From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Original-To: caml-list@yquem.inria.fr Delivered-To: caml-list@yquem.inria.fr Received: from mail2-relais-roc.national.inria.fr (mail2-relais-roc.national.inria.fr [192.134.164.83]) by yquem.inria.fr (Postfix) with ESMTP id 62660BBB7 for ; Sat, 12 Jul 2008 19:24:18 +0200 (CEST) X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: Al0AAO5/eEjYi40Io2dsb2JhbACSLAEBAQEBCAUIBxGWIg X-IronPort-AV: E=Sophos;i="4.30,350,1212357600"; d="scan'208";a="13061438" Received: from mail-out8.nyct.net (HELO mail.nyct.net) ([216.139.141.8]) by mail2-smtp-roc.national.inria.fr with ESMTP; 12 Jul 2008 18:58:07 +0200 Received: from [192.168.42.2] (pool-96-250-133-152.nycmny.east.verizon.net [96.250.133.152]) (authenticated bits=0) by mail.nyct.net (8.14.2/8.14.1) with ESMTP id m6CGw3uf022919 (version=TLSv1/SSLv3 cipher=DHE-DSS-AES256-SHA bits=256 verify=NO); Sat, 12 Jul 2008 12:58:04 -0400 (EDT) (envelope-from bhurt@spnz.org) Date: Sat, 12 Jul 2008 13:35:48 -0400 (EDT) From: Brian Hurt X-X-Sender: bhurt@localhost To: Gerd Stolpmann Cc: caml-list@yquem.inria.fr Subject: Re: [Caml-list] thousands of CPU cores In-Reply-To: <1215781305.28798.19.camel@flake.lan.gerd-stolpmann.de> Message-ID: References: <1215717356.24773.17.camel@flake.lan.gerd-stolpmann.de> <1215781305.28798.19.camel@flake.lan.gerd-stolpmann.de> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed X-Spam: no; 0.00; gerd:01 stolpmann:01 choosen:01 intel's:01 clocked:01 boredom:98 drought:98 revenge:98 fallen:98 inflated:98 wrote:01 caml-list:01 sell:96 seems:03 unit:03 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