Intel's Larrabee Architecture Disclosure: A Calculated First Move
by Anand Lal Shimpi & Derek Wilson on August 4, 2008 12:00 AM EST- Posted in
- GPUs
How Many Cores in a Larrabee?
Initial estimates put Larrabee at somewhere in the 16 to 32-core range, we figured 32-cores would be a sweetspot (not in the least because Intel's charts and graphs showed diminishing returns over 32 cores) but 24-cores would be more likely for an initial product. Intel however shared some data that made us question all of that.
Remember the design experiment? Intel was able to fit a 10-core Larrabee into the space of a Core 2 Duo die. Given the specs of the Core 2 Duo Intel used (4MB L2 cache), it appears to be a 65nm Conroe/Merom based Core 2 Duo - with a 143 mm^2 die size.
At 143 mm^2, Intel could fit 10 Larrabee-like cores so let's double that. Now we're at 286mm^2 (still smaller than GT200 and about the size of AMD's RV770) and 20-cores. Double that once more and we've got 40-cores and have a 572mm^2 die, virtually the same size as NVIDIA's GT200 but on a 65nm process.
The move to 45nm could scale as well as 50%, but chances are we'll see something closer to 60 - 70% of the die size simply by moving to 45nm (which is the node that Larrabee will be built on). Our 40-core Larrabee is now at ~370mm^2 on 45nm. If Intel wanted to push for a NVIDIA-like die size we could easily see a 64-core Larrabee at launch for the high end, with 24 or 32-core versions aiming at the mainstream. Update: One thing we did not consider here is power limitations. So while Intel may be able to produce a 64-core Larrabee with a GT200-like die-size, such a chip may exceed physical power limitations. It's far more likely that we'll see something in the 16 - 32 core range at 45nm due to power constraints rather than die size constraints.
This is all purely speculation but it's a discussion that was worth having publicly.
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Shinei - Monday, August 4, 2008 - link
Some competition might do nVidia good--if Larrabee manages to outperform nvidia, you know nvidia will go berserk and release another hammer like the NV40 after R3x0 spanked them for a year.Maybe we'll start seeing those price/performance gains we've been spoiled with until ATI/AMD decided to stop being competitive.
Overall, this can only mean good things, even if Larrabee itself ultimately fails.
Griswold - Monday, August 4, 2008 - link
Wake-up call dumbo. AMD just started to mop the floor with nvidias products as far as price/performance goes.watersb - Monday, August 4, 2008 - link
great article!You compare the Larrabee to a Core 2 duo - for SIMD instructions, you multiplied by a (hypothetical) 10 cores to show Larrabee at 160 SIMD instructions per clock (IPC). But you show non-vector IPC as 2.
For a 10-core Larrabee, shouldn't that be x10 as well? For 20 scalar IPC
Adamv1 - Monday, August 4, 2008 - link
I know Intel has been working on Ray Tracing and I'm really curious how this is going to fit into the picture.From what i remember Ray Tracing is a highly parallel and scales quite well with more cores and they were talking about introducing it on 8 core processors, it seems to me this would be a great platform to try it on.
SuperGee - Thursday, August 7, 2008 - link
How it fit's.GPU from ATI and nV are called HArdware renderers. Stil a lot of fixed funtion. Rops TMU blender rasterizer etc. And unified shader are on the evolution to get more general purpouse. But they aren't fully GP.
This larrabee a exotic X86 massive multi core. Will act as just like a Multicore CPU. But optimised for GPU task and deployed as GPU.
So iNTel use a Software renderer and wil first emulate DirectX/OpenGL on it with its drivers.
Like nv ATI is more HAL with as backup HEL
Where Larrabee is pure HEL. But it's parralel power wil boost Software method as it is just like a large bunch of X86 cores.
HEL wil runs fast, as if it was 'HAL' with LArrabee. Because the software computing power for such task are avaible with it.
What this means is that as a GFX engine developer you got full freedom if you going to use larrabee directly.
Like they say first with a DirectX/openGL driver. Later with also a CPU driver where it can be easy target directly. thus like GPGPU task. but larrabee could pop up as extra cores in windows.
This means, because whatever you do is like a software solution.
You can make a software rendere on Ratracing method, but also a Voxel engine could be done to. But this software rendere will be accelerated bij the larrabee massive multicore CPU with could do GPU stuf also very good. But will boost any software renderer. Offcourse it must be full optimised for larrabee to get the most out of it. using those vector units and X86 larrabee extention.
Novalogic could use this to, for there Voxel game engine back in the day's of PIII.
It could accelerate any software renderer wich depend heavily on parralel computing.
icrf - Monday, August 4, 2008 - link
Since I don't play many games anymore, that aspect of Larrabee doesn't interest me any more than making economies of scale so I can buy one cheap. I'm very interested in seeing how well something like POV-Ray or an H.264 encoder can be implemented, and what kind of speed increase it'd see. Sure, these things could be implemented on current GPUs through Cuda/CTM, but that's such an different kind of task, it's not at all quick or easy. If it's significantly simpler, we'd actually see software sooner that supports it.cyberserf - Monday, August 4, 2008 - link
one word: MATROXGuuts - Monday, August 4, 2008 - link
You're going to have to use more than one word, sorry... I have no idea what in this article has anything to do with Matrox.phaxmohdem - Monday, August 4, 2008 - link
What you mean you DON'T have a Parhelia card in your PC? WTF is wrong with you?TonyB - Monday, August 4, 2008 - link
but can it play crysis?!