Intel Core i5, Core i7 800 Processors and P55 Express - HotHardware

Intel Core i5, Core i7 800 Processors and P55 Express

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For the purposes of this article, we obtained Core i5 750 and Core i7 870 processors. To get a glimpse of their inner-workings, we first fired up the latest version of CPU-Z and snapped a few images of the pertinent details.

    
Core i5 750 CPU-Z Processor Details


    
Core i7 870 CPU-Z Processor Details

Although the chips are quite similar, there are two major differences to point out. First, obviously, are their clock speeds. The Core i5 750's default clock speed is 2.66GHz, the Core i7 870's is 2.93GHz and both chips clock down to about 1.2GHz while idling to save power. The Core i7 750's default clock speed is a result of its stock 20x multiplier and 133MHz base clock frequency (20 x 133MHz = 2.66GHz). The Core i7 870's default clock speed is 2.93GHz, which is a result of its 22x multiplier and similar 133MHz base clock. The second image in each series above, however, shows each chip under a threaded workload, which results in higher frequencies. With Turbo Mode enabled, the Core i5 750 hums along at 2.8GHz, while the i7 870 is at 3.2GHz.

The second major difference is that the Core i7 800 series support Intel's HyperThreading technology, which allows each execution core to processor two-threads simultaneously. As a result, CPU-Z correctly reports that the Core i7 870 and i5 750 feature 4 cores, but that the higher-end i7 870 can process 8 threads, while the Core i5 750 is limited to 4.

Cache configurations on the processors are the same, with 4 x 32K, 8-way associative L1 data caches, 4 x 32K, 4-way associative L1 instruction caches, 4 x 256K 8-way associative L2 caches, and 8MB of 16-way associative L3 caches.

Overclocking The Core i5 and i7
Pedal To The Metal


Core i5 750 Overclocked To 3.9GHz


Core i7 870 Overclocked To 3.9GHz

We also set out to do a bit of overclocking with the new Core i5 and Core i7 800 series processors, and came away very impressed. We should point out that there are no "Extreme Edition" Core i5 and Core i7 800 series processors, hence they are all multiplier locked for higher values and cannot be manually manipulated upwards to increase clock speeds. The only way to manually increase their frequencies is to increase the base clock speed, which by default runs at 133MHz.

To overclock the Core i5 750 and Core i7 870, we used the stock Intel cooler and a Gigabyte P55-UD6 motherboard. We first increased each processor's voltage to 1.4v and then increased the base clock frequency until our test system was no longer stable. Turbo mode was disabled to prevent any unwanted frequency spikes, but we left HyperThreading enabled on the i7 870. In the end, both chips easily handled 3.9GHz, with the stock cooler.

At 3.9GHz, the chips idled at around 45'C and peaked at over 70'C under load, but they were completely stable. We were also able to boot into Windows at speeds of up to 4.1GHz, but no amount of tweaking with the stock cooler would keep the system stable. With more exotic cooling, however, we suspect stable 4GHz overclocks will be somewhat commonplace with these new chips.
 

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AMD is gonna be in trouble again.  Many people rightfully opted for a Phenom II 955 instead of an i7 920 because the performance wasn't much slower, but it cost much cheaper.  With the i5 750 priced similar to the 955 (and cheaper than the 965) once again AMD's entire lineup is gettled shuffled into the sub $200 market.  AMD still wins at a number of price points below that price, but it's a shame that AMD can't come out with something a little faster.  Still, good for the consumers who now have a really good CPU at around $200.  At least you can still go DDR2 (which is still cheaper) with the Phenom II line so you can still always build a cheaper system AMD style, but $200+ is now exclusively Intel.

Gaming is mostly my interest, so I'd like to see some high settings and resolutions benchmarks comparing the Phenom II 955 or 965 and the i5 750.  Low settings makes sure it is not GPU dependent, but I want to see GPU dependence too.  If say the 750 gets 33.8 and the 965 gets 32.2 (made up numbers) in Crysis at 1920x1200, then we can still say that AMD is "good enough" and can be noticably cheaper with the DDR2 route.  However, if the i5 still has a decisive advantage at the highest settings, showing that it can make a GPU really shine to its fullest, then we can say AMD is really toast at a price point above $170.

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News:
At $199, the Core i5 750 can easily be considered a hot new mainstream quad-core offering.

Except for the fact that, as I write this, NewEgg and TigerDirect are charging $209.


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Super Dave:

News:
At $199, the Core i5 750 can easily be considered a hot new mainstream quad-core offering.

Except for the fact that, as I write this, NewEgg and TigerDirect are charging $209.


NEWSFLASH: The price has dropped to $206.99!

 

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Yeah, pricing is weird. Amazon has the i7 860 for $356. Expect that to come down REAL quick, since Newegg has it for $300. That's better, but wasn't the MSRP on that one $285?

At this point I'm going to put my new system build on the back burner. It appears, though, that I can get better value out of an 860-based system than a 920; unless someone can prove that triple channel memory does way better than dual channel. As far as I can tell, that and the integrated Northbridge are the biggest differences.

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Well if you want to OC it there are some differences.  The integrated PCIe controller has it's power tied to the Uncore.  So you won't be getting those crazy 4Ghz OCs on stock voltages.  You have to crank up the juice.

The dual channel memory controller with DDR3 1333Mhz can fully handle three of the cores hitting at max output.  Only place you'll take a hit there is with high demand apps that use all your cores or in things that are extremely memory intensive. 

As a side note, all the comparisons of memory bandwidth and such between them that I have seen (except here) have had the 900 series using DDR3 1066Mhz memory.  But even using slower memory the tri channel (of course) has higher bandwidth.  And that gap just expands with higher speed memory.  However, only when running more than 1.5 cores per memory channel flat out or in extremely memory speed limited situations will you see an advantage from the tri-channel.  I have 12GiB in my system and normally see 8~10GiB of it used, but then I try to keep as much stuff in memory as possible (plus added the pair of SSD's in RAID0 for the stuff that couldn't be there).  Memory resident with high bandwidth (specially backed by SSDs) makes the whole system feel silky smooth.

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How does the turbo thing affect overclocking? I would think that would make for a bit more work. Having to test each core to see if each one can run at the high speed when they are the only one maxed out.

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Well, their turbo in the new chips goes up to 5 speed bins higher, compared to only 2 on the 900 series.  If your upping the juice and want to keep turbo mode on, then it is best to clock the 700 and 800 series to something that will net you 3.8~4Ghz with a 5 speed bin increase.  If you turn the turbo mode off (add up the volts), it looks like most sites are hitting 4~4.2Ghz.  Oh, both of the above are with a non-stock cooler.  Seems the stock cooler is not very good at OCing.

If you don't up the voltage, the highest I have seen was about 3.46Ghz.  That PCIe on die gets unstable and messes things up without the extra voltage.

As for the question about cooling it, any decent after market air cooler will work.  The stock cooler is not up to OCing with extra voltage though.

 

Cheers

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>The stock cooler is not up to OCing with extra voltage though.

Is it ever? ,)

 

Being a belt-and-suspenders sort, I'd go with overcooling rather than undercooling, even if I wasn't reaching for the skies as far as overclocking. $65 for a Thor's Hammer or Megahalems (not counting fans) is a small price to pay, and the new lines of water coolers look promising and competitive.

 

Still, I'd like to see a review site do some testing on the temperature range we can expect from the new chips.

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@InfinityzeN: That sounds well-ordered. What you said appears to support buying an 860 if your needs aren't too extreme-- and since I'm designing the new system to be a decent World of Warcraft rig at 1680x1050 resolution, "not too extreme" describes it well. Bob_on_the_cob also convinced me that I don't need a CrossfireX setup, though I'd buy a motherboard that has that capability, in case someday there's an advantage to running more than one graphics card for WoW.

 

I also wonder about the heat produced by the Lynnfield chips. I'm not a crazymad overclocker, but I'd try to get a little extra juice out of the processor. I'll be looking forward to reading about temperature testing of the new chips to see whether liquid cooling or a massive air cooler is required, or whether I can get away with a quieter solution.

 

But I'm definitely waiting for prices to stabilize.

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