Overclocking for AE

[Akashio]

Does anyone know how the Ram Mhz speed interacts with the HTT bus on an Athlon 64?

Like if my HTT bus was 285 why do I need to lower my Ram speed to stablize the system? And if I do lower the speed from 400 to 333, what is the real Mhz value?

In short, how do the HTT bus and Ram clock speed interact with one another?

[[Mike of the Desert]]

I have a friend that would answer this question like "what time is it?", now is in vacation, when he'll return, be sure I'll contact you.

[dwchang]

Does anyone know how the Ram Mhz speed interacts with the HTT bus on an Athlon 64?

Like if my HTT bus was 285 why do I need to lower my Ram speed to stablize the system? And if I do lower the speed from 400 to 333, what is the real Mhz value?

In short, how do the HTT bus and Ram clock speed interact with one another?

Simple summary, your Front-side bus and HTT should be running at a similar frequency. This is to make RAM transaction not get stalled. Effectively if one thing is running at say X and another at X + Y (i.e. faster) that means the 2nd component would have to wait for the first. Basically it leads to the 2nd component not being fully utilized.

Basically you want your frontside bus and RAM speeds to be the same (i.e. 200/200 or 400/400, etc. etc.)

I hope I'm understanding the question correctly.

[Zero1]

If your ram is rated as pc3200, or DDR400, it's actually running at 200MHz.

If you want to run your FSB at 285, you'll need set a divider, or a limiter in the BIOS.

[Akashio]

If your ram is rated as pc3200, or DDR400, it's actually running at 200MHz.

If you want to run your FSB at 285, you'll need set a divider, or a limiter in the BIOS.

I guess what I don't understand is what this divider is or how to locate it in my bios.

I guess what confuses me is this:
If my HTT bus (similar to FSB) is 245, with my DDR400 set at 400Mhz, I know my RAM is running at 490Mhz effective. However, if I go over 250, my ram fails until set to "333Mhz." Now I know because of the HTT bus speed my ram is running higher than 333Mhz, but I don't know how to figure out by how much. How do I know?

I need to know so that I can smartly balance the overclock of the CPU and RAM to get the best system overclock possible.

Thank you guys for continuing to help me!

[Zero1]

If your ram is rated as pc3200, or DDR400, it's actually running at 200MHz.

If you want to run your FSB at 285, you'll need set a divider, or a limiter in the BIOS.

I guess what I don't understand is what this divider is or how to locate it in my bios.

I guess what confuses me is this:
If my HTT bus (similar to FSB) is 245, with my DDR400 set at 400Mhz, I know my RAM is running at 490Mhz effective. However, if I go over 250, my ram fails until set to "333Mhz." Now I know because of the HTT bus speed my ram is running higher than 333Mhz, but I don't know how to figure out by how much. How do I know?

I need to know so that I can smartly balance the overclock of the CPU and RAM to get the best system overclock possible.

Thank you guys for continuing to help me!

First off, it's probably easier to refer to RAM as it's true speed (ie 200MHz not 400), just makes calculation easier.

When you are setting a RAM speed in the BIOS, you are setting the divider. Say for instance you set the RAM to 100MHz in the BIOS, well the BIOS calculates the ratio assuming the FSB is 200MHz, so setting the RAM at 100 MHz will cause it to run at half the speed of the FSB. Then if you upped the FSB to 250 the RAM would then be running at 125 MHz.

Same with setting the RAM at 166MHz, since the FSB should officially be 200 MHz, the ratio between the two speeds is 1.20. In this case it's FSB/1.20 = MEM. Another way if you know the fraction is FSB/6*5 = MEM. If you wanted to find the fastest FSB speed you could run at with that divider without running the RAM over spec, just do MEM*1.20 = FSB or MEM/5*6 = FSB.

Recently I was running my FSB at 306*8 (Prime95 stable too, not bad for an Athlon64 3400 ) with the memory set at 133MHz in the BIOS. Since the divider is calculated based on 200MHz, it gives me a 1.50 or 3/2 ratio. So to sum it up, 306 FSB/1.5 = 204 MEM or 306 FSB/3*2 = 204 MEM.


Now at the sort of speeds you are wanting to achieve, your HT link will be nearing 2000, and the official speed is 1600. It may be your board just can't cope, my old Epox couldn't, it would die around 1800. You will need to alter the HT multiplier in the BIOS too, put it to something like x3. Note the speeds I talk of are a sort of full duplex mode or something, the default is 200FSB*4=800HT(*2=1600HT) and so if you are using 245 you will have something like 245FSB*4=980(*2=1960HT). By dropping the multiplier to x3 you will actually be undershooting the default HT speed so you now have room for experimenting.

I was lucky with my board, my absolute max was 282FSB*4=2256HT).

Many things are dependant on the FSB speed for the computation of it's speed. In quite a few BIOSes things like the PCI bus and AGP bus are clock locked, so they don't exceed that speed even if the FSB is altered.

200 FSB * 1:1 = 200MHz Memory (DDR400)
200 FSB * 4 = 800 HT (1600 Full duplex)
200 FSB * 11 = 2200 MHz CPU (Athlon 64 3400+)

If I were to alter it to use the fastest FSB speed available to me, I'd use:

306 FSB * 2:3 (133MHz) = 204MHz Memory (DDR408)
306 FSB * 3 = 918 HT (1836 Full duplex)
306 FSB * 8 = 2448 MHz CPU (Athlon 64 3400+)

272 FSB * 7:10 (140MHz) = 190MHz Memory (DDR380)
272 FSB * 4 = 1088 HT (2176 Full duplex)
272 FSB * 9 = 2448 MHz CPU (Athlon 64 3400+)

245 FSB * 5:6 (166MHz) = 204MHz Memory (DDR408)
245 FSB * 4 = 980 HT (1960 Full duplex)
245 FSB * 10 = 2450 MHz CPU (Athlon 64 3400+)

This might be of help, can't remember where I got it, I've got a feeling it was someone on hard forum. I got to say though, it went fine for me but be warned, you could damage your system doing this, think twice if you are unsure (that message to anyone reading)

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There are a couple of things to do to maximize your overclock:

1. find the maximum cpu clock speed
· set the memory to 133mhz in the bios
· set the vcore to 1.70v
· set the memory to 2.80v
· set the HT to 2x or 3x
· in windows us clockgen to increase the HTT with the default multiplier
The idea of this step is to determine the maximum o/c of the CPU by ruling out memory or chipset limits.

2. find the maximum HTT speed
· set the memory to 133mhz in the bios
· set the vcore to 1.70v
· set the memory to 2.80v
· set the chipset voltage to 1.70v
· set the HT to 2x or 3x
· in windows us clockgen to increase the HTT with the lowest multiplier that will work on your CPU

The idea of this step is to determine the maximum HTT of the motherboard by ruling out memory or cpu limits. I've found the maximum HTT is usually about 1000mhz give or take... my system is at 4x245=980, others have hit 3x300=900

3. find the maximum memory speed.
· set the memory to auto in the bios and default memory timings
· set the vcore to 1.70v
· set the memory to 2.80v
· set the chipset voltage to 1.70v
· set the HT to 2x or 3x
· in windows us clockgen to increase the HTT with the lowest multiplier that will work on your CPU

The idea of this step is to determine the maximum memory speed using the SPD programmed into your memory ruling out chipset or cpu limits.

Now you have to mix and match the different HTT, memory speeds/timings, HT multipliers to get as close to the maximum cpu o/c as possible. Do some benchmarks to determine which combination gives the best performance.

Some sound advice IMO, but I did warn you people

Of course don't be too ambitious until you figure out something that's stable, trust me, I've fried nice CPUs back in the day; not expensive but CPUs all the same. Run Prime95 torture tests too, it's very thorough if your OC can stand Prime95, it's pretty damn safe IMO.