Dual 2.7 GHz - what is it exactly?

HomunQlus

HomunQlus

Artifical Lifeform
Since a few days the new PowerMac is out, with Dual 2.7 GHz and stuff.

I checked the Amazon website, and it says in specs:

Dual 2.7 GHz PowerPC G5, 1.35 GHz per processor
Click to expand...

I always thought the a dual PowerMac would have, in this case two 2.7 GHz processors, that is why it's called "Dual". I always see two processors when I see a Dual PowerMac.

So, my question: Is it 2x 2.7 GHz or is it "only" 2x 1.35 GHz?

:confused:
 
thats quite confusing, but it's the front side bus speed in ghz, which on the powermac g5s is half the speed of the processors - on mine the FSB is 900mhz
 
ha ha no. nice thinking. some software reqirements have been in the past, for example, 1ghz g4, or dual 800mhz g4
 
well.. you could say like this:
supposed a G5 2.7ghz performs like a P4 3.6ghz and an application has a 100% benefit of two cpus, then you could say, that the Dual G5 2.7ghz performs for that app like a G5 5.4ghz (if that one had a linear performance graph) or like a P4 7.2ghz.
 
Dual processor systems don't double the speed of the computer. All they do is share tasks amongst one another at the same clockrate. So two 2.7 GHz processors won't function like one 5.4 GHz processor. What they will do is make it less painful to multitask, and will allow smoother multimedia and gaming experiences since both processors are sharing the workload. Of course, you would have to have an operating system and applications that take advantage of the processors in this fashion. Thankfully, Mac OS X does this natively.

There used to be an extension available for older version of the Mac OS before X during the days of the Daystar Digital Mac clones and the Power Mac 9600 MP, but it wasn't the best setup. Applications that weren't written to recognize the second processor just sat there unused, making the system perform slower than a single processor system. The best you could get was have on processor perform calculations, while the other maintained the OS or some other function. Tasks were strictly delegated and weren't shared like they are now.
 
thats a thing to remember, and should be highlighted.

all software has to be written to take advantage of the second (or third, or fourth etc) processor, or it will just sit there idle. MacOSX IS written to take advantage of this, as are adobe programs, macromedia, high-end scientific research software and most pro-apps.

the worst is windows native software - windows world has never really woken up to multi-processing (you can buy dual-xeon pentiums, but they are more designed for linux/unix systems) and so the apps designed for windows then ported to mac (cubase, ms office etc) are not really optimised for dual processing usually.

at the end of the day, the processors can't exceed the clock speed they are limited to - a 2.7 ghz processor will only ever go that fast. another one sitting next to just allows another program to go the same speed at the same time. so in theory, you get two things done twice as fast, but if only one thing is being done, it can only go as fast as the limit on the processor
 
Not everything can be coded to work with symmetric processing. In fact, you incurr some overhead when designing multithreaded apps, simply because the data has to be rearranged in a way to allow for both CPUs to read/write to the data source simultaneously. That is why we probably won't ever see an exact 200% increase in performance.

In most cases, such as office tasks that you mentioned, you're better off just doing it single threaded. So it's not as bad as you make it out to sound. But just for kicks, I opened up Access in Windows and looked at my task manager, which tells me that Access is managing 3 threads, even without a document opened.

These apps ARE multithreaded, but the job they're doing doesn't necessarily need or benefit from multiple threads so you don't see both CPUs loaded at 100% all the time. Most of the time, at minimum an app that does heavy processing (in a spreadsheet or database for example) ideally should put that heavy duty work on a seperate thread. That way the app doesn't just hang and stop responding to user input, such as canceling the current task. But I will admit, things don't always happen as expected :)

Lt Major Burns said:
so in theory, you get two things done twice as fast, but if only one thing is being done, it can only go as fast as the limit on the processor
Click to expand...
Small correction. You get 2 things done at their normal speed, not twice as fast. Each task gets a CPU to itself, rather than sharing 1.
 
yes, thats what i meant. i just couldn't get my brain to make words with both the two things working at once, you save time by half (in theory) as it is simultaneous. save time by half = twice as fast. in a sandbox world. but no, nothing goes faster than the limit of the clockspeed, which was my original point
 
*smacks forehead* I just got it. Yeah there wasn't anything wrong with your wording. Twice as fast as in the lump sum of the jobs you're doing, not the individual tasks.

Pfft, leave it to a programmer to screw up English. Sorry about that :eek:
 
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