FSB vs. Multiplier - This makes no sense!

[NeoMoses]

Ok, I'm a little confused now. I've been overclocking for about a year now, and thought I was past the newbie stage, but obviously not.

Here's my problem. I just got an unlocked 1.2 AXIA and was playing with it. it hits 1400 pretty well. I'm just wondering which 1400 is the fastest. I first tried 10.5X133. It Worked. So next I tried 10X140. worked. then 12.5X110. worked.

All of what I have read and heard would say that the 10X140 would be the fastest. According to Sandra, just the opposite is true. Here's the CPU Benchmarks from Sandra. (Dhrystone/Whetstone)

10X140: 3926/1902
10.5X133: 3942/1913
12.5X110: 3967/1943

The Cpu Multimedia benchmarks follow the same pattern with 10X140 being the slowest, 12.5X110 being the fastest. In actual use, I could tell no noticeable difference between any of these 3. What I'm wondering, which would be the fastest setting for encoding DIVX, for encoding MP3, and for normal everyday use. (MSOffice, Adobe Photoshop, Macromedia suite....)

I guess my real question is why does Sandra show higher FSB=slower for a given speed? And why would thousands of overclockers strive for high FSB if it truly is slower (Unless it's the AOL Effect - Everyone thinking, "surely millions of people aren't that dumb!" :D )

Here's my system specs FYI:

Asus A7V133-RAID
1.2 Tbird (unlocked) at 1400 (10.5X133)
512 MB Crucial PC133
80 GB 7200 RPM WD HD
Hercules 3DProphet 4500 (Kyro II, w/ TVOut)
Sony CDRW, Creative DVD-ROM
Realtek ethernet card.
300W PowerSupply

[NeoMoses]

just an update. I'm gonna go through many combinations around 1375-1450 MHz, see how the Sandra Benchmarks turn out, and post them later. hopefully this'll clear up any confusions.

[jbell]

what about 10.5x140? :)

I agree though the higher FSB with lower multiplier *should* be the fastest setting....

[_Will_]

But what about your memory benchmarks/multimedia? My guess is that the better performance you'd get from those would make the Dhrystone/Whetstone differences pretty negligable.

[UnseenMenace]

The benchmark tests you are doing are CPU intensive and not respective towards the complete system performance. If you try a system intensive benchmark the results should swing the other way as data is transfered across the motherboard faster as the FSB speed increases

[oc jason]

yes the higher the multiplier the better CPU benches will be, the higher the FSb the higher teh MEM benches will be, you WILL feel the higher FSB , more than teh higher mulitplier

[dugans]

Makes sense to me: high multiplier means the cpu works harder, high fsb means that the rest of the system works harder.

The rigs I've messed with the most show better oc's with a higher multiplier, but the overall system performance is slower:
When setting up my rigs now I go for multiplier first, then after finding the highest stable speed I go back and try to achieve the same oc with as much fsb as possible.

[Alex99]

Higher FSB makes your memory runs at a faster speed, thus your memory throughput increases. Today's higher power CPUs like the Athlon are starving for data from memory. Most of the time the CPU sits on idle cycles while it waits for data from the memory. So you want to run as high an FSB as possible. Just run the Sandra memory test and you'll see. Those small differences in your CPU scores are way smaller then even margin of errors, I'd run the CPU benchmark several times and take the average. You said your main concern is improving DivX and MP3 encoding, and Photoshop. Well, those are the most memory bandwidth hungry apps out there, they will definitely benefit from faster memory resulting from higher FSB.

[NeoMoses]

Ok, here's an update:

I'm currently running stable at 10.5X138. I can also run stable at 10X144. I've tried 9X150, but that's a no go.

So I'm posing the question: for the given apps (adobe photoshop, all macromedia stuff, DivX, mp3) which combination of multiplier/FSB would be fastest? Please rank in order from fastest to slowest. Here's my best guess.

10X144
10.5X138
10X140
10.5X133

thanks for all the help! (also, I guess i need to update my sig!)

[Silver]

ocjason makes sense to me and is what I have experienced. Higher fsb you feel, higher multiplier you feel as well but not as much. Cpu intensive go with multiplier, otherwise I would go with the fsb as real world usage for me is a faster "feel".