangles, with 3 vertecies, 3 texture coordinates, 3 normal vectors and sometimes more per vertex with each vector being comprised of 4 floats and each float of 4 bytes.
1,000,000 * (3 + 3 + 3) * 4 * 4 = 144,000,000
That's 144MB per frame. At 60 frames per second that's 4.22GB per second.
Now, granted, 1M tris per frame is way high for today's games. Most current games push around 30k per frame, never more than 60k. My friend and I are doing closer to 300k and are already starting to become AGP-bandwidth-limited.
Anyway, you are right. You can't have too much bandwidth to your video card. I'd love to be able to push a full 1M tris/frame, and I'm sure I will be able to soon. Just not yet. And not even with AGP 8x in all likelyhood.
Justin Dubs
SiS has been doing motherboard chipsets since at least the 486 era, and I/O cards before that. I've also had SiS-based motherboards, and they had bugs and instabilities I'd never even heard of before. I've long since come to associate SiS chipsets with the mobo mfgr cutting corners, and haven't seen anything yet to make me change my mind. (Tho the SiS-based I/O cards for 386/486 machines seemed to be pretty good in their day.)
... gee, I wonder if that's why SiS chipsets need heatsinks, even when no other chipset in the same class needs 'em.
As to another poster who says he likes SiS because of the "low heat/low power"
~REZ~ #43301. Who'd fake being me anyway?
--
Power to the Peaceful
Where have you been? I have a ECS K7S5A with an SiS 735. The northbridge runs cool to the touch. Other chipsets require a heatsink fan. Shouldn't bother responding to trolls.
Just a Tuna in the Sea of Life
right... so they DON'T DO THAT. Even 8X AGP is going to be very, very slow compared to the incredible speed of the RAM in most of the high-end video cards. There have been a few demos using AGP texturing, but all the real-life apps I'm aware of are carefully constructed to stay within that cache.
It may help doing background loads of 'seamless transition' games, but even so.... unless you're trying to stream all these textures out every frame, it's not likely to help much. AGP 4x can fill a 128MB card in 1/10th second; 8X can do it in 1/20th. Unless you get to the point of multiple updates per second, it's just not going to matter very much. Developers will use good caching algorithms and reasonably careful level design to work around AGP speed issues.
Streaming textures IS a pretty cool idea, and I would like to see games that use them. Maybe Doom 3 will, but it hasn't sounded like Carmack is trying to do anything like this yet.
The reason I was so acerbic in my original comment was that the website was talking like it mattered NOW, for the apps we have TODAY. (a whole 4.7% increase! in one benchmark! wow!).
In a nutshell: for everything out now and probably for another 18 months, AGP8X isn't going to matter a whit. Don't worry about it until 2004 sometime.