Confused by FSB/HTT

Hey guys and gals,

I am new to overclocking, and new to AMD as well, so please bear with me if this sounds stupid, but...

I just recently purchased:
eVGA nForce4 NF41 mobo
Athlon 3800+ X2 (Manchester) - stock HSF
2X512MB OCZ PC3200 Platinum Rev 2 (TCCD)
Geforce 7800GT (stock)

After playing around for 2 days with HTT and voltages all over the place, it seems that my rig was mostly stable at 240HTT. Running CPU multiplier at 10, running at 2.4GHz. Running memory at 2-3-3-6 1T at 1:1. Running at 250 required me to loosen timings or run a divider on memory and actually benched lower.

What's interesting is that when I ran the HTT multi at x3 (720FSB), my Sandra CPU and memory were at 20263/6304 for Drystone CPU/Memory Bench. When I upped the multi to x4 (960FSB) all other elements the same, the scores were 20255/6272!

What does the increased FSB do for the system? Even in gaming, Half Life 2 and Far Cry played smoother on the 720FSB. Far Cry BSOD-ed at one point at the 960FSB point after about 45 mins.

Did I misconfigure something?

(By the way, anyone thinking of the eVGA NF41 board that comes bundled with the eVGA 7800GT card, it looks like mine tops out at 265FSB (x8 CPU) before losing stability and needing the CMOS cleared).

Thanks in advance as always!

It's commonly explained this way, so this is the way I will attempt to explain it. Lets say you have a 5 lane highway with 4 cars traveling it. Increase that highway to 8 lanes. Have you increased the flow of traffic ? No, because the highway was far from filled up to begin with. The hypertransport bus is like that. You could have it as low as 600mhz without any negative effects on bandwidth. The only problem, is if you go too low, or too high, the system might not boot. anywhere from 600 - 1000 should be fine. Try not to go above 1000 with it anyway

Hope this helps!

Jason.

Wow, i'm a little suprised that 17 people viewed this thread before me, and no1 answered.

J.

That was a good answer though.

Yuriman said:

That was a good answer though.

Click to expand...

Yes it is, thank you!

As far as my overclock, is it possible my mobo is the limiting factor? From what I've read 2.4GHz on the 3800 X2 is on the lighter side, but the mobo needs the CMOS cleared (has a meter on the mobo telling u the problem) if I go above 265FSB, regardless of the volts or how loose the timings are (with or without divider). Isn't that a little light for the motherboard?

Try setting the CPU multiplier down, and see if the board is limiting you.

Yuriman said:

Try setting the CPU multiplier down, and see if the board is limiting you.

Click to expand...

I tried clocking the multi to x7 at 265GSB (under 2GHz) and it still froze up emough that I had to clear the CMOS. Runs stable at 240 (and 250 with divider) but as soon as I touch 265, POOF!

is it just me or is that a big red light for lower multiplier opterons? (e.g. 144, 165, etc.)

Most boards do not have a problem with high HTT, my DFI is capable of well over 320. Never bothered to test higher.

Yuriman said:

Most boards do not have a problem with high HTT, my DFI is capable of well over 320. Never bothered to test higher.

Click to expand...

Maybe this is why they were giving these boards away 'free' with the 7800GT cards from eVGA...

Nonetheless my 3800X2 at 2.4GHz i enough for me. Afraid to go higher with stock HSF. The CPU hit 56C at 2.6GHz, which is too hot for my blood. At 2.4 it hovers in the high 40s at load.

Also another reason why the ASUS and DFI boards cost more too, they can hit the high HTT. Or mebbe my mobo is just a piece. Or it could be my overclocking skills...

Wait a second. Gautam said, in the A64 101 stickied thread, that HTT isn't a bus where data travels.

Gautam said:

The HTT is, in fact, not a data path or bus, simply an internal time off of which the HyperTransport and CPU speeds are derived.

Click to expand...

In which case, the multi-lane highway analogy makes no sense, as data (the cars) aren't even there, given that HTT is just a number. Another issue is 'too high' and 'too low' HTT. If HTT is "simply an internal time off of which the HyperTransport and CPU speeds are derived", then how can setting it high or low directly cause system malfunction? I understand that it could indirectly if you set it high along with a high CPU multiplier, but I don't see the system crashing because the HTT itself is too high.

Can someone please clarify?