Author: Robert Hyatt
Date: 06:21:31 05/23/00
Go up one level in this thread
On May 23, 2000 at 04:08:16, Tom Kerrigan wrote: >On May 23, 2000 at 03:08:52, Bruce Moreland wrote: > >>On May 23, 2000 at 02:39:30, Tom Kerrigan wrote: >> >>>For some reason, people seem to believe that unless you're using 100% of your >>>processor all the time, you could make do with a slower processor. >>> >>>Okay, maybe your processor spends the VAST majority of its time waiting on you. >>>But that's not what matters. What matters is how much time you spend waiting on >>>the processor. >>> >>>I have an 800MHz Pentium III at work. It is very noticably faster than my 400MHz >>>Celeron at home. Even if I'm just browsing the web, I definitely prefer using my >>>work computer because I have to wait on it half as long. >> >>I'm all for faster computers, I just don't see what the benefit is of having two >>processors in a computer that's used by the typical home or business user. I >>may have to add "yet" to the previous sentence, but maybe not. >> >>People need more processors if: >> >>1) They do two CPU-intensive things at once. The typical user doesn't do this >>very much. >> >> or >> >>2) The application they are using can divide work. The typical application does >>not divide work. There are lots of reasons for this. We have a chicken and egg >>problem due to most computers being single processor. Another reason is that >>many tasks are inherently sequential. Another reason is that many tasks take >>very little time to execute, so multiprocessor overhead doesn't make a lot of >>sense. Another reason is that many tasks that take a lot of time take a lot of >>time due to bottlenecks other than the processor. And finally, if you have a >>task that is significant enough that you could notice time saved due to an >>additional processor, and it is able to be broken down into parts that can be >>done concurrently, multiprocessor code is often difficult to design, build, >>debug, document, and maintain. Adding multiprocessor features to most programs >>is a poor design decision. >> >>I am not a Luddite. If you have your normal single-threaded compute-bound app, >>and you double processor speed, the improvement is immediate, and I approve of >>this kind of improvement, most definitely. But take one of the many commercial >>chess apps and put it on a quad processor machine and see what happens -- >>nothing. This is also true of essentially *any* current app you can buy that >>does anything. >> >>Chess is actually a great case for multiprocessor computers, so for us, they are >>cool. >> >>But it will be a while until the typical user sees much advantage to adding >>another processor, I think. >> >>I see that multiple processor machines are becoming more common, but I can't >>understand why, and I can't understand why this trend would continue. >> >>bruce > >Sorry, I didn't read your post carefully and didn't realize you were talking >specifically about multiple processors. > >"Multiprocessing" will hopefully become widespread soon thanks to >multi-threading processors. This is an idea that [mainly] Compaq/Alpha has been >promoting. The idea is that if you have a processor with 2 execution units, you >can do one of two things: > >1) Use both units to execute a single thread; unfortunately, one of the units >will probably be idle a lot of the time. This is what most chips do now. > >2) Use one unit per thread, in the case that two threads are running. That way, >neither unit spins. > >The chip real-estate overhead for multithreading is evidently pretty small. >Hopefully it will be incorperated in mainstream chips soon. > >-Tom That is the main case we were discussing. I pointed out that within the next 3-5 years, most microprocessors will probably follow this path, so that each single processor chip will have 2 (or even 4) cpus internally. Multi-threading CPUS are a bit different, but not much. Some designs don't really have multiple cpu cores, but they are able to contain multiple processor states, so that context-switching is essentially free.
This page took 0 seconds to execute
Last modified: Thu, 15 Apr 21 08:11:13 -0700
Current Computer Chess Club Forums at Talkchess. This site by Sean Mintz.