Version française
Home     About     Download     Resources     Contact us    
Browse thread
thousands of CPU cores
[ Home ] [ Index: by date | by threads ]
[ Search: ]

[ Message by date: previous | next ] [ Message in thread: previous | next ] [ Thread: previous | next ]
Date: -- (:)
From: Brian Hurt <bhurt@s...>
Subject: Re: [Caml-list] thousands of CPU cores


On Fri, 11 Jul 2008, Gerd Stolpmann wrote:

> Well, it is an open question whether this alternative holds. I mean
> there is a market, and if the market says, "no we don't need that
> multicore monsters", the chip companies cannot simply ignore it.

You're still assuming the chip companies *have a choice*.  And that 
there for, if the markets are just demanding enough, they'll go "oh, well, 
we didn't realize how important this is to you- we'll just go back to 
single threaded chips now..."  My point is that *all* of the chip 
companies are not this stupid, and if there was a choice, most of them 
wouldn't have choosen this route.  If there was one holdout, one chip 
company not going multicore, I'd probably agree with you.  I don't see the 
holdout (not among the chip makers at all pushing the performance 
envelope- yeah, a number of players in the embedded market aren't going 
multicore).

> Well, there is a another option for the chip industry. Instead of
> keeping the die at some size and packing more and more cores on it, they
> can also sell smaller chips for less. Basically, this alternate path
> already exists (e.g. Intel's Atom). Of course, this makes this industry
> more boring, and they would turn into more normal industrial component
> suppliers.

This has two problems, and "boredom" isn't one of them:

1) It undercuts the main selling point to get people to upgrade- increased 
performance.  We're used to buying new CPUs every yeah so often because 
the ones on the market are significantly faster than the ones we have 
(although the definition of "significantly faster" has slowly gone down 
over the years).

One of the ways the next generation was made faster was by throwing more 
transistors at the problem (allowing you to do more work per clock cycle). 
The other way was clocking the CPUs faster, but that also seems to be 
hitting problems (I'm not sure if the Power 6 means we may be exiting the 
clock speed drought, or if it's just a "revenge of the RISC" (i.e. 
something specific to the Power architecture that allows it to be clocked 
~2x as fast as the x86).

In either case, you're going to see a drop in the unit sales of "high end" 
CPUs.  And the third world isn't going to help with this- when I first 
became a professional software engineer, I bragged about having access to 
400MHz CPUs with 64M of ram- basically, computers with the horse power of 
a OLPC.

2) It really cuts into margins.  Generally, the amount of money the chip 
maker gets from selling a single $200 CPU is greater than the amount they 
get from selling 2 $100 CPUs, let alone 8 $25 CPUs.

And those are just the problems from the CPU vendor's perspective.  Now, 
lets look at this from the Software Developer's perspective:

We've fallen solidly off the Clock Speed ramp- even if we ignore the P4's 
inflated clock rates, it's been over 8 years since we've hit 1GHz, we 
should be at 8GHz or more now.  Now the 2-3GHz we're at.  And if we can't 
throw more transistors at the problem, CPUs simply aren't getting 
significantly faster.  Oh, there may be percentage-point gains now and 
again, but basically, where we are is where we'll stay.

Moore's Law just ended, from the software developers perspective.

No longer will the increasing speed of CPUs offset the increasing bloat 
and slowness of our code.

This turns out to be just a radical change of a different sort.

Brian