FPS is Still King

by Ray Bryden on April 24th, 2010

Well, Black Friday came and went and left me with an Eyefinity upgrade project which I finally was able to tackle a couple of weeks ago.

Unsurprisingly I found it necessary to upgrade the CPU as well since my frame rates in testing were, shall we say, challenged. Of course, I can only really notice slow frame rates during testing when it dips below 40 or so, but anything slower than 60 is prone to have some stuttering during race conditions which makes control a big problem. Smoothest performance and lowest lag happen with the frames uncapped and running stable above 80 fps. To me, I find the graphics quality always come a distant second to having a high enough frame rate.

As an aside I have to say that iRacing is a completely different sim racing experience when you have three monitors – it is spectacular!

I was using the start of Mosport’s backstretch as the benchmark, since that appears to be where my frames per second (fps) plummets as bad as any other track I have come across. With my old AMD 8450 triple core at 5760×1080 it was struggling to reach 40 fps using minimum graphics settings. So I also just boosted my CPU to a AMD Phenom II 955 3.2 GHz, which is the most my motherboard can handle.

Mosport backstretch, baseline fps.

My first test with the new CPU showed a big jump, to 68 fps in the same spot. But the ugly graphics left a lot to be desired. I know there’s a fine balance between graphics quality and frame rate, but I decided it was time to figure out what each setting cost in terms of frames. Obviously this test cannot take into account the worst case scenario which is a live race with cars pulling off the grid at the start, but it does give some indication as to which are the settings which are the hardest on the system performance.

Mosport backstretch, new fps.

I will spare you the gritty numbers, but suffice it to say that the settings which bring down frame rates more than 4% in the Dallara IndyCar at Mosport are:

Graphics Setting    fps [%]
Shadows + 2 Pass + More Shadows    -27
Shadows + 2 Pass    -21
Higher Detail in Mirrors    -10
Shadows    -9
Cockpit Mirrors    -6
Far Terrain    -6
High Resolution Car Textures    -6
Reduce z-fighting (flickering)    -6
Uncompressed Car Textures    -5
Objects (High Detail)    -5
Steering Wheel    -5

Surprisingly, none of those resulted in a significant change in the CPU load which was averaging about 60% spread over the four cores (usually two cores were working harder than the other two). CPU and video card temperatures were never a problem during the testing.

All other graphics settings seemed to have very little impact on the frame rate. Clearly these numbers are system specific and each computer will yield different results depending on hardware and drivers, not to mention the other processes running in the background, but it does shed a little light on what things tax a system more than others.

Mosport backstretch, baseline triple screen.

My ATI Radeon 5850 1Gb video card appears to be able to handle any amount of Anisotropic Filtering (AF)  with practically no noticeable change in performance. However, Anti-Aliasing (AA) does bring down the frame rate a little, but the change in performance is identical whether it is done as an in-sim setting or if it is handled by the Catalyst Control Center (CCC). Advanced AA settings bring the video card to its knees, dropping the frame rate by 68% with 8X Super Sampling AA, for example.

Mosport backstretch, new triplescreen.

As a result of my testing I found that I was able to enable the following graphics settings and only yield about 5 fps (7%):

Graphic Setting    Value
Cars    Low Detail
Event    Low Detail
Grandstand    Low Detail
Objects    Low Detail
Frame Rate    No Limit (to reduce input lag)
Trilinear Filtering    On
Anisotropic Filtering (AF)    8X
Anti-Aliasing (AA)    2X
Vertex Shaders    On
Pixel Shaders    On
Advanced Shaders    On
Virtual Mirror    On @ 120 degrees
CCC : Mip Map    Highest Quality

I could win back a few lost fps by disabling ‘Objects’, but I like to have more off-track items to use for orientation and to sometimes act as braking points references. Also the AA brings down performance a little but it is worth it to soften the jagged edges. Other tracks I’ve tested with these settings such as Silverstone and Zandvoort have only dropped to about 85 fps at a minimum.

My next step will be to see how the frame rates drop during the start of a race with lots of cars on track, particularly with a Turn 1 pileup. Wish me luck in avoiding it.

My Specs:
AMD Phenom II X4 955 at 3.2 GHz
4 Gb RAM DDR2 PC800
Sapphire ATI Radeon 5850 1 Gb (driver 10.2)
ASUS M3A78-EM Motherboard (BIOS 2003)
Windows 7 64 Bit freshly installed
iRacing running at 5760x1080x32 (triple screen Eyefinity)