Multi-core CPUs

Peter William Lount peter at
Fri Oct 26 18:32:16 UTC 2007

tim Rowledge wrote:
> On 25-Oct-07, at 9:25 PM, Marcel Weiher wrote:
>> - Montecito, the new dual-core Itanic has 1.72 billion transistors.
>> - The ARM6 macrocell has around 35000 transistors
>> - divide the two, and you will find that you could get more ARM6 
>> cores for the Montecito transistor budget than the ARM6 has transistors
> Nicely pointed out Marcel! I've been trying to make a similar point 
> for about, oh two decades now....
> In fact around ten years ago TI announced some new technology relating 
> to wafer scale fabrication (I think, don't hold me to this) and as an 
> illustration of its possibilities they said it meant they could put 
> (something like) 128 StrongARM cpus each with 4MB ram on a wafer.  Now 
> let's say we take an easy path and put a mere 1000 ARM cores on a 
> chip, so as to leave some room for caches and transputer-like links (I 
> think someone actually did those for ARM at some point in the past) 
> and interface stuff. ARM 1176 cores are rated for 800MHz with claims 
> of up to 1GHz so we have potential for a quadrillion instruction per 
> second. Even Microsoft would surely have trouble soaking up that much 
> cpu with pointless fiddle-faddle.
> If we got no better than 1% useful work because of poor code we'd 
> still be getting 10 gips.


That is essentially what Tilera is doing with their Tile-N processors 
(where N is 36, 64, 128, 1024, 4096, ...). They are shipping the Tile-64 
chip now or shortly.

They have a design "kill rule" which states that if they increase the 
surface area by N% the cpu performance must also increase by at least N%.

The Itanium however is an awesome processor in it's own right regardless 
of the number of transistors it's using. It has predicate registers plus 
128 64 bit integer registers and 128 floating point registers. Lots of 
registers so the arguments about not enough registers can be put to bed. 
In fact the register file is sort of like but not quite like the Sun 
Sparc processors. It has instruction level parallelism which is good for 
a great many problems. Overall a very interesting and powerful processor.

When it comes to transistor budgets your analysis is correct... and may 
will the day in the market place. We'll see if Tilera or Intel will 
bring these internally networked grid chips to the mainstream market.


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