On Saturday 30 August 2003 12:32, Bruce Marshall wrote:
I'll take a single cpu any day over multiple cpu's that DON'T ADD UP TO MORE MIPS than the single cpu. And that was my point.
A very well reasond answer Bruce. Unfortunatly it just proves you have never touched a Dual CPU machine running and SMP kernel in your life. Because in spite of your reasoning, the facts are the opposite. ANYONE who has used dualies would tell you two 500hmz CPUs easliy outperform a single 1Ghz cpu on the normal mix of applications you run on a typical linux machine, and they do it for LESS money. Usually enough less to afford the dual motherboard. CPU time is hardly ever the bottelneck in computers these days, except on the most compute intensive task. You assume in your SETI example that the CPU doing updatedb does nothing else except the updatedb. That's not true, it can run SETI while it is waiting on diskIO. Instruction fetch takes longer than instruction execution by several orders of magnitude. With two CPUs fetching data and instructions tasks are seldom ever backed up, and the machine remains responsive even under high load. A load of 50 would burry most single processor machines yet I've seen that often on a busy dual processor machine and it just runs right thru it. In all but the most compute intensive tasks I'll take two half speed CPUs over a single full-speed one any day. I ran RC5 crunchers in several of my machines for several years. The dualies (running two curnchers) always outperformed Single CPU machines twice their speed even though they theoretically should not have had an advantage on such a compute intensive task. If you're baseing your theory on Win2k or NT platforms you'd be right, Windows can only get 1.4 times a single processor performance with dual processors. Linux gets 2x. And when you want to do an addtionial task theres always a cpu cycle available - never any sluggish preformance. Don't theorize. Go get a dualie and bench it. -- _____________________________________ John Andersen