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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JonnyDough - Thursday, September 10, 2009 - link
Were you purposely reiterating my point? :DI don't think AMD ever much cared about what Intel was doing. In business class I was taught to keep an eye on a competitor but to really focus on what you are doing. I think AMD was planning their next move, and it had little to do with what Intel was doing or planned on doing, but rather the reaction of what Intel would do when they created Athlon and the next step to being a successful innovative company. Going graphics was just a logical step, since NVidia had no real competition in this space. They saw a market that was ruled by two giants, and decided to combine technology. I'm not so sure that Intel had the idea first. Don't forget, there are leaks in this industry, and people are getting paid to snitch.
tajmahal - Tuesday, September 8, 2009 - link
This is the first time i've ever seen an article written using wholesale x 1,000 prices. Is there any reason you didn't take the trouble to post actual retail pricing?JonnyDough - Tuesday, September 8, 2009 - link
He probably wrote this article prior to today and based it off Intel's pricing scheme...I would think you'd probably gather that. NewEgg is also not the only E-tailer/Retailer out there...ViRGE - Tuesday, September 8, 2009 - link
The last time I checked, those are the only prices Intel gives out. The actual retail prices are a combination of what the retailer paid (buy more, spend less) and whatever markup they add. Intel doesn't have an MSRP.tajmahal - Tuesday, September 8, 2009 - link
i5 750 = $210i7 860 = $300
i7 870 = $580
Just in case someone wants to buy just 1 instead of 1,000. Newegg prices
Gary Key - Tuesday, September 8, 2009 - link
"i5 750 = $210i7 860 = $300
i7 870 = $580
Just in case someone wants to buy just 1 instead of 1,000. Newegg prices "
Retail prices fluctuate greatly at launch. This is what I paid for our retail processors with tax mind you. ;)
i5 750 = $205
i7 860 = $306
i7 870 = $564
cycleback - Tuesday, September 8, 2009 - link
Could you post some Linpack and finite element code benchmarks. This would approximate a larger number of HPC workloads. I would really appreciate this as it is difficult to find these sorts of benchmarks. It would also really test the difference in memory bandwidth between Bloomfield and Lynfield.tacoburrito - Tuesday, September 8, 2009 - link
From the benchmarks, the i7 920 and the i5 seems to be even; each winning about half the benchmarks. If costs for both are the same (proc and mobo), I think I'd still go with the 920. Of course I can stop being a cheap bastard and spring for the i7 860.tacoburrito - Tuesday, September 8, 2009 - link
I also meant to add that it should just be a matter of time before Intel cut the prices of the 920.TA152H - Tuesday, September 8, 2009 - link
One thing that's obvious is, after reading this, that the esteemed reviewer modified his review in order to fulfill his preconceived ideas of what he wanted to say. It's really a terrible review.Most people know this site isn't technical, but still, I always thought it was unbiased. It's biased, big time, just not for a company. It's about making a review say what they want.
For example, I doubt Anand is really as stupid as he sounds in this article. LGA1366 has so many advantages, certainly he knows this. But why the idiotic remarks about asking why it exists?
Why did this review ignore the fact that most people here overclock? Why did it ignore that most people reading these reviews won't use DDR3 1066 memory? Did this site just try to become PC Magazine without the writing talent, and go stock? I think not. It was because they only wanted to give information that was consistent with their preconceived idea.
But, let's look closer. The memory controller on the Bloomfield is actually faster than the Lynnfield when using the same memory, even when running in dual channel mode. Why wasn't it mentioned here?
Why wasn't a clock normalized comparison between the LGA1366 processors and LGA1156 processors made, or even attempted, to get an idea of what the architecture changes accounted for? Strange that this very important data is missing? I think so.
Why weren't overclock processors compared? I mean, will anyone here buy an i7 920 and not overclock it? Probably not many. Since the only real advantage is the more aggressive turbo mode, this was what the article was based on. But, in reality, for readers here, it's not important, since people are going to overclock, and the i7 920 would wipe the floor up with the Lynnfields in the configuration that would be used. Why no mention of this?
There are better sites that have answered these questions. I used to like this site, but this review is another disappointment.
Let's be real though, it looks like the processor's horrible performance in the pre-release configuration is just a bad memory. It's not a bad part by any stretch, but it's hardly made the LGA1366 useless, or even the i7 920. The technical savvy will still opt for it in a lot of instances, since they will overclock it. If you have to recommend something for a friend that won't, these things are fine.
Another really stupid remark was how AMD processors would only make sense if they drop the price. Have you forgotten AMD processors are coupled with excellent IGPs? That's been the big selling point for a while, and this hasn't really changed that, too much. IGP platforms are really big in sales too, so, I'd agree with the premise that AMD probably should lower their prices a little, but not that they don't have advantages even where they are. The processors don't, but you can't get an Intel motherboard with the 790GX either. And if they come out with something better, as rumored, it's just going to give their platform another advantage to help counteract their horrible processors (yes, I agree they suck).