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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Shadowmaster625 - Tuesday, September 8, 2009 - link
Intel releases yet another new socket type, offering negligible performance enhancements vs socket 775. Soon they will obsolete another socket type still in use. And this is a good thing? I'm still dealing with the fallout from the socket 478...DJMiggy - Tuesday, September 8, 2009 - link
Thanks! Some good info! Now to decide what to do...Rabman - Tuesday, September 8, 2009 - link
Full disclusre -- I work for AMD, my comments are my own and do not reflect my employer, etc.A clarification on Windows 7's Core Parking feature -- it doesn't actually "[look] at the performance penalty from migrating a thread from one core to another". Rather, Core Parking was designed as a power saving feature for multi-core server machines, and is only enabled on Windows 7 client SKUs where HT is present (I won't get into specifics as to why this decision was made). The side benefit for processors with HT is that the hyperthreads can be parked so the Windows scheduler will spread threads across the "real" cores first, resulting in better performance characteristics.
rbbot - Tuesday, September 8, 2009 - link
That implies that it would have a negative effect on the chances of turbo mode engaging. On other OS, pure random chance would sometimes assign a waking thread to the hyper-core of the one already executing at full pelt. However, this means that on Windows 7, core parking prevents this happening and always wakes a 2nd core for the 2nd thread.puffpio - Tuesday, September 8, 2009 - link
If you disable turbo mode, will the individual cores still power down when unused?Take the 860 for example. With turbo mode enabled you get these overclocked speeds:
3C/4C Active: 3.54GHz
2C Active: 3.85GHz
1C Active: 4.00GHz
but with turbo mode disabled you get 3.99GHz at 1/2/3/4 cores active.
If the cores are still able to be powered down w/ turbo mode disabled, it would seem that would give you the best performance at any core activity level.
Comdrpopnfresh - Tuesday, September 8, 2009 - link
Specifically; power consumption, efficiency, and productivity/performance. On the consumer scale though- obviously with single-cpu boards benches geared towards commercial use would be droll.AFUMCBill - Tuesday, September 8, 2009 - link
Great Review.You mentioned the rising popularity of the uATX platform.
I would guess this is related to the rising popularity of laptops.
Except you can't find anything close to the performance of a Core i7 or i5 processor in a laptop form factor at anything remotely resembling a reasonable price - as in thousands and thousands of dollars extra. So people are headed to the uATX platform and the small(er) LAN party type boxes to get mobile performace. In my case I would like to be able to load high bitrate (25 Mbps and up) MPEG2 and MPEG4 footage into my video editor and have at it. My Q6600 handles the MPEG2 fine, but not the MPEG4 (AVCHD).
Found the Core i7 860 available at MicroCenter for $229.99 USD.
For me to make the buy, the only thing that is missing is USB 3.0.
Next year is looking good...and prices are likely to be even lower then :-)
Peroxyde - Tuesday, September 8, 2009 - link
Just checked at Newegg. Is there any error on the price? The newer and more performance i5 750 costs $209. The Q9550 cost $219. That sounds illogical.AFUMCBill - Tuesday, September 8, 2009 - link
I think it's called having old stock that was purchased before the new announcements. Obviously the folks they are going to be selling to are ones who are updating the processor in an older 775 socket motherboard based system - which with the new announcements are now rapidly receding into the past.C'DaleRider - Tuesday, September 8, 2009 - link
Sucks to have to depend on Newegg for buying, esp. considering what MicroCenter is doing. $199 for the i7 920 while Newegg gouges at $279, or the i5 750 for $179.Newegg long ago ceased being the place for the best prices.