RIVA TNT2 and performance
One of the most weak points of TNT was the low fillrate. You
could hit his limitation very easy at high resolutions in 32Bit color depth. Independent
how fast your system CPU is you canīt get higher values than 30fps with a TNT at
1024x768-32 (a bit more by using tripple buffering). The chip was not able to handle that
much data that occurs at that resolution and color depth. And the amount of data is
growing the higher the resolution is. So you could also hit the TNT limit at 16Bit - if
you had a fast system CPU. The limit of the TNT2 is way higher. The TNT2 is double fast in
1024x768-32 than the TNT. A TNT2 ULTRA can achieve about 70fps here. This is made possible
by the much higher fillrate:
Left RIVA TNT, right RIVA TNT2 ULTRA (3DMARK99 MAX)
But those framerates are only a maximum. Youīre
wrong if you think that all games run double fast by only using a TNT2 instead of a TNT. A
big problem here is the CPU-weight of games. For example the game Kingpin: You canīt see
a big difference between TNT2 and TNT here because the card can only display the
information that comes from the CPU:
The image on the left shows the points
(Edges) that are set up by the system CPU. This is called geometry setup (defines where a
point is located in the 3D space - bad to see at this image size). This is the data that
comes from the CPU. These points define triangles so the card draws the triangles and
fills them with colors, textures and effects.....this is only a simple model of how it
works today.
Games like Kingpin use a lot CPU power for internal game
calculations (opponent intelligence, effects...). So the CPU does not have enough power
left to feed the graphic card. You can notice that when you change the resolution in the
game (800x600 -> 1024x768). The results are nearly the same because the CPU power left
for the graphic card is the same. You can only take advantage of the new power of the TNT2
if the amount of data that comes from the CPU is large enough.
This means that you should have at least a 400MHz intel CPU
(Pentium II/Celeron) if you want to buy a TNT2. The performance on an AMD K6-2 350MHz
system is really bad (see benchmarks). There is nearly no difference between TNT and TNT2
ULTRA results. No offical release of a 3DNow! capable driver by NVIDIA (announced) is
available yet. So the low FPU power (Floating Point Unit: influences massively the
performance of the geometry setup) of the AMD CPU is a real problem here. The graphic card
does not get enough data because of the CPU bottleneck.
Iīm sorry that I canīt tell you how the situation is on a K6-III CPU with 400 or
450MHz because I donīt have such a CPU. I think itīll perform better because the CPU has
a fast second level cache on die that runs at full clockspeed and there is also the
mainboard cache working as a third level cache. Future games need a lot CPU power
(Unreal2, Quake3) so you need a fast CPU if you want to have fun with a TNT2. The
performance should be accurate on both sides. If youīre going crazy hearing this you
should remember that a 300MHz Pentium II was state of the art when the TNT was released.
At the end you can get a Pentium II/III running at 450MHz or more! The TNT is the
bottleneck using such a CPU. The TNT2 is made to show its performance even on a 600MHz
system with 3D extension (Streaming SIMD or 3DNow!).
This CPU-situation will change when the geometry setup is
transfered to the graphics card. There are announcements that weīll see this technology
at the end of this year.
But enough words now, letīs watch numbers....
RIVA Station 1999 - Lars Weinand |
