Classic A64 3200+ Venice overclocking choices question

[yacoub]

I can run my rig at 240MHz "CPU Frequency" 2.4GHz) (aka bus) with 1:1 memory divider (240MHz x2 for DDR)

or

I can run 250MHz "CPU Frequency" (2.5GHz) with a .83 RAM divider, which drops the RAM to ~208MHz.

Both of these options use 4x HTT Multiplier since 240x5 would be way over 1000MHz but x4 is 960MHz and 250x4 is perfect 1000MHz.

I can probably push the CPU Frequency a bit more since the chip is running cool (~40C idle) and it's at stock voltage (1.4v), but that would require dropping HTT to x3 which would mean unless I can reach over 300 CPU Frequency, it wouldn't be very worthwhile since I'd lose the HTT speed. I could drop the CPU Multiplier though to counteract that.

So many choices! What's the best goal? ie, which of these parts is the bottleneck that shows the most benefit from being raised (or simply not lowered) - CPU Frequency, RAM ratio, or HTT speed being at or near 1GHz?

When I use the program here: http://math.gogar.com/athlon64.cgi
(with values 2500, 240, 1000, 250, 10x (3200+))
I get these results at the top:

HTT ----- CPU ------------------- Memory ------------------------------- Hypertransport = RESULT (lower is better result)
250 -----10 x 250 = 2500 -----11:12,183,DDR366 = 227.27 (DDR455) -----4 x 250 = 1000 = 0.2812 [NOT AN OPTION FOR ME, no .83 DIVIDER]
250 -----10 x 250 = 2500 -----5:6, 166, DDR333 = 208.33 (DDR417) -----4 x 250 = 1000 = 1.7409
240 -----10 x 240 = 2400 -----1:1, 200, DDR400 = 240 (DDR480) -----4 x 240 = 960 = 16
240 -----10 x 240 = 2400 -----13:12,216,DDR433 = 240 (DDR480) -----4 x 240 = 960 = 16


Note that Asus A8N-SLI Premium does not offer a .83 divider so I cannot get the best of both worlds of a 2.5GHz overclock AND DDR455 RAM speed. I have to choose either 2.5GHz and DDR417 or 2.4GHz and DDR480. I am being told the RAM speed is more important, even with the slightly slower HTT of 960MHz.

 

[Gautama2]

Does lowering the HTT multiplier have noticeable perforamance change? I was under the impression it didnt.

 

[yacoub]

Well HTT is currently running at 782MHz at 3x multiplier. I'm not sure how much performance impact that has compared to it running at 1000MHz. What uses the Hypertransport bus most? Is it ever saturated?

I'm at 2.6GHz (10x260) at 1.45v, which with the 333 ram divider makes the ram at DDR434.
I could do 2.5GHz (10x250) at 1.40v, which with the 333 ram divider makes the ram only DDR417, but HTT is 1000Mhz then instead of 782MHz.
I can also do 2.4GHz (10x240) at 1.40v, which with the 1:1 400 no ram divider, makes the ram DDR480 and HTT at 960MHz.

I could also start experimenting with a lower cpu multiplier.

update: well, 2.6GHz wasn't stable in game testing. Locked up pretty quick in CS:Source.

Went back to 2.4GHz (10x240), which gives the best memory clock anyway and still HTT pretty close (960MHz). I think it's happiest there.

 

[n7]

Okay.

First off, HTT (Hyper Transport Tunnel) is as FSB is to Intel.

You are calling the HT/LDT (Hyper Transport)/(Lightning Data Transport) the HTT, which is incorrect, AFAIK.

HT (Hyper Transport) speeds on AMD do absolutely nothing for performance.
Nothing at all.
So just lower it to 4x or even 3x (listed as 600 /800 on some mobos), & forget about it.

RAM frequencies also mean quite little for A64 systems, mainly due to the CPU's integrated memory controller.
IOW, in order of importance when OCing:
1. CPU frequency (CPU multi x HTT)
2. RAM timings
3. RAM frequency
4. HT speed (this seriously doesn't matter though)