Intel's Core i7 870 & i5 750, Lynnfield: Harder, Better, Faster Stronger
by Anand Lal Shimpi on September 8, 2009 12:00 AM EST- Posted in
- CPUs
Multi-GPU SLI/CF Scaling: Lynnfield's Blemish
When running in single-GPU mode, the on-die PCIe controller maintains a full x16 connection to your graphics card:
Hooray.
In multi-GPU mode, the 16 lanes have to be split in two:
To support this the motherboard maker needs to put down ~$3 worth of PCIe switches:
Now SLI and Crossfire can work, although the motherboard maker also needs to pay NVIDIA a few dollars to legally make SLI work.
The question is do you give up any performance when going with Lynnfield's 2 x8 implementation vs. Bloomfield/X58's 2 x16 PCIe configuration? In short, at the high end, yes.
I looked at scaling in two games that scaled the best with multiple GPUs: Crysis Warhead and FarCry 2. I ran all settings at their max, resolution at 2560 x 1600 but with no AA.
I included two multi-GPU configurations. A pair of GeForce GTX 275s from EVGA for NVIDIA:
A coupla GPUs and a few cores can go a long way
And to really stress things, I looked at two Radeon HD 4870 X2s from Sapphire. Note that each card has two GPUs so this is actually a 4-GPU configuration, enough to really stress a PCIe x8 interface.
First, the dual-GPU results from NVIDIA.
| NVIDIA GeForce GTX 275 | Crysis Warhead (ambush) | Crysis Warhead (avalanche) | Crysis Warhead (frost) | FarCry 2 Playback Demo Action |
| Intel Core i7 975 (X58) - 1GPU | 20.8 fps | 23.0 fps | 21.4 fps | 41.0 fps |
| Intel Core i7 870 (P55) 1GPU | 20.8 fps | 22.9 fps | 21.5 fps | 40.5 fps |
| Intel Core i7 975 (X58) - 2GPUs | 38.4 fps | 42.3 fps | 38.0 fps | 73.2 fps |
| Intel Core i7 870 (P55) 2GPUs | 38.0 fps | 41.9 fps | 37.4 fps | 65.9 fps |
The important data is in the next table. What you're looking at here is the % speedup from one to two GPUs on X58 vs. P55. In theory, X58 should have higher percentages because each GPU gets 16 PCIe lanes while Lynnfield only provides 8 per GPU.
| GTX 275 -> GTX 275 SLI Scaling | Crysis Warhead (ambush) | Crysis Warhead (avalanche) | Crysis Warhead (frost) | FarCry 2 Playback Demo Action |
| Intel Core i7 975 (X58) | 84.6% | 83.9% | 77.6% | 78.5% |
| Intel Core i7 870 (P55) | 82.7% | 83.0% | 74.0% | 62.7% |
For the most part, the X58 platform was only a couple of percent better in scaling. That changes with the Far Cry 2 results where X58 manages to get 78% scaling while P55 only delivers 62%. It's clearly not the most common case, but it can happen. If you're going to be building a high-end dual-GPU setup, X58 is probably worth it.
Next, the quad-GPU results from AMD:
| AMD Radeon HD 4870 X2 | Crysis Warhead (ambush) | Crysis Warhead (avalanche) | Crysis Warhead (frost) | FarCry 2 Playback Demo Action |
| Intel Core i7 975 (X58) - 2GPUs | 25.8 fps | 31.3 fps | 27.0 fps | 70.9 fps |
| Intel Core i7 870 (P55) 2GPUs | 24.4 fps | 31.1 fps | 26.6 fps | 71.4 fps |
| Intel Core i7 975 (X58) - 4GPUs | 27.0 fps | 57.4 fps | 47.9 fps | 117.9 fps |
| Intel Core i7 870 (P55) 4GPUs | 24.2 fps | 50.0 fps | 36.5 fps | 116 fps |
Again, what we really care about is the scaling. Note how single GPU performance is identical between Bloomfield/Lynnfield, but multi-GPU performance is noticeably lower on Lynnfield. This isn't going to be good:
| 4870 X2 -> 4870 X2 CF Scaling | Crysis Warhead (ambush) | Crysis Warhead (avalanche) | Crysis Warhead (frost) | FarCry 2 Playback Demo Action |
| Intel Core i7 975 (X58) | 4.7% | 83.4% | 77.4% | 66.3% |
| Intel Core i7 870 (P55) | -1.0% | 60.8% | 37.2% | 62.5% |
Ouch. Maybe Lynnfield is human after all. Almost across the board the quad-GPU results significantly favor X58. It makes sense given how data hungry these GPUs are. Again, the conclusion here is that for a high end multi-GPU setup you'll want to go with X58/Bloomfield.
A Quick Look at GPU Limited Gaming
With all of our CPU reviews we try to strike a balance between CPU and GPU limited game tests in order to show which CPU is truly faster at running game code. In fact all of our CPU tests are designed to figure out which CPUs are best at a number of tasks.
However, the vast majority of games today will be limited by whatever graphics card you have in your system. The performance differences we talked about a earlier will all but disappear in these scenarios. Allow me to present data from Crysis Warhead running at 2560 x 1600 with maximum quality settings:
| NVIDIA GeForce GTX 275 | Crysis Warhead (ambush) | Crysis Warhead (avalanche) | Crysis Warhead (frost) |
| Intel Core i7 975 | 20.8 fps | 23.0 fps | 21.4 fps |
| Intel Core i7 870 | 20.8 fps | 22.9 fps | 21.5 fps |
| AMD Phenom II X4 965 BE | 20.9 fps | 23.0 fps | 21.5 fps |
They're all the same. This shouldn't come as a surprise to anyone, it's always been the case. Any CPU near the high end, when faced with the same GPU bottleneck, will perform the same in game.
Now that doesn't mean you should ignore performance data and buy a slower CPU. You always want to purchase the best performing CPU you can at any given pricepoint. It'll ensure that regardless of the CPU/GPU balance in applications and games that you're always left with the best performance possible.
The Test
| Motherboard: | Intel DP55KG (Intel P55) Intel DX58SO (Intel X58) Intel DX48BT2 (Intel X48) Gigabyte GA-MA790FXT-UD5P (790FX) |
| Chipset: | Intel X48 Intel X58 Intel P55 AMD 790FX |
| Chipset Drivers: | Intel 9.1.1.1015 (Intel) AMD Catalyst 9.8 |
| Hard Disk: | Intel X25-M SSD (80GB) |
| Memory: | Qimonda DDR3-1066 4 x 1GB (7-7-7-20) Corsair DDR3-1333 4 x 1GB (7-7-7-20) Patriot Viper DDR3-1333 2 x 2GB (7-7-7-20) |
| Video Card: | eVGA GeForce GTX 280 |
| Video Drivers: | NVIDIA ForceWare 190.62 (Win764) NVIDIA ForceWare 180.43 (Vista64) NVIDIA ForceWare 178.24 (Vista32) |
| Desktop Resolution: | 1920 x 1200 |
| OS: | Windows Vista Ultimate 32-bit (for SYSMark) Windows Vista Ultimate 64-bit Windows 7 64-bit |
Turbo mode is enabled for the P55 and X58 platforms.
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Scheme - Tuesday, September 8, 2009 - link
Why is it assumed enthusiasts or technical users are only interested in overclocking? For me it's about balancing performance, temps, noise levels and power consumption, all with a reasonable cost of entry. All that considered Lynnfield seems to be a good platform.Ann3x - Tuesday, September 8, 2009 - link
Well the d0 can usually hit 3.8-4ghz on std voltages.So tbh temps dont really come into it. Anyone with a 920 should overclock it because there is really nothing to lose. No need to risk the cpu, negligible temperature increases, its all positive.
If you buy a 920 and dont overclock you either should have a very good reason or you dont know how to.
The 920 is a very meh processor at stock. The reason its so popular is its potential to overclock so easily and so highly not its stock speeds.
Scheme - Tuesday, September 8, 2009 - link
3.8-4ghz will involve more than what I'd consider to be 'negligible temperature increases'.Ann3x - Tuesday, September 8, 2009 - link
I can hit 4Ghz on air with stock voltage with a max load (10hrs of LinX) of 65C. Thats so far within the thermal limits of the CPU to be considered totally negligible. My results seem very typical for d0 920s.Enthusiast CPUs need to be treated (and reviewed) in context with their market. If some people are too stupid to see the potential of their mid range CPUs then Id at least expect a good site like anandtech to realise it and not act like stock is the only option.
There is a reason why 90% of X58 motherboards are marketed on their overclock and performance options.
erple2 - Tuesday, September 8, 2009 - link
I'm a bit more interested in relatively low power consumption, and stable (as in for 4 years) operation, not how many fractional increases in performance I can eke out of a CPU at potentially catastrophic failure rates through overclocking. However, I'm buying a CPU for it's solid performance, reliability (the i7's haven't been out long enough to make any judgement of it's long term reliability), and lower power consumption. Also, can you still claim RMA status on a broken CPU that was potentially damaged by overclocking? I haven't read any Intel literature to suggest that you can.I don't care at all about what you think I my goals with buying a CPU for are. Your class of "enthusiast" is really "the overclocking user", not the "enthusiast".
I suppose it would be more interesting to find out how many of the X58 purchasers actually overclock their CPUs (beyond what "turbo" buys you), and then make conclusions, rather than this handwaving "you're an idiot if you do something other than what I do" mentality that you are showing.
I'd also like to see how many of those "90% of X58 mobos marketed on their overclock and performance options" (reference please!) are actually sold vs. those that are cheaper, and not marketed on overclocking performance. Maybe that "other 10%" sells about 40-50% of the market. Do you have data to suggest otherwise?
Ann3x - Wednesday, September 9, 2009 - link
You really think you can damage a cpu by just increasing the clock? Wow.Only things that damage CPUs are overvolting (not needed for a decent OC on the i7) and high temps (usually linked directly to overvolting). The concept that an overclock at stock voltage could cause "catastrophic failure" is frankly laughable.
A sensible overclock will be no more or less stable than stock. The only people who actually risk system stability are the ones who overvolt and push the limits. For the record 3.8-4ghz is most definitely NOT pushing the limits.
Again ill say it. If youre buying an X58 motherboard you are PAYING for the ability to overclock. If you choose not to there is little - no point in the platform (with the possible exception of people who use very multi threaded apps). The proof in this point is actually staring you in the face in the i5/new i7, their design shows that intel realises the headroom they have in the architecture. The aggressive turbo mode of the i5/new i7 is proof that there is NO risk in overclocking within sensible limits at stock voltage.
In reality the main "huge leap forward" of the new platform is simply the acceptance of overclocking within intel.
That you choose to ignore the potential of your CPU is your own loss. Intel think its safe to overclock but hey, you know better right :). Im just surprised that anand chooses to for the most part ignore this and makes absurb attention grabbing statements instead of assessing the real merits of the 2 platforms. It really is a rose tinted glasses review but oh well. Keep your heads stuck in the sand.
yacoub - Tuesday, September 8, 2009 - link
Great article except it would have been REALLY nice to have the i7 860 data, given that's most likely the best bang-for-the-buck Lynnfield option and it probably makes MUCH more sense price-wise than going for the 870. It REALLY sucks not knowing where that chip slots in for all the tests you did.This is exactly the concern I listed when the polls were posted that asked which CPU we most wanted to see benchmarked. Clearly we want to see ALL THREE.
That said, it's nice to see Lynnfield is basically awesome, except in Crossfire/SLI which is about the LAST thing I could give a crap about. So really, this looks about perfect. (Only on page 14 though, but if it continues as it has to this point, I'm sold.) I just wish the 860 had been benchmarked.
Gary Key - Tuesday, September 8, 2009 - link
I have the 860 in the upcoming mb roundups. :)yacoub - Tuesday, September 8, 2009 - link
I knew there was a reason we all love us some Gary Key. \m/. :)529th - Tuesday, September 8, 2009 - link
I'm not sure what bios setting is Sleep State on the i7 9xx (1366) but for discussions sake, say C1E sleep state is disabled, as overclockers usually do this, does that negate the logical functioning of Turbo mode and run all cores at the max TDP & speed? So would a 1366 system be faster with turbo & C1E sleep state disabled? ...i'm not even sure if i'm asking that right.. i'm still reading up on the PCU and Turbo section