8GB 1066 DDR2...the rules

[Tony]

I see a few looking to run 8GB DDR2 1066, fact is its really hard to do, I can on occasion be dialled in with a ton of bios tweaking BUT it is so CPU dependent its unreal.

CPU dependent? Yes...remember the memory controller is on the CPU.

Its also dependent on the motherboard...signalling and crosstalk are the issue here, a board has to be built to do 1066 with 8GB and the fat is most are built to run 2 slots only at this speed.

So what do you do?

Well most of the bios files on boards now have an option to change the CPU-NB multiplier, OR you can lower the CPU multiplier and push up the HTT bus speed to increase the CPU-NB clock...this has a massive effect on performance.

keeping CPU at stock speed, increasing the CPU-NB multi to set the vclock at 2.6GHZ is like running ram at 1200+ MHZ with the ram actually running 800MHZ and is usually very easy to do.

AMD CPU's don't need masses of read bandwidth, they need fast access along side fast write and copy speed...you can do this by clocking around 850 to 900MHZ with tighter timings and push up the CPU-NB clock...

Keep this in mind if you have issues at 1066, you may actually be choosing the slower option.

[dinub1]

I see a few looking to run 8GB DDR2 1066, fact is its really hard to do, I can on occasion be dealing in with a ton of bios tweaking BUT it is so CPU dependent its unreal.

CPU dependent? Yes...remember the memory controller is on the CPU.

Its also dependent on the motherboard...signalling and crosstalk are the issue here, a board has to be built to do 1066 with 8GB, but the fact is most are built to run 2 slots only at this speed.

So what do you do?

Well most of the bios files on boards now have an option to change the CPU-NB multiplier, OR you can lower the CPU multiplier and push up the HTT bus speed to increase the CPU-NB clock...this has a massive effect on performance.

keeping CPU at stock speed, increasing the CPU-NB multi to set the vclock at 2.6GHZ is like running ram at 1200+ MHZ with the ram actually running 800MHZ and is usually very easy to do.

AMD CPU's don't need masses of read bandwidth, they need fast access along side fast write and copy speed...you can do this by clocking around 850 to 900MHZ with tighter timings and push up the CPU-NB clock...

Keep this in mind if you have issues at 1066, tyou may actually be choosing the slower option.

Couple of questions for you:
1. How an user can know if a motherboard is designed to support 8 GB of RAM at 1066 or only 4 GB (2 sticks)? . For example MSI DKA790GX states it supports up to 8 GB of RAM (no mention of the speed).
2. in an different post you recommend for 1066 MHz but DDR2 800 MHZ chips, user should use CPU-NB to 2200 Mhz. Now do you recommend to boost the CPU-NB to 2600 MHz but keep RAM speed to "800" (FSB/DRAM 1:2)? would this allow to run 8 GB of DDR2-800 RAM at 1066 MHz (2 x 533)? Pls. explain.
3. Clocking the RAM around 850-900 MHz with tighter timings? Mind to specify values? Is that tighter than 5-5-5-18?
How do you discretely/independently clock RAM itself (over 800), while keeping CPU clock nominal? Do you refer to increasing the CPU clock accordingly?

I am currently running 8 GB at 800 Mhz all on auto, quite stable...
In my experience, it looks like 2 X 2 GB setup at 800 MHz with CMD=1T, they appear running noticeably faster than the same pair running at 1066 CMD=2T.
Would I get a speed benefit if I succeed running them at 1066, with the tweaking you recommended? I doubt it. Pls. advise. Thanks.

[dinub1]

Noting that Tony has no time to answer, has nothing to say A busy fellah....

So... I did some experiments. Meanwhile I have a new PC case, an Antec P-182. and a Zalman 9700 blah blah (110 mm dia. fan) copper cooler.
These are the last settings: CPU multiplier set to 15.5X, basic CPU freq. 200 MHz (nominal), this renders 3100 MHz CPU speed (on a 3 GHz Phenom II CPU).
CPU-NB is set to 12 X (2400 MHz) and HTT is now 2000 MHz. CPU voltage adjusted up just slightly: 1.352 V. With 8 GB AMD compatible plats... system runs stable and quite fast.. All other voltage and settings on "auto". Memtest86 reports for some reason 1033 MHz speed (up from 1000 Mhz), though BIOS and CPU-ID still report 800 MHz.
CPU temp no more than 42 C under heavy load... ALL good

[Tony]

no chance of the NB hitting 2600?

[dinub1]

no chance of the NB hitting 2600?

Was this a question, or a suggestion? I did not try yet 2600 MHz for the NB... it might (run well)... as a rule, I do not try to overclock. I generally buy a system that is adequate to my needs. Overclocking is for people who try to push their system to the limit, but by doing this they may endanger their system and void warranty... As you may know a good system does not come cheap. So why wreck it for minimal benefits?

As I found out this Phenom II based system in conjunction with DDR2 PC-8500 RAM chips, is quite slow... this is with 2 X 2 GB sticks, running at 1066 Mhz. With 4 X 2 G we know it only supports 800 MHz... I refer as slow in regards to Windows XP.... with Vista, Windows 7 and Sidux 2009, with 8GB RAM, it runs much faster. So you (and I) found empirically that by boosting NB and HTT clock from nominal (auto) speeds, this system can run faster (actually data flows to and from RAM faster via the bus), and with no visible risks (that is no increased temp or voltages)...my CPU runs nominally at 200 MHz.. I slightly increased the CPU multiplier from (nominal) 15 X to 15.5 X. Now runs at 3.1 GHz instead of 3. I did not increase the basic CPU freq. But I found out that by increasing it over 205 MHz (basic clock) leads to instabilities and disk errors. It is true that I did not increase the CPU voltage.... I try not too... You need more heat dissipation for it. What for?

Now, if I increase the NB to 2600 (just change the multiplier to 13X instead of the current 12X) would I need a boost in NB voltage? I think it is currently 1.3 V. Should I increase it to say 1.35 or perhaps 1.4 V safely (as I saw in one of the posts here)? I have a well ventilated case (Antec P-182) and a decent CPU cooler (Zalman CPN9700 Cu). Pls. advise.

[dinub1]

no chance of the NB hitting 2600?

It does run stable with NB at 2600 MHz and voltage of 1.4 V. But CPU fan has to be set to max, as well as case fans... temp varies between 43 and 47 C under load... I am not sure I want this mode of operation.

Edit: Sometimes we have hot days in WA state... that was one of those days. Also I boosted the CPU multiplier to 16X, now it runs at 3.2 GHz. When ambient temps go down, say below 70F I can turn down the speed controller of the Zalman's fan to lower RPMs, that renders the PC much quieter and temps are lower (around 42 C Max). System works stable though.