Clocking i7 975 - Corsair 2000 CAS8 or Gskill 1600 CAS6

Soldato
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Asking this for a mate.

He wants to clock his i975 on rampage ii extreme.

Leaving out price (after all he has a 975), which of the following 6gig kits should he get. Initially he wants to overclock in small stages, but eventually will watercool to 4ghz and beyond.

Corsair Dominator GT 2000mhz CAS 8 8 8 24

or

Gskill Trident 1600mhz CAS 6 7 6 18
I noted on gskills site, this memory has been qualified by them for use with his motherboard

Would 1600mhz be enough for even a 4ghz overclock.
When would he need 2000mhz ?
 
Soldato
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2000mhz will get marginally better benchmark scores. On an unlocked multiplier he'll never need 2ghz ram but he might want it.

I would say the corsair if getting 6gb, or the gskill if 12. Simply because the board probably wont run 12gb at 2000mhz, and he'll probably care less about the cas numbers being marginally higher than stock than about the speed being lower.

Were price irrelevant I'd still have bought 1600mhz c8 corsair, triple channel bandwidth on a single processor board is excessive enough without running the ram very fast as well. But that's just me.

One thing that might swing it, mips have a waterblock for corsair dominator. Screws into the top, no warranty damage. This is why I have (admittedly the slower) corsair ram rather than the competition.

Cheers
 
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Get the G Skill 1600c6. Anything much faster than say 1600mhz C6/7 RAM yields little gains in overall performance other than a few bench points.

Then again, if he is bench mad then buy the fastest RAM you can and a phase unit and push that mofo past 5GHz.
 

rjk

rjk

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ocz blade - best triple channel kit on the market [and i have used them all]
 
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Alternatively, there is a nice cheap kit of Crucial value RAM he could get

3GB @£55.19
6GB @£98.89

Seen it at around 2000MHz on a water cooled system and over 2500MHz on a system using phase cooling.

You might need a fan for these :D
 
Soldato
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Thanks lads for all the good advice.

Now can I ask a dumbass questiona as I will be the one clocking it and am new to i7 clocking.

According to this asus link, when clocking an extreme I can ignore BCLK and just whack up the multiplier to 30 to give 4ghz, all the time leaving the BCLK at stock.

http://vip.asus.com/forum/view.aspx...e&id=20081220191040237&page=1&SLanguage=en-us

1. Doesn't keeping the BCLK at stock and hitting 4ghz with multi only give worse performance than an i7 920 D0 which has the BCLK adjusted to hit the same 4ghz ? I am coming from socket 775, so I assume the BCLK is something akin to FSB speed in terms of calculating the final speed of the cpu.

2. Typically what is the safe range of cpu voltage operation for an extreme, and what should I expect to need to hit 4ghz. I know every chip is different, but just wondering if it's common to hit 4ghz at stock settings. And while I'm at it, what is stock ? Can I trust auto voltage and assume the asus board won't overvolt the cpu ?


3. By not touching BCLK for the time being, doesn this mean memory, uncore and qpi won't be influenced either ? Should these be left on auto ? Same with their associated voltages ? Should I always dial in 1.65v for memory if not running it at the specced 1600mhz or 2000mhz ?

4. Should I disable Turbo mode ?

5. My understanding is memory frequency is bclk x memory multiplier
so if I leave the bclk alone at 133mhz, I assume the memory multiplier will default to 8 or 10 (even using the Corsair 2000mhz stuff); giving me 1066 or 1333mhz. And the uncore will be twice that (2133 or 2666). From looking at the link above, the common multipliers keeping the bclk at stock 133 are 6 to 14, so doesn't this mean the fastest speed I could hit for 2000mhz cas8 memory would be 1866 (133x14), pushing the Uncore up to 3733 or if I used 1600mhz stuff, I could use a 12 multiplier for a 3200 uncore, and still avail of CAS 6 timings and run the memory at it's specced 1600mhz. Given all this, what voltages would I need to change to make this happen ? I know memory can't go over 1.65, but how low can it go ? And what other voltages need to change ? I can't help thinking I would get better performance using a lower multiplier (say 10), and hopefully using a 200mhz BCLK, or even 180mhz BCLK. Of course that means having to mess with other voltages.

6. What effect does XMP profiles have ? Does it clock the memory and all the other gubbings to do with the cpu automatically. Can it be trusted ?
 
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Soldato
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Epic questions. I can do a few.

1/ Yes. Higher multiplier at lower bsck is going to perform worse than higher bsck at the same clock. The difference might not be deemed significant but it is definitely there. The appeal to the extreme editions as I see it is running a bsck of 200, which is within the normal motherboard limits of 220 or so, and then whatever multiplier you can get to. You can also kill the dirty mess that is turbo, since you don't need that extra +1 multi. Something like 200x25 would be the one I'd shoot for, but you're not getting that on air and probably not on water.

2/. Most people take the vid range as safe. Up to 1.375V for you. I am scathing of this, just because Intel say they'll sell a chip which runs at this voltage does not mean it is the limit or that it is safe. Stock voltage depends on chip, I'd expect around 1.1V or so. Stock ram voltage is 1.5V, that's almost certainly going up to 1.66V (1.65V if the board lets you pick this). However you've asked what's safe.

A safe voltage is one which does not cause measurable deterioration during the lifespan of the product. However what is safe is a function of temperature. 1.5V at -50 degrees is probably fine, 1.5V at 120 degrees is likely to kill it. It depends on what you're cooling it with. Most people on air seem to be at 1.3V or lower, otherwise they cannot control the temperatures. I don't know what I'll run on, probably whatever keeps the processor below about 80 degrees or when I hit diminishing returns. Currently 1.2 or so for 4ghz [ I'm having temperature issues with the motherboard, so am going to have to cool that more competently before pushing further. I hope you're aiming fans at the mosfets.] It's personal choice really. I'm going to push mine relatively hard, because I think processors are harder than people give credit for. However I will not use load line calibration, were I doing so I'd set am much lower safe voltage. llc causes spikes of far above what is set in the bios and generally makes bugger all sense, it's also violating intels voltage supply regulations. All you get is the peace of mind of the voltage not going down with load.

3/ Pretty certain if you just change multi, everything else stays the same. QPI is probably going to need more voltage, its the analogue of P45 northbridge voltage. So more qpi voltage when clocks go up, when ram is pushed harder etc. I'm unsure as to what is considered safe, but as its on processor die putting it up makes things hotter, and a cold processor can probably take a lot more on the qpi.

4/Yes. I'm disabling it on a 920 because I don't want the board changing the multiplier around. Were I using speed step I'd be more inclined to have it on. However you have an extreme chip, so have whatever multiplier you want without messing around with turbo. Definitely turn it off.

5/I had this argument with someone a while ago. I agree with you. 2000mhz is only usable at higher bsck than 133. The person who'd bought it refused to overclock and thought it was unreasonable that his ram was running below stock. The main issue is that you hit problems around the ucore > 4000 mark where stability just goes to hell. The limit depends on chip and probably on temperature, and imposes a general restriction on how high you can push bsck or ram. Hence I run 1600mhz ram, there's one multiplier lower to fall back on if needed and otherwise 200 x 20 @ 1600mhz ram are just really nice numbers for 24/7 if I can't get any higher.

Intel say the ram voltage cant go over 1.65V or you'll hurt the processor. The ram companies are a bit close lipped but I think are of the opinion that their ram will be fine well over this. Several people running at 1.7, a few at 1.8V. There's a thread on xtreme about dead processors, some had mad voltages running through them and were doing fine.

XMP profiles seem to be the same as profiles were before. I'm a bit unsure on this one, but then I set timings manually so haven't really looked into it. Reminds me that auto voltage is not a good idea on the processor, think I forgot to say that earlier.

That's my best shot. Pretty certain on all of the above, but think I've missed parts of your post. I'd like to know how you're cooling this system, if it's air I recommend buying cheaper ram or a cheaper processor and putting it on water. Board as well

Think you're going to have fun :)
 
Soldato
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Thanks ever so much for all that. Alot to digest.

I'm building a system from scratch for me as well as for a mate so both in the same boat really. Going to be using a Corsair H50 for cooling the cpu. Eventually will move to water. 1st time looking at i7 to be honest.

I have described my build here. Nothing out of this world.
http://forums.overclockers.co.uk/showthread.php?t=18061352

Most importantly I will be looking for stability. Then will gradually overclock. Last time I was seriously into overclocking was pre core2duo days.

thanks again
 
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