what are the benefits of a dual cpu rig

rcf1987

2[H]4U
Joined
Aug 9, 2004
Messages
3,759
example if I have 2 amd 64 3500 will it be equal to a amd 64 7000 please explain the benefits the main uses and give details
 

defakto

2[H]4U
Joined
Jun 10, 2004
Messages
2,323
Well amd64 3500's won't run as dual processors, if you didn't know.

Dual processor systems allow the computer to better distribute it's load, some applications you may see close to a 100 percent increase, but mainly any type of rendering and encoding type apps for that. For general day to day use though, the system will "feel" smoother and be more repsonsive under a heavy load. No game yet takes full advantage of dual cpu's yet, quake 3 attempted to, but it wasn't any improvement, and doom 3 might, but i don't know yet on that one.
 

relic

[H]ard|DCer of the Month - August 2007
Joined
Mar 30, 2001
Messages
9,271
Most of the time the comment "If you need to ask, you don't need it." is true.
SMP is needlessly expensive unless you have an application that takes advantage of it.

Most applications are not SMP aware and in most 'average user' situations an SMP machine is no faster than single CPU system.

Multitasking, multiple simultaneous users (ie. terminal services) and multithreaded applications are where SMP shines. In these situations SMP will significantly outperform a single CPU. (note that P4 hyperthreading is still a single CPU and does not perform on par with an SMP machine in these applications)
 

Steel Chicken

Supreme [H]ardness
Joined
Jan 29, 2001
Messages
4,798
for gaming fastest single processor = best
for heavily used multi app workstations, or niche applications that use SMP = dual
 

Scorpionjwp

2[H]4U
Joined
Jul 14, 2004
Messages
2,094
For example some of the features and plugins for Photoshop is optimized for dual processing, you can use separate processors for different applications. Using affixity on the processors, setting one for gaming, setting the other for graphic programs or etc.

If you setup a dual processing rig, you will spend alot of time and money, more than you would If you have a single processor setup.
 

Tim_axe

Gawd
Joined
Dec 12, 2003
Messages
939
Dual CPU is used strongly where people need huge amounts of horsepower for scientific calculations. A lot of the clusters the Gov. is buying consists of Dual 3GHz Xeons. If you need 256 processors, it is cheaper to have 128 dual CPU rigs sharing a power supply, storage, memory, and network interfaces, than 256 individual computers. It lets you cram more power into less space, as long as the application can take advantage of two CPUs, or in this case 256 of them.

But some things, like games aren't optimized for running on two seperate CPUs. A game doesn't quite benefit from doing two simaltamious operations per clock. They benefit more from getting one thing done faster, instead of two things done together, even if in the end the MHz adds up the same.

But from your example, since we don't happen to have a 7000+ CPU today, running two of the current fastest processors will be as close as you can get to that. Although not everything can take advantage of it.


You also get twice the L2 cache since each processor has its own. So less cache swapping in many cases, I think. Instead of swapping the L2 on one processor 30 times for 30 programs, each processor could handle 15 programs, and swap the cache to RAM 15 times instead? I don't know too much about this stuff though, just a guess.
 

shieldforyoureyes

Limp Gawd
Joined
Aug 21, 2004
Messages
133
It's probably not going to effect any desktop users, but on
big systems, that savings in cache flushes is sometimes really
significant. The ideal of multi-processor systems is what they
call "linear speedup". Which is: 2 CPUs performing at exactly
twice the speed of one, 8 CPUs performing at exactly eight
times the speed of one, etc. Generally you get close to, but
don't reach linear speedup because not everything splits up
nicely, or CPUs wind up fighting for a single resource, or
something. But in rare instances, *better* than linear speedup
has been seen, and it was because of the decrease in cache
swapping that you point out.
 

Lazn_Work

Supreme [H]ardness
Joined
May 30, 2001
Messages
5,618
Tim_axe said:
You also get twice the L2 cache since each processor has its own. So less cache swapping in many cases, I think. Instead of swapping the L2 on one processor 30 times for 30 programs, each processor could handle 15 programs, and swap the cache to RAM 15 times instead? I don't know too much about this stuff though, just a guess.

Actually that is not entirely true: http://www.winnetmag.com/Windows/Article/ArticleID/7273/7273.html
" Intel-based SMP servers share data among processors and I/O subsystems. The possibility exists that copies of data that share an identical memory address and occur in processor caches and memory are inconsistent. Such inconsistency causes system operation errors. A well-designed SMP system maintains a consistent view of memory, or data coherency. If one or more processors cache copies of data with the same memory address, the system needs to synchronize the cached copies and the corresponding data in memory. Intel processors use a snooping protocol for data coherency. That is, when a processor bus processes a memory transaction, the bus will ask its other processors and processors on the remote processor buses whether they cache the data with the same memory address. If one or more processors cache the data with the same memory address, the system will synchronize the cached copies with the data in the memory and use the most recent data. However, snooping consumes extra processor cycles and bus bandwidth and increases traffic between the processor buses."

It can get even worse in linux: http://yara.ecn.purdue.edu/~pplinux/ppsmp.html
"Some MPS Pentium systems, and all MPS Pentium Pro systems, have independent L2 caches. (Each Pentium Pro "chip" really contains two chips: a processor and its L2 cache.) Separate L2 caches are generally viewed as maximizing compute performance, but things are not quite so obvious under Linux. The primary complication is that the current SMP Linux scheduler does not attempt to keep each process on the same processor, a concept known as processor affinity. Thus, having separate L2 caches may introduce significant overhead when a process is given a timeslice on a processor other than the one that was executing it last. "

==>Lazn
 

mosin

[H]ardForum Junkie
Joined
Sep 30, 2001
Messages
6,558
One not mentioned....

Dual processor rigs are so awesome that you do not feel the need to upgrade every few months. I can see me running this MSI K7D Master for a couple of more years. It does everything I need, and it does it well. Good server boards tend to be that way. :)
 

shieldforyoureyes

Limp Gawd
Joined
Aug 21, 2004
Messages
133
Woah - Linux doesn't try to keep processes on the same cpu?
That's really pathetic. Shouldn't be hard to fix though...
That's the first I've ever heard of an SMP OS not doing that.
(This is the sort of thing that makes Linux one of my least
favourite versions of unix.)
I definately agree that SMP machines age better - mine is
from 1993. :) (And it was in production use up until last
year at a University.)
 
Joined
Jun 11, 2000
Messages
693
Duallies vs. Singles... That's the eternal question for those who're curious but not yet converted... ;)

To be completely honest, if it's speed that you're after, go with the fastest, baddest, most overclockable single CPU with the most flexible board and the fastest memory will get you most of the way there. Duallies don't tend to give you that kind of speed. However, if you're after power and 'smoothness of operation', look no further than a duallie, even a relatively slow one.

It's like having twin turbo - you're not going to get that much faster than an out and out super car, but boy, you're going to have fun getting to the top speed with a twin turbo. Likewise, with duallies - you're not not suddenly find you manage to work that much faster, but you'd find task switching faster and some applications run better. Generally a 'smoother' computing experience.

:D
 

mosin

[H]ardForum Junkie
Joined
Sep 30, 2001
Messages
6,558
spikegifted said:
Duallies vs. Singles... That's the eternal question for those who're curious but not yet converted... ;) ...etc, etc...other good stuff...edited for brevity.
After you are converted, there is no going back. Suddenly, you lose interest in the mainboard forum, the video card forum, etc. You become one of the chosen few. One of the few who is suddenly sensible. ;)

There is no going back. Did I say that already ? :D
 

dagamore

Gawd
Joined
Oct 25, 2002
Messages
649
while a faster cpu say a fx53 or p4 3.4ghz will out perform a dual system in alot of programs, because of the lower overhead of only 1 cpu asking for resources, some applications will bennfit from a second cpu, most Divix encoders, and alot of tools in photochop will use both cpus, and you will notice a massive speed increase. but on my dual opti, i can host a game of empire earth, and play it, and burn a dvd and encoded a divix tv capture all at the same time, with out any real FPS loss on my gaming, i know alot of people with single cpu systems, that just love using my slower dual systems, because they are so much smother when you have 5 or 6 things all running full bore at the same time.
 

mosin

[H]ardForum Junkie
Joined
Sep 30, 2001
Messages
6,558
Single CPU machines = Ferrari
Dual CPU machines = Kenworth

We're the good old boys of the geek world. :D
 

Tigerbiten

[H]ard|DCer of the Month - February 2007/January 2
Joined
Sep 24, 2002
Messages
5,028
I've been useing my single 2400+ while I cleaned my dual 2400+'s heatsinks etc.
Same speed CPU's, FSB, etc.
Harddrives as slightly slower, IDE as Opposed to SCSI.
It feels so much slower.
It felt like an extra second to open each page etc.
When your used to the CREAMY SMOOTHNESS of a dual rig then theres no going back.

Luck....... :D
u=Tigerbiten.gif
 

teststrips

Limp Gawd
Joined
Jun 2, 2003
Messages
506
I sort of "fell into" a dual processor setup. Was browsing around on ebay, and saw an auction for a dual cpu board with matching 1600+ cpus (this is when the 2400+ was the fastest cpu available) The auction was a little less than 2 new cpus would have cost me (best price on pricewatch at the time), and there were 8 hours left. I figured, "I'll never win, I'll bid for the heck of it" I didn't consult the wife or anything... next day I find that I actually won the auction... i was quite happy.. the wife wasn't.

I've had the system for almost 2 years now and I love it. It's stable, and it's the first/only machine that I own that I can burn 2 different cds at the same time, plus still listen to music, check email and browse the web while downloading stuff.

I run a program that shows a bunch of info on my desktop, and uptime is one of the things I let on there... it isn't odd for me to have this system up and running without a reboot for a month at a time... it simply does not crash. Dual boards are built well, and the manufacturers put out quality drivers for them (vs the crap drivers a lot of "cheap" motherboards have.
 
Top