The Sandy Bridge Preview
by Anand Lal Shimpi on August 27, 2010 2:38 PM ESTA New Architecture
This is a first. Usually when we go into these performance previews we’re aware of the architecture we’re reviewing, all we’re missing are the intimate details of how well it performs. This was the case for Conroe, Nehalem and Lynnfield (we sat Westmere out until final hardware was ready). Sandy Bridge, is a different story entirely.
Here’s what we do know.
Sandy Bridge is a 32nm CPU with an on-die GPU. While Clarkdale/Arrandale have a 45nm GPU on package, Sandy Bridge moves the GPU transistors on die. Not only is the GPU on die but it shares the L3 cache of the CPU.
There are two different GPU configurations, referred to internally as 1 core or 2 cores. A single GPU core in this case refers to 6 EUs, Intel’s graphics processor equivalent (NVIDIA would call them CUDA cores). Sandy Bridge will be offered in configurations with 6 or 12 EUs.
While the numbers may not sound like much, the Sandy Bridge GPU is significantly redesigned compared to what’s out currently. Intel already announced a ~2x performance improvement compared to Clarkdale/Arrandale, and I can say that after testing Sandy Bridge Intel has been able to achieve at least that.
Both the CPU and GPU on SB will be able to turbo independently of one another. If you’re playing a game that uses more GPU than CPU, the CPU may run at stock speed (or lower) and the GPU can use the additional thermal headroom to clock up. The same applies in reverse if you’re running something computationally intensive.
On the CPU side little is known about the execution pipeline. Sandy Bridge enables support for AVX instructions, just like Bulldozer. The CPU will also have dedicated hardware video transcoding hardware to fend off advances by GPUs in the transcoding space.
Caches remain mostly unchanged. The L1 cache is still 64KB (32KB instruction + 32KB data) and the L2 is still a low latency 256KB. I measured both as still 4 and 10 cycles respectively. The L3 cache has changed however.
Only the Core i7 2600 has an 8MB L3 cache, the 2400, 2500 and 2600 have a 6MB L3 and the 2100 has a 3MB L3. The L3 size should matter more with Sandy Bridge due to the fact that it’s shared by the GPU in those cases where the integrated graphics is active. I am a bit puzzled why Intel strayed from the steadfast 2MB L3 per core Nehalem’s lead architect wanted to commit to. I guess I’ll find out more from him at IDF :)
The other change appears to either be L3 cache latency or prefetcher aggressiveness, or both. Although most third party tools don’t accurately measure L3 latency they can usually give you a rough idea of latency changes between similar architectures. In this case I turned to cachemem which reported Sandy Bridge’s L3 latency as 26 cycles, down from ~35 in Lynnfield (Lynnfield’s actual L3 latency is 42 clocks).
As I mentioned before, I’m not sure whether this is the result of a lower latency L3 cache or more aggressive prefetchers, or both. I had limited time with the system and was unfortunately unable to do much more.
And that’s about it. I can fit everything I know about Sandy Bridge onto a single page and even then it’s not telling us much. We’ll certainly find out more at IDF next month. What I will say is this: Sandy Bridge is not a minor update. As you’ll soon see, the performance improvements the CPU will offer across the board will make most anyone want to upgrade.
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thewhat - Monday, August 30, 2010 - link
Because the 980X is a 6 core and the 950 is a 4 core!It doesn't make sense to compare a 6 core to a 4 core when there's an $800 price difference.
A 1366 4 core (preferably at the same CPU speed) would make much more sense to see the differences in various architectures/sockets.
SteelCity1981 - Monday, August 30, 2010 - link
ok and the diff in performance would be what now? if they are showing you the diff and how well the new 2 gen cpu's are to even a $1000 cpu what makes you think that the Core i7 950 which is slower in performance then a 980X would fair? I mean it's common logic that if the 2nd gens can run almost on par in many bench test with a 980X then obv it's going to run better then the Core i7 950's.kake - Sunday, August 29, 2010 - link
Damn you Intel! Damn you to hell!!I have been living with an AMD Athlon XP 1800+ since 2003ish. This was mostly because I liked the Soundstorm that did a very good Dolby Digital Live output. For the last eight months I've been having to run it at about 2/3rds speed because all the caps on the motherboard burst, and it ran at 80C all the time. The GPU fan died and I wired a 80mm fan on top of it, but it had overheated once too often to do any 3D work. The DVD burner wouldn't read or write, the DVD reader wouldn't open except under duress. The SATA bus started to scramble any data read or written through it, the second LAN port (the good one) died, and the USB would usually demand a musical chairs routine with the mouse and keyboard to get them to work.
So last week I bought all the bits and built a very reasonably priced (370 with shipping and tax) i3-530 based HTPC. I've never seen anything so gorgeous as the first time I played Avatar in 1080p on the plasma.
And now you tell me all this?
Damn you Intel, I'm sick of progress.
juampavalverde - Sunday, August 29, 2010 - link
There is a technological reason to bury 2 sockets that are still alive? they are screaming performance yet! i dont get what intel wants with this behavior, ¿Hate from the IT sector? i love the performance, but it is designed in a so closed and trickery way, and completely dropping two nice and stablished platforms, this thing wants to be hated. I hope amd destroys this crazy ideas of intel with llano oem sales, even being inferior in cpu performance.Googer - Monday, August 30, 2010 - link
What exactly does a Lifestyle processor do?mino - Monday, August 30, 2010 - link
Probably cuts your hair while playing Crisis :)Googer - Monday, August 30, 2010 - link
More like it shops for a convertible for you while you worry about your hair loss in your mid life Crysis.Googer - Monday, August 30, 2010 - link
More like it shops for a convertible for you while you worry about your hair loss in your mid life Crysis.Googer - Monday, August 30, 2010 - link
I understand what the difference between unlocked, regular, and power saving CPUs are. But what exactly does Intel mean by a Lifestyle processor? How is it different from the others? What exactly is a "Lifestyle CPU"?zepi - Monday, August 30, 2010 - link
What does the mystical "load power" mean? Does it mean running Prime95, Furmark, both or even something "real world" like Starcraft 2?