Intel reveals more Sandy Bridge details at IDF

Intel reveals more Sandy Bridge details at IDF

Despite a massive GPU upgrade, Sandy Bridge still isn't able to take on mid-range discrete graphics cards

IDF 2010 Following on from our original news story, Intel has now started to confirm more technical details about the architecture of its forthcoming Sandy Bridge CPUs.

One of the most interesting of these is the new integrated GPU. For example, Intel has revealed that although it has a similar number of stream processors (or as Intel likes to call them 'execution units') to it's current-generation integrated GPU of existing Core i3 and i5 CPUs, the stream processors will have twice the throughput.

However, Intel reckons the biggest performance boost comes from switching the GPU from using system memory as its main repository of data to the Level 3 cache inside the CPU. Although this means that Intel has had to create all sorts of rules so that the CPU cores and GPU do not fight for access to the cache, as the cache delivers approximately four times the bandwidth of system memory, the system as a whole is much faster.

Intel described the process of creating these rules as 'thinking of the GPU as a fifth CPU core' not a separate unit. Using the cache has another benefit too: as the memory controller and system memory isn't being used it also saves a lot of power.

It's worth noting that most modern games will need considerably more texture memory than the Level 3 cache of a CPU can provide, so the Sandy Bridge GPU will still need to use system memory as well in these situations.

Intel reveals more Sandy Bridge details at IDF *Intel reveals more Sandy Bridge details at IDF

New Ring Interconnect

Probably the most interesting aspect of Sandy Bridge's design that Intel revealed today is its ring interconnect. Comprising 1,000 traces, this new bus, which delivers up to 96GB/sec per link, is based on the ring bus inside the Xeon 7500-series of CPUs and is used to connect the CPU cores, GPU, memory controller and Level 3 cache.

It was necessary for Intel to design this ring interconnect because the CPU cores and GPU in Sandy Bridge are built together on one die, which will use the 32nm manufacturing process. In contrast, existing Core i3 and Core i5 CPUs are built on a 32nm die and then patched together with a 45nm GPU. The ring interconnect is not only much faster than the existing QPI and DMI buses, but it should also enable Intel to ship variations on the basic Sandy Bridge design very quickly, such as models with different numbers of CPU cores.

CPU Upgrades

Intel also revealed some details about the core improvements inside the CPU portion of Sandy Bridge. The most notable of these is the ability of a Sandy Bridge CPU to load/store two addresses simultaneously, as opposed to the single address store of previous generation Intel processors.

Intel has also been talking about the enhanced form of Turbo Boost in Sandy Bridge. Specifically, unlike existing Bloomfield and Lynnfield CPUs, which can only overclock 1-2 CPU cores, Sandy Bridge CPUs can overclock all four cores simultaneously. What's more, the on-board GPU also supports Turbo Boost, although it can't overclock itself at the same time as the CPU cores. Confusingly, this means that Sandy Bridge CPUs can easily exceed their rated TDP, although Intel couldn't confirm what the point of having a TDP is if it can be exceeded.

Finally, Intel has been talking briefly about the new AVX (Advanced Vector Instructions). This is a new set of 256-bit instructions designed to enhance floating-point performance when handling media files, such as video and photo editing.

Beyond confirming that there will be dual- and quad-core models, Intel isn't talking clock speeds or model numbers for Sandy Bridge yet, although it did mention special low-power models with a TDP as low as 35W - much lower than most modern CPUs. Whether or not this low TDP will be exceeded via the new Turbo Boost remains to be seen.

Does Sandy Bridge sound like it's shaping up nicely? Share your thoughts in the forum.


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Hustler 14th September 2010, 13:24 Quote
What is the point of these intergrated Gfx cores on the CPU?.......what useful purpose do they serve?...

What market are Intel going after?. If they are giving you inbuilt Gfx, how are they taking market share away from Nvidia/AMD?.....

Those who need extra Gfx grunt, will still buy a dedicated Gfx card anyway.......will the inbuilt Gfx cores be able to be used as an additional benefit to a dedicated card, or are they bypassed once you add a dedicated Gfx card?....
TWeaK 14th September 2010, 13:27 Quote
Sounds interesting. I doubt I'll be upgrading for a long time yet, but the 2x 8 lane PCI-E sounds good. Hopefully this will mean fewer boards with the second slot limited to 4 lanes.

As for the TDP, hopefully at the least Intel will release 'normal TDP's and a 'max TDP'. Don't know if that's likely but it would be better than having a single figure that isn't right half the time.
BlackMage23 14th September 2010, 13:39 Quote
Sounds like they will be for business PC's.
Mraedis 14th September 2010, 15:01 Quote
Originally Posted by Hustler
What is the point of these intergrated Gfx cores on the CPU?.......what useful purpose do they serve?...

Motherboards would not require GPU's anymore, the cooling of the CPU/GPU would be concentrated and the shared cache etc would mean less need of RAM.

Of course, you'd use this type of core for desktops that aren't meant for gaming or otherwise video-heavy tasks, such as simple office management and regular browsing.
TSR2 14th September 2010, 17:16 Quote
If all 4 cores can overclock simultaneously, surely that's basically SpeedStep on a per-core basis? After all, if everything's good, its simultaneously awful.
frontline 14th September 2010, 18:25 Quote
Saw a few perfomance figures for the integrated GPU recently and it looked quite impressive when compared to something like a 5450 dedicated card. Certainly a lot better than Intel's previous integrated efforts and probably makes the entry level cards costing around £35-£45 redundant.
Snips 14th September 2010, 22:04 Quote
Maybe online gaming in work is back on the menu boys and girls!
dangerman1337 15th September 2010, 11:56 Quote
I wonder if intel are going to annouce details of the die shirnk and its tick tock after 22nm?
schmidtbag 18th September 2010, 03:29 Quote
overall it seems to me that sandy bridge is just a few touch-ups to nehalem. its nice to hear their integrated video is improved but i still think amd's and nvidia's are going to be better. on top of that, you can use the integrated video of an amd or nvidia chipset and use a descrete video card to get more processing power for free. with intel, you get a worse integrated video that doesn't have a descrete card to merge with, but, you at least can do sli or crossfire.

overall i find a cpu with built-in video a bad idea for desktops. you end up paying more for something you're probably not going to use. its a great idea for mobile devices or mini itx boards, but for a full-blown desktop its just dumb. i'm not too sure i like the idea of intel using the l3 cache for video either. sure, it'll make a great performance difference for video but the cache is going to have to be large, and the whole purpose of cache is to have a SMALL amount of memory that is quick to access.
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