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Larrabee Based On a Bundle of Old Pentium Chips
Posted by
ScuttleMonkey
on Mon Jul 07, 2008 05:29 PM
from the making-old-new-again dept.
from the making-old-new-again dept.
arcticstoat writes "Intel's Pat Gelsinger recently revealed that Larrabee's 32 IA cores will in fact be based on Intel's ancient P54C architecture, which was last seen in the original Pentium chips, such as the Pentium 75, in the early 1990s. The chip will feature 32 of these cores, which will each feature a 512-bit wide SIMD (single input, multiple data) vector processing unit."
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Pentium 75? (Score:5, Funny)
Re:Pentium 75? (Score:5, Funny)
Making math errors at blazing speeds...
Parent
Re:Pentium 75? (Score:5, Funny)
Oh, don't worry about that. Games will just be more interesting. For example, that 3D monster you're trying to hack to death with a chainsaw will now suddenly shift to a different part of the screen... Or maybe you'll get a cool color-cycling effect from some incorrectly calculated values...
"Intel Graphics Inside--it's all in good fun!"
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Re:Pentium 75? (Score:5, Funny)
You mean my FPS will behave like World of Warcraft now? Wonderful!
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Re:Pentium 75? (Score:5, Informative)
I don't care if you're a C64 fanboi, Pentiums made mistakes. Apple had nothing do to with it. Read here [wikipedia.org].
And this also from the same source... "In June 1994, Intel engineers discovered a flaw in the floating-point math subsection of the Pentium microprocessor. Under certain data dependent conditions, low order bits of the result of floating-point division operations would be incorrect, an error that can quickly compound in floating-point operations to much larger errors in subsequent calculations. Intel corrected the error in a future chip revision, but nonetheless declined to disclose it."
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Re:Pentium 75? (Score:5, Funny)
Oh it performed them reliably.. just reliably wrong.
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What the hell is Larrabee? (Score:5, Insightful)
A little context might help. This isn't the Inquirer for god's sake.
Re:What the hell is Larrabee? (Score:5, Informative)
According to Wikipedia http://en.wikipedia.org/wiki/Larrabee_(GPU) [wikipedia.org]
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Re:What the hell is Larrabee? (Score:5, Insightful)
Parent
Re:What the hell is Larrabee? (Score:5, Insightful)
sorry for the drunken english
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Re:What the hell is Larrabee? (Score:5, Funny)
It's one of the larger cities in Wyoming. Get with it. ;)
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Re:What the hell is Larrabee? (Score:5, Funny)
It's one of the larger cities in Wyoming. Get with it. ;)
Only if you have a head cold.
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Manycore GPU (Score:5, Interesting)
Larrabee [wikipedia.org] is going to be Intel's next creation in the GPU world. A many core GPU which has the following peculiarities :
- fully compatible with x86 instruction set. (whereas other GPU use different architecture, and often instruction sets that aren't as much adapted to run general computing).
Thus, the Larrabee could *also* be used as a many core main processor (if popped into a quick path socket) and used to execute a good multicore OS. Something that's not achievable with any current GPU (both ATI's and nVidia's completely lack some control structures - both are unable to use subroutines and everything must be in-lined at compile time)
- unlike most current Intel x86 CPUs, features a shallow pipeline, executing instruction in-order. Hence, the Larrabee (and the Silverthorne which also have such characteristics) are regularly compared with old Pentiums (which also share those characteristics) since the initial announcement and including in TFA.
- feature more cores with narrower SIMD : 32 cores able each to handle 16 32bit float simultaneously. Whereas, for exemple nVidia's CUDA-compatible GPU have up to 16 cores only, but each able to execute 32 threads over 4 cycles and keep up to 768 threads in flight.
This enable Larrabee to cope with slightly more divergent code than traditional GPUs and make it a good candidate to run stuf like GPU accelerated RayTracing.
Hence all the recent technical demos running Quake 4 in raytracing mentionned on /.
That's for what Intel tells you.
Now the old and experienced geek will also notice that Intel has only kept making press releases and technical demo running on plain regular multi-chip multi-core Intel Cores (just promising that the real chip will be even better than the demoed stuff).
Meanwhile, ATI and nVidia are churning new "half"-generations each 6 months.
And the whole Larrabee is starting to sound like a big vaporware.
Parent
Re:What the hell is Larrabee? (Score:5, Insightful)
Not only is the power retarded, but ATI already can do 100% native ray tracing [techpowerup.com] which crushed intel bigtime.
I welcome intel trying to push for marketshare but it's going to be many generations before intel can play catchup on graphics cards...specifically when we get around to 32+GB of ram and you can afford a couple gigs for graphics (at which point we'll need 4+ gigs for graphics probably), the performance of an integrated solution will still be lacking. Graphics bandwidth and needs increases far exponentially beyond that of processing needs for anything graphics intensive by definition (currently).
Parent
Re:What the hell is Larrabee? (Score:5, Informative)
Not quite...
Larrabee is a general purpose number cruncher with high degree of parallelism.
NVIDIA/ATI are moving towards making their graphics cards capable of running general purpose code. Intel is coming from the other side, moving a general purpose parallel-compute engine towards doing graphics.
Yes it's a subtle difference and yes they'll meet in the middle, it's just a question of angles.
Intel wants the parallel compute market more than it wants the graphics card market so that's who it's pitching this at.
Parent
SIMD = Single Instruction, Multiple Data (Score:5, Informative)
Get your acronyms right....
I'm no expert but (Score:5, Funny)
The card features one 150W power connector, as well as a 75W connector. Heise deduces that this results in a total power consumption of 300W,
Um, that just doesn't seem to quite add up to me.
Re:I'm no expert but (Score:5, Informative)
Power can come from multiple sources. In this case, you have a 150W power connector (probably a 6pin PCIe one), and another 75W one (yet another 6pin PCIe). The remaining 75W comes from the PCIe connector itself.
Nothing terribly unusual - a number of cards are coming out in configurations like this, and 300W for a video card is starting to become the norm, depressing as it is.
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Re:I'm no expert but (Score:5, Funny)
Or from the loss of mental acuity due to serious RF interference melting your brain.
"Look at da pretty colors..."
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Re:I'm no expert but (Score:5, Funny)
It does if you work it out on a Pentium I [wikipedia.org] :D
Parent
good. (Score:5, Insightful)
on the basis that..
the design is well known, understood and has had rigorous testing in the field
they will no doubt fix any understood errors firstlimits the RnD to the multicore section
as long as the chip performs well for the silicon overhead then they should feel free to cram as many in as they want.
seems perfectly sensible to me.
I doubt it (Score:5, Interesting)
I doubt it. Maybe they mentioned the Pentium as an example to explain an in-order superscalar architecture as opposed to more modern CPUS.
-There is a lot of overheard in the P54C to execute complex CISC operations that are completely useless for graphic acceleration.
-The P54C was manufactured in a 0.6micron BiCMOS process. Shrinking this to 0.045micron CMOS (more than 100x smaller!) would require a serious redesign up to the RTL level. Circuit design had evolve with process technology.
-a lot more...
Re:I doubt it (Score:5, Informative)
The original Pentium (which went to 166Mhz, at the end, not just 75Mhz), used U and V execution pipes. No translation to micro-ops, and no "out of order". Indeed, there shouldn't be a need for that in Larrabee, anyway, given the number of cores. It would almost be better to get rid of the V pipe, and add SIMD, instead.
Your comments on CISC are bit off-base; the idea is to execute shaders in x86 machine code. They can be simple (limited flow control), or complex (general CPU/GPU).
"out-of-order" (ei. Pentium Pro and better) is not so good with that many cores doing that kind of work. It would get the hardware into a lot of trouble. Better to keep it simple, and add more cores.
A better start point would probably have been ARM, but that would lose the compatibility edge. If Larrabee works, it will take the GP-GPU market by storm. It needs:
1 - to publish itself as an NUMA access CPU (add a bit to tell the OS what it is for)
2 - compiler optimizations for the particular CPU architecture, preferably broken into two pieces:
2a - "straight line" shader code
2b - branching code
3 - a guide to the new NUMA characteristics.
With that in place, a standard (BSD/LINUX) OS will be able to use it for regular jobs. Or, for those special "I need the SIMD unit" jobs. The biggest hassle is trying to split control of those new CPU units between OpenGL and the regular scheduler (this is a kernel hack that Intel will have to make). It would be easier to jam this into OpenSolaris, but that isn't anywhere near popular enough.
Don't you want your video card to assist compiling large source when not gaming/modeling? Why not?
And, a few "extra" points
- Intel already has an optimizing compiler for the P54C architecture, and we have gcc.
- The architecture, including U/V pipelines only used 3.1 million transistors.
- A GeForce 7800 GTX has 302 million transistors -- 100x the number of the original Pentium processor.
So, I would think that using 32 "Pentium Classic" cores reduced would be quite feasible -- you need some (lots) of logic to ensure that they can all access their respective memories. The general SIMD implementation will take quite a bit of real estate as well. There is probably a budget of 600M transistors (wild ass guess) to Larrabee, estimate derived from power consumption estimates.
The gate size shrink should result in higher speeds. There may be a danger in the complex instruction interpretation routines, but these can be corrected. The single cycle instructions are already a (more than less) synchronous design, and should scale trivially.
Anything I am missing?
I, for one, am looking forward to buying a desktop super-computer with Larrabee.
Parent
Bill Waterson process (Score:5, Funny)
One does not "shrink" a chip by taking photomasks and shrinkenating.
'course not. You use a transmogrifier. In the industry, it is known as the "Bill Watterson" process.
It can also be used to turn photomasks into elephants, which, while less profitable, is immensely entertaining if the operator didn't see you change the setting.
Parent
Re:Pentiums? (Score:5, Funny)
Intel... where quality is job 0.9995675!
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