Intel's Sandy Bridge Architecture Exposed
by Anand Lal Shimpi on September 14, 2010 4:10 AM EST- Posted in
- CPUs
- Intel
- Sandy Bridge
New, More Aggressive Turbo
Lynnfield was the first Intel CPU to aggressively pursue the idea of dynamically increasing the core clock of active CPU cores while powering down idle cores. The idea is that if you have a 95W TDP for a quad-core CPU, but three of those four cores are idle, then you can increase the clock speed of the one active core until you hit that TDP limit.
In all current generation processors the assumption is that the CPU reaches that TDP immediately upon enabling turbo. In reality however, the CPU doesn’t heat up immediately - there’s a period of time where the CPU isn’t dissipating its full TDP - there’s a ramp.
Sandy Bridge takes advantage of this by allowing the PCU to turbo up active cores above TDP for short periods of time (up to 25 seconds). The PCU keeps track of available thermal budget while idle and spends it when CPU demand goes up. The longer the CPU remains idle, the more potential it has to ramp up above TDP later on. When a workload comes around, the CPU can turbo above its TDP and step down as the processor heats up, eventually settling down at its TDP.
While SNB can turbo up beyond its TDP, the PCU won’t allow the chip to exceed any reliability limits (similar to turbo today).
In addition to above-TDP-turbo, Sandy Bridge will also support more turbo bins than Nehalem/Westmere. Intel isn’t disclosing how much more turbo headroom we’ll have, but the additional bins are at least visible with multiple cores active. Current designs usually only turbo up one or two bins with all four cores active, I’d expect to see another bin or two there and possibly more in lighter load cases.
Both CPU and GPU turbo can work in tandem. Workloads that are more GPU bound running on SNB can result in the CPU cores clocking down and the GPU clocking up, while CPU bound tasks can drop the GPU frequency and increase CPU frequency.
Sandy Bridge as a whole is much more dynamic of a beast than anything that’s come before it.
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iwodo - Tuesday, September 14, 2010 - link
Many questions still not answered, may be Anand could found out for us.1. Were the GPU performance we saw from 6 EU or 12 EU?
2. Where is FMA ( Fused Multiply Add ) ? Will we see it in Ivy Bridge?
3. Can All software developers access the Decoding Engine? We could see many codec being optimized for playback on Intel Hardware Decoder, whether it is fully supported codec or partially supported codec.
4. Hardware Encoder? It is Full Hardware encoder? Free to use for Software Dev?
5. OpenCL not possible?
6. How many % die size is given to Graphics?
7. Gfx Drivers, will Intel commit more resources on drivers update? Or Will they open sources it?
Apart from Sandy Bridge, Looking forward for reports on USB 3.0 situations, LightPeak, Gen 3 SSD.
trivik12 - Tuesday, September 14, 2010 - link
1) I believe it was 12EU part.2) FMA will be introduced with Haswell(next tock). So we have to wait until early 2013 for that.
Foo999 - Tuesday, September 14, 2010 - link
> 2. Where is FMA ( Fused Multiply Add ) ? Will we see it in Ivy Bridge?You can check out the full current (and Ivy Bridge) AVX instructions in the AVX reference manual available from software.intel.com/en-us/avx/
spart - Tuesday, September 14, 2010 - link
1 , 6UE The 12 is only for laptops and high rangesgvaley - Tuesday, September 14, 2010 - link
So, was it playable, I mean Starcraft II?therealnickdanger - Tuesday, September 14, 2010 - link
Yeah, the caption said "310M vs Sandy Bridge" so I assume you could see the settings and frames per second. Details, man, details!!:)
Anand Lal Shimpi - Tuesday, September 14, 2010 - link
Yes, it was playable at medium quality settings. They only had the single player campaign running however.Take care,
Anand
Carleh - Tuesday, September 14, 2010 - link
With BCLK locked, where does that leave the motherboard manufacturers?I mean, what are they left to offer to enthusiasts, if the BCLK is locked? How are they going to differentiate an enthusiast-class motherboard from a mainstream one?
ssj4Gogeta - Tuesday, September 14, 2010 - link
Will they be locking the socket 2011 parts as well?Zoomer - Sunday, September 19, 2010 - link
Sell more bullbozer boards. I was all set to be ready to get a nice Sandy Bridge and overclock it to hell, but now I think I'll get a bulldozer instead.Sure there's the K, but it costs more. That kinda defeats the point, unless the aim is to get a high clk for epeen.