The Newbie's Guide to Overclocking.

[hitechjb1]

Some memory bandwidth estimation

For DDR,
DDR_speed = 2 * memory_speed
max_bandwidth = memory_speed * 2 * 8 = 16 * memory_speed
E.g.
For DDR, FSB = 233 MHz,
DDR_speed = 466 Mb/s
max_bandwidth = 16 * 233 = 3728 MB/s

For QDR (quad pump data as in P4)
QDR_speed = 4 * memory_speed
max_bandwidth = memory_speed * 4 * 8 = 32 * memory_speed
E.g.
For DDR, FSB = 233 MHz,
QDR_speed = 932 Mb/s
max_bandwidth = 32 * 233 = 7456 MB/s


memory_bandwidth_efficiency = measured_bandwidth / max_bandwidth
(For DDR, use Max_bandwidth for DDR.
For QDR, use Max_bandwidth for QDR).


nforce2_effective_bandwidth ~ 0.95 * 16 * memory_speed ~ 15.2 * memory_speed
E.g. FSB = memory = 200, effective_bandwidth ~ 3040 MB/s

QDR_1:1_effective_bandwidth ~ 0.75 * 32 * memoory_speed ~ 24 * memory_speed
E.g. FSB = memory = 200, effective_bandwidth ~ 4800 MB/s

QDR_5:4_effective_bandwidth ~ 24 * 1.125 * memory_speed ~ 27 * memory_speed
E.g. FSB = 250, memory = 200, effective_bandwidth ~ 5400 MB/s

 

[hitechjb1]

OK. Thank you. I do not see ASYNC option anywhere on nforce2 Epox 8RDA+, all I see is BIOS > Advanced Chipset Features > Memory Frequency:
This is where you can adjust percentages but it makes no mention of SYNC.

Please help me out in this current thread:
http://forum.oc-forums.com/vb/showthread.php?s=&threadid=215500

I haven't used a 8RDA+. If it does not have ASYNC and SYNC explicitly, then 1:1 or 100% would mean SYNC. Other ratio would be ASYNC.

From your post in the memory section, I think FSB 204 at 75% would be better than FSB 191 at 80%. Try to up the Vdimm to find the highest speed that memory can go.

You can always try out idea and fine tune system and use benchmark programs such as Sandra to find out which is better.

 

[c627627]

Yes, I understood that. Thank you very much for this very helpful information.

From what I gathered Vcore @ 1.8 V is OK; 1.85 V if you must but higher than that like 1.9xV is really not recommended and will reduce the life span of your system.

Would you please compare that to Vdimm.
Are we talking about 2.77V being OK but 2.90V (max) would be pushing it for people that think that 1.9x Vcore is too high.


+ a specific q:
What is the lowest 80%x19x FSB that would be better than 75%x204 FSB in your opinion.

 

[hitechjb1]

If 75% of 204 is highest the memory can do, which equates to 153 MHz memory. Then that would put highest FSB at 153 / 0.8 = 191 MHz using the 80% ratio.

For the fine tuning of FSB, memory and CPU within a few MHz, the best way to decide which is better is to use Sandra to evaluate them.

As far as Vcore and Vdimm level, if the gain is not practically noticeable, say under 5%, I would rather keep a lower voltage to within your comfort zone for that 3-5% performance, unless your are trying to get a % or two for a benchmark competition.

 

[altec]

As far as Vcore and Vdimm level, if the gain is not practically noticeable, say under 5%, I would rather keep a lower voltage to within your comfort zone for that 3-5% performance, unless your are trying to get a % or two for a benchmark competition.

Very good statement. I run my vdimm at 2.9v (in BIOS) actually 3.0v, but this is comfortable for me since the memory I am using seems to thrive on higher voltages. The performance gain will be negligable for those extra Mhz, and if you do not feel comfortable with the voltage increase that you will need to use, It is not worth it.

 

[altec]

I added what nForce2 motherboards do not have the PCI lock option...at the request of another member.



Any more suggestions?

 

[RedDawg41]

where did you add this at? about the nforce2 non-pci-lock boars?
sorry for the late q's.

 

[altec]

Currently the nForce2 motherboards are the best because they offer a lot of features like the PCI lock that so many overclockers are enjoying at the moment, since they can reach FSB speeds of 200Mhz or higher. PCI lock basically locks the PCI bus speed at 33Mhz so that you will not have to use dividers and worry about your PCI bus speed causing problems like hard drive corruption and other known problems that come along with running your PCI bus too far out of spec. My preference in the nForce2 boards that are out right now are the Abit NF7-S Revision 2, the Epox 8RDA+, the Chaintech Zenith, and the Epox 8RDA3+. All of these board have confirmed PCI locks along with the Asus A7N8X. The nForce2 motherboards that do not have a PCI lock are the motherboards that are manufactured by MSI, Gigabyte, and Leadtek. They all seem like a good deal, but stay away from them, if you are going to spend the money on a motherboard with the nForce2 chipset, you will want PCI/AGP lock...at least.

Right there.

 

[modenaf1]

geez this guide is huge!!! but packed with info.

its funny, i was helping someone via PM and i recomended this and he stoped PMing me lol. either he fryed his chip and cant post or this guide is so gosh darn good there was no more need for my assistance

 

[RedDawg41]

Thanks again, altec. Your time and effort into this guide, along with Hitech as well as many others are greatly appreciated by myself an the rest of the OC'ers here. Great job.

 

[altec]

Thanks again, altec. Your time and effort into this guide, along with Hitech as well as many others are greatly appreciated by myself an the rest of the OC'ers here. Great job.

Well thank you. I leaned as much if not more than the average n00b that you see posting around on a regular basis, so I figure I should try to give back the knowledge that I have gotten...even if it isn't that much.

 

[RedDawg41]

bumb it.

 

[altec]

I added a link to BenchmarkHQ...they have tons of apps, including a lot of stress testers, CPU indenification programs, and benchmarking software. Definatley worth a look.

 

[RedDawg41]

bumb it

 

[sHape oF gReY]

BUMP this up where everyone can see it

 

[RedDawg41]

bumb it

 

[Jarhead7236]

more bumping....

 

[altec]

Thanks to this thread: http://forum.oc-forums.com/vb/showthread.php?s=&threadid=216091 I updated the information about the nForce2 motherboards and PCI lock. The issue is still not resolved, so if any more concrete evidence comes in, be sure to let me know so I can fix the guide accordingly.

 

[RedDawg41]

bumb it

 

[RedDawg41]

Bumb it