Ocing Quandry

[royalk4]

Thought the title might provoke a few more viewers

I have a couple of quick questions on OCing my system, as listed below.


I am currently running my HTT at 250MHz and my HT multiplier at 3x( front side bus for my mobo is 800) and my memory I have set to 200MHz but for some reason if I leave the HTT at 200MHz the RAM runs at DDR333 instead of 400. I know this has something to do with the fact that its a s754 system.

I've also read a few OCing Guides and one for s754 and noticed that in his,s754 guide, the max he could get was 250HTT before his memory would become the limiting factor. I apparently don't seem to have this problem??? but I am confused as to why it was so easy to run the HTT at 250? Did I do something wrong that could damage my system?? If it's possible to raise my Memory I would love to, maybe I could hit 3GHz??

Let me know if I'm doing something wrong please

 

[5t3v0]

What GeIL memory do you have? My last memory was GeIL value GE1GB3200BHDC with the 2.5-3-3-6 timings. The maximum speed I clocked this to was 237MHz which was with cpu on 9x290HTT and memory on a 166 (5:6) divider. My cpu needed a lot of volts (1.65v) to run at this HTT so I lowered to 280 which on the same divider gave 229MHz on the ram. At this speed I could run on tighter timings of 2-3-3-6. To get these speeds I had to raise the vdimm to 3v (showed as 3.05v on my board) which sounds like a lot but those GeILs just loved high volts - you'll note that they're rated to 2.95v!

I'm not sure how high the 3700+ can go but you could try raising the HTT to 280, lowering the multiplier to 10 to give 2.8GHz, and use a 166 divider to give 233MHz on the memory which it should be able to handle. Is the HT limited to 1600 on 754? You might need to lower the HT multi to x2.

 

[royalk4]

I believe it is limited to 1600mhz. I'm not sure the box and manual say 800 but I don't know if that is base speeds or double speeds or what??

 

[5t3v0]

LDT (aka HT) = HTT x LDT (HT) multi X 2. In your case 250 x 3 x 2 = 1500. The x2 is because its bi-directional like DDR RAM. The 800 quoted in your manual will be the single speed, so it will be limited to 1600. Maybe later BIOS revisions increase this to 2000.

 

[royalk4]

that was going to be my next question thanks. so 800MHz FSB=160MT/s FSB?

 

[5t3v0]

The terminology is a bit confusing. Here's a bit I pinched from i4memory that shows it a bit better than me:

AMD64 3700+ s754 cpu default is:
HTT = 200mhz
Multiplier = 12x
Raw cpu speed = 12x 200mhz = 2400mhz
LDT = 4x
HTT Bus speed = 200mhz x 4 x2 = 1600mhz

The rules you need to observe are not to exceed the 1600MHz HTT Bus speed, and to use a divider to keep your memory frequency within it's limits. There's a tool called A64MemFreq which will help calculate what the memory frequency will be based on HTT, cpu multi & mem divider.

EDIT: Have you considered that you may have reached the limit of the cpu at 250HTT?

 

[royalk4]

I just set the HTT there so that my memory would go back up to 200mhz. It was an arbitrary value... I've yet to really get into OCing. I know that whenyou have 2 sticks of RAM in a 754 board they ram is automatically downclocked to be read and 333mhz instead of 400mhz. So I lowered the Multi and raise the FSB to 250 so that the RAM would be back at 200mhz. IN the next couple of hours I'm going to downclock the ram all the way and see what my cpu can get for HTT on it's own.

WHen I raise the HTT I need to make sure and lower the LDT right? so the max I could HTT I could get at 3x would be 266. Also is it safe to go down to LDT of 2x? I doubt I would need to.. but if for some freakish reason would that be unsafe?

 

[5t3v0]

I would recommend dropping the LDT to x2 so that you can at least rule that out as a limiting factor. There's a lot of threads in the forums that say the HT bus is not that influential on performance since it is rarely ever maxed out. If you can raise the HT voltage on your board, that might also be worth a try. I cant on my board which is frustrating. When I am testing new overclocks, I tend to boot into memtest rather than windows & run a pass of that before loading windows & testing on Prime95.