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 - Tuesday, September 8, 2009 - link
Anyone who buys a $1000 CPU has more money than brains. If you wait six months you can buy a newer budget processor for about 1/15 of the cost, overclock it and obtain the same result. I would think that $925 would be more valuable to someone with sense than bragging rights for six months. I was taught that when people brag they are vain morons. A person's value should not be estimated by the stuff they have, but by the choices they make. We all get a lot in life, it's what you do with it that sets you apart. Unfortunately our society is ruled by greed and capitalism. I choose to speak against that. If you have a problem with that, I suggest you take it up with the greedy capitalist complaint department. They don't care either.max347 - Wednesday, September 9, 2009 - link
Hmm, it would seem to me that someone who has $1k to spend on a cpu probably has "alot of brains", hence the better-than-average financial position, enabling the purchase in the first place.Also, you equate greed to capitalism. This is clearly false. People get what they work for in a capitalist society. I am not saying it is perfect, though what would be a better alternative? People are not going to be financially equal, as some work harder than others. To dispute this would demonstrate a lack of experience...to say the least.
Someone chooses to get the best. It's their money, their choice. But you're right, you should probably call them a greedy capitalist.
fullcooler - Wednesday, September 9, 2009 - link
wow, you said that way calmer than I would have. very classy reply to a young leftist. perhaps when obama passes the "free $1000 cpu's for lazy punk leftists" plan, you and I can pay for his cpu,and he wont be a sellout to the man by working for it.imaheadcase - Tuesday, September 8, 2009 - link
I hate people who used that phrase "Has more money than brains". Doesn't it stand to reason, they have brains..if they have more money than you to buy the CPU... lolJNo - Tuesday, September 8, 2009 - link
Not necessarily - they might have inherited the money for example.Maybe you have more money than brains too...
JonnyDough - Tuesday, September 8, 2009 - link
Yep. These people sound like they have no idea how to be frugal with money. It's ok though, a fool and his money are soon parted.lyeoh - Thursday, September 10, 2009 - link
Stop doing that ok?If you discourage too many rich/stupid people from buying the bleeding edge stuff it just makes it harder for the rest of us.
Poor folks like me need those rich guys to rush out and buy the expensive CPUs (and GPUs etc) and work all the bugs out, get the production line ramped up etc.
Then 6-12 months later we have good and cheap stuff to buy.
The best CPU costs way less than an expensive house anyway, so it's not like he's going to cause some sort of nation wide or global financial crisis.
VaultDweller - Tuesday, September 8, 2009 - link
Maybe they don't know how to be frugal with money.Maybe they don't NEED to be frugal with money.
Sure, a fool and his money are soon parted - but so is a brilliant rich man who has more money than he needs.
niva - Tuesday, September 8, 2009 - link
I disagree with your first statement. There are people who simply want the best/fastest and will pay the money for it. Only in the last 3 or 4 years has top of the line performance become relevant only for gaming. A few years ago all sorts of pros needed the fastest they can get their hands on and purchases like $1k per CPU were actually justified.Now just because you can't afford a 1k CPU and never have been, doesn't mean people who buy such things are morons. Same goes for buying a Ferrari by the way. Quit being a jealous putz, thanks!
JonnyDough - Tuesday, September 8, 2009 - link
When you compare value ratios, yes. A $1000 CPU is soon worth about $75. A Ferrari sold as parts is worth about 1/15 of the price also. I didn't think I'd have to spell it out for you.