CAS 1.5 vs CAS 2.0 vs CAS 2.5

[GreenBeret]

I have always been wondering about the real effect of CAS setting on performance, especially since I got my Pentium 4 rig. The following is my little review on that

Configuration:

CPU: Intel Pentium 4 1.6A @ 2.75GHz (172.5x16)

Motherboard: Abit BD7-II RAID (AJ BIOS)
Settings: PCI bus = 33 MHz
System BIOS cacheable = Disabled
Video BIOS cacheable = Disabled
Video RAM cacheable = Disabled
AGP speed = 4X
AGP Aperture Size = 64 MB

RAM: Samsung "CTL" PC2700
Settings:
RAS to CAS Delay = 2
RAS Precharge = 2
Cycle TIme (Tras) = 5
Enhance DRAM Performance = Enabled (DRAM Idle Timer = 0)
FSB:RAM = 1:1

Graphic card: ATI Radeon 8500
Settings:
Clock speed: 301.5 Mhz core / 301.5 MHz memory
BIOS: 1009
Driver: Catalyst 2.3 ver 6166

HDD: Seagate Barracuda IV on HPT 372 RAID controller

OS: Windows XP Professional

3D settings:
Resolution: 1024x768 x 32 bit, 120 HZ
FSAA & AF = OFF
Texture and Mipmap quality = Highest
VSYNC = OFF
TruForm = OFF

If the difference is under 2 fps, it is insignificant and within the error margin.
I don't run the game tests at 640x480x16 bit (so that the video card is no longer the bottleneck), as nobody plays games at that resolution, and I want to see the performance benefit that the CAS setting brings at the most frequently use resolution: 1024x768x32bit.

OK let's benchmark !

Sandra 2002 Pro mem:

cas 1.5: buffered: 2654/2653 unbuffered: 1376/1379
cas 2.0: buffered: 2654/2654 unbuffered: 1403/1399
cas 2.5: buffered: 2653/2655 unbuffered: 1407/1398

Comment: I'm very surprised with the cas 1.5 unbuffered result. I have reran the test many times to confirm it. Strangely, the result is always worse than cas 2.0 and cas 2.5

Science Mark 2.0 beta:

cas 1.5: 2444.72 MB/s
cas 2.0: 2474.04 MB/s
cas 2.5: 2458.65 MB/s

PCMark 2002:

cas 1.5: CPU = 6779 / Memory = 6471
cas 2.0: CPU = 6776 / Memory = 6484
cas 2.5: CPU = 6795 / Memory = 6508

Comment: Again, I'm very surprised that cas 2.5 gives the highest score !

3DMark 2001 SE:

cas 1.5: 10600 Car Chase: 166.8/68.0 Lobby: 166.8/79.8
cas 2.0: 10572 Car Chase: 167.3/66.5 Lobby: 165.9/79.5
cas 2.5: 10621 Car Chase: 169.5/68.4 Lobby: 166.3/79.4

Comment: Car Chase and Lobby are the two most CPU and memory intensive tests in 3DMark. The highest score again is at cas 2.5 !

UT2003:

cas 1.5: Flyby = 131.0 / Botmatch = 65.0
cas 2.0: Flyby = 131.6 / Botmatch = 65.0
cas 2.5: Flyby = 131.6 / Botmatch = 65.0

Comment: The scores are identical, even in the Botmatch test, which is very CPU and memory intensive

AquaMark v 2.1: Texture = 24MB, Pixel Shader = ON.

cas 1.5: min 36.8 max 79.4 avg 56.2
cas 2.0: min 33.7 max 81.2 avg 55.8
cas 2.5: min 31.9 max 80.2 avg 55.5

Comment: It seems that CAS does affect the minimum fps, CAS 1.5 is the fastest, and CAS 2.5 is the slowest in this case.


Commanche 4: DXTC = On, AUDIO = OFF, SHADERS = ON

cas 1.5: 42.8
cas 2.0: 42.3
cas 2.5: 42.1

Comment: Commance 4 is known as a very CPU intensive benchmark. It seems that changing the CAS setting doesn't help much in performance, although CAS 1.5 is the fastest and CAS 2.5 is the slowest in this test.


Note: I will test the RAM at 3:4 soon.