New Sandy Bridge Computer Help (Built - WOW!) - Page 4

Prime95 · 2011-01-16, 20:14

Quote:

Originally Posted by Flatlander

If overclocking is done purely by raising the multiplier, would there be any point in me getting fast DDR3? Is that overclockable too in some way?

Yes, memory can be overclocked. I have no benchmarks indicating what difference that might make.

lavalamp · 2011-01-16, 23:17

Quote:

Originally Posted by Flatlander

If overclocking is done purely by raising the multiplier, would there be any point in me getting fast DDR3? Is that overclockable too in some way?

If you have an unlocked CPU, go for it. Most aren't.

Intel and AMD like to charge a premium for the top end chips because they have an unlocked CPU multiplier, also they usually come with an X or "Black" in the name. They allow more freedom when overclocking, failing that, you have to overclock the system bus that the other clocks (memory, QPI/HyperTransport and for Intel CPUs Uncore) are based on.

The good news is that the other multipliers are unlocked, so you can keep the other clocks at roughly the same speed while overclocking the CPU (or you can raise them all a little too).

Note: When I say CPU multipliers are locked, I mean you can't raise them (except with Turbo mode on Intel CPUs), but you can lower them. Sometimes it is advantageous to have a lower multiplier, either because you are overclocking other components or because the system is more stable, even at the same frequency (ie: 19 * 200 vs 20 * 190). Some people believe that on Intel CPUs the odd multipliers are more stable, whether or not that's true I don't know.

James Heinrich · 2011-01-17, 12:43

Quote:

Originally Posted by lavalamp

If you have an unlocked CPU, go for it. Most aren't.

Note that SandyBridge has changed a large number of things (mostly in the direction of locking them down severely) for overclocking, so certainly read some overview reviews (e.g. like this) before purchasing, if that's your goal. The current generation of Intel processors with unlocked multipliers have a "K" suffix, as in i7-2600K, generally at around a 10% price premium to their locked equivalents (well worth it).

Someone recently submitted a SandyBridge benchmark to my site, so comparing a first-generation i7-920 (overclocked to 3.4GHz) to a new i7-2600 at 3.4GHz you can see the performance increase: on FFT sizes 2M-8M, Sandy Bridge gets 5.0-5.5GHz-days/day compared to 3.5-4.0GHz-days/day on the older i7. That's a notable jump (note: both running at same clock speed).

lavalamp · 2011-01-17, 14:17

Yes, I just found out earlier today that for the Sandy Bridge chips, the base clock sets everything else on the board too, SATA, PCIe, USB etc. So raising it even 2 or 3 MHz can cause widespread system instability.

I can see why they've done this, but at the same time, it absolutely sucks and I hope they change it back.

Flatlander · 2011-01-18, 16:55

Can I assume that any Prime95 speed increase due to new Sandy Bridge instructions will filter down to LLR.exe for k*b^n+-1?

rogue · 2011-01-18, 17:29

Quote:

Originally Posted by Flatlander

Can I assume that any Prime95 speed increase due to new Sandy Bridge instructions will filter down to LLR.exe for k*b^n+-1?

Yes. PFGW too.

CRGreathouse · 2011-01-18, 18:14

Quote:

Originally Posted by lavalamp

I can see why they've done this, but at the same time, it absolutely sucks and I hope they change it back.

...why?

lavalamp · 2011-01-18, 18:51

Quote:

Originally Posted by CRGreathouse

...why?

Because it has basically killed the good old past time of buying a cheap CPU and overclocking the hell out of it.

Now you have to buy a more expensive CPU that already has a high clock, meaning you only squeeze a few more MHz out of it before it reaches the limit.

Ken_g6 · 2011-01-18, 22:03

They have "K" versions of the CPUs that are multiplier-unlocked, so you can overclock them quite a bit. So far, the "K" versions aren't much more expensive than non-K versions ($20-30 at most). Personally, I think the ~$200 i5 2500K is a better bargain than the ~$300 i7 2600K. The main difference between them being that the higher-numbered chip has hyperthreading, which I imagine doesn't matter much except on Folding@Home.

lavalamp · 2011-01-18, 22:26

The price is low because so far Intel have only released the budget chips. When the higher end 6 and 8 core Sandy Bridge chips hit, I expect the price of the K chips to be nothing short of astronomical.

ET_ · 2011-01-19, 13:21

Quote:

Originally Posted by Ken_g6

They have "K" versions of the CPUs that are multiplier-unlocked, so you can overclock them quite a bit. So far, the "K" versions aren't much more expensive than non-K versions ($20-30 at most). Personally, I think the ~$200 i5 2500K is a better bargain than the ~$300 i7 2600K. The main difference between them being that the higher-numbered chip has hyperthreading, which I imagine doesn't matter much except on Folding@Home.

Can the i5-2500K chip be installed into a LGA1156 socket (now hosting an i5-750)?

Luigi

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2011-01-17, 14:17	#37
lavalamp Oct 2007 Manchester, UK 2515₈ Posts	Yes, I just found out earlier today that for the Sandy Bridge chips, the base clock sets everything else on the board too, SATA, PCIe, USB etc. So raising it even 2 or 3 MHz can cause widespread system instability. I can see why they've done this, but at the same time, it absolutely sucks and I hope they change it back.

2011-01-18, 16:55	#38
Flatlander I quite division it "Chris" Feb 2005 England 31×67 Posts	Can I assume that any Prime95 speed increase due to new Sandy Bridge instructions will filter down to LLR.exe for k*b^n+-1?

2011-01-18, 22:03	#42
Ken_g6 Jan 2005 Caught in a sieve 613₈ Posts	They have "K" versions of the CPUs that are multiplier-unlocked, so you can overclock them quite a bit. So far, the "K" versions aren't much more expensive than non-K versions ($20-30 at most). Personally, I think the ~$200 i5 2500K is a better bargain than the ~$300 i7 2600K. The main difference between them being that the higher-numbered chip has hyperthreading, which I imagine doesn't matter much except on Folding@Home.

2011-01-18, 22:26	#43
lavalamp Oct 2007 Manchester, UK 23×59 Posts	The price is low because so far Intel have only released the budget chips. When the higher end 6 and 8 core Sandy Bridge chips hit, I expect the price of the K chips to be nothing short of astronomical.