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12-31-2009, 10:14 AM   #1
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cpu speed vs. # of cores

Greetings -

I truly don't understand cores vs. speed (and, for that matter, the influence that cache can/does have).

Let's take two processors, a 65w X2 3.0GHz Regor 250 and a 45w X4 2.3GHz Propus 605e. And let's ignore the $100 price difference.

Is one likely to be faster than the other for photo processing?

Or is it entirely (or almost entirely) program dependent?

Insight most welcome.

Thanks.

- Richard

12-31-2009, 10:34 AM   #2
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entirely program dependent, but nowdays I believe most photo editing programs (or more importantly, their processing functions) are multi-threaded, meaning work can be split up onto different cores, in which it will almost certainly be faster on a multicore.

If it is single threaded or a large portion of the heavy work is single threaded, then a faster single core would be faster for that particular function.
12-31-2009, 10:38 AM   #3
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That is a good question. With dual cores i had a fairly simple assumption. One core goes for everything OS related (disk reads/writes, memory operations, file browsing, ms Trojans etc.) an the other one goes for application specific code.

With more cores i'd think that each core goes for each app.+OS, but it certainly isnt so. For example, what happens when single app.+OS runs on a Quad core.

Basically, id expect that it should not be much application dependant. Applications use functions, functions are compiled into machine code. This code is stored in cache and small pieces of it should be fairly simple and straightforward (like set pixel 1 to x, set pixel 2 to y). At this point, it believe the CPU is able to decide, which operations it can execute in parallel and and pick them from cache. I hope im not confusing this with hyper threading.
12-31-2009, 10:46 AM   #4
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Maybe one day, but right now a set of instructions in serial fashion gets sent to one core, the cores themselves do not divy up the work. The OS and high level programming choose what can be done in parallel, and the OS sends that code, when converted to machine code to another core.

The way OS's work is they give each program a certain amount of CPU time. This amount depends on its priority, but every process gets a go. One CPU is never locked on one task (or bad code would effectively disable a core and lock up a computer). So one core does not go to each app - but the OS is smart and when going around its round robin queuing, it tries to assign the thread that has already been worked on on the previous worker, as to prevent cache misses.

12-31-2009, 10:49 AM   #5
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just to through a spanner in to the works, photo editing is very RAM hungry. The BUS speed and the amount of RAM will have a much greater effect than the difference between the two examples that you've put up.

If you want super, blow your socks of fast you'll need to be 64-bit multi core with a fast BUS and 16 Gig of RAM.

Sorry, this has probably confused you even more.
12-31-2009, 11:30 AM   #6
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RAM

Save the $100 and get more RAM, at the moment more ram will be the difference in photo editing. More is better, much more.

It's crazy to watch a Mac PRO with 32GB of ram in it. And it is the same on the M$ side, unless you are a hardcore gamer more RAM will give you more bang for your buck than a faster processor (except certain cross architectures i.e. i5 vs i7)

Though PLEASE don't get me started...I have things to do today.
12-31-2009, 11:54 AM   #7
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Ram is important but the Video card is another component that has to be taken into consideration. All the ram in the world isn't going to help your picture's if you don't have a decent video card to display it with. All in all there are alot of things that can impact the speed of the rendering of photos or video for that matter.

01-01-2010, 08:06 AM   #8
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QuoteOriginally posted by Dom Quote
just to through a spanner in to the works, photo editing is very RAM hungry. The BUS speed and the amount of RAM will have a much greater effect than the difference between the two examples that you've put up.

If you want super, blow your socks of fast you'll need to be 64-bit multi core with a fast BUS and 16 Gig of RAM.

Sorry, this has probably confused you even more.
Anyone know what constitutes a fast BUS speed these days?
01-01-2010, 08:14 AM   #9
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QuoteOriginally posted by expatCanuck Quote
Anyone know what constitutes a fast BUS speed these days?
Anything over 1000 MHz.
01-01-2010, 08:44 AM   #10
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The nice thing about multi core processors is that background processes (and they are legion in a PC, don't know about Mac) get spread around a bit so there is more cycle time to run applications.
However, more ram, faster bus speeds and separate swap drives will go quite far to speed up a decent dual core or fast single core processor.
If you are running limited ram due to a 32 bit OS (I'm still on XP Pro 32 bit), then you can get a big speed hike by installing multiple hard drives (the faster SATA ones are nice) and then handing them over to the OS and applications for swap.
I have Photoshop looking to a 2 drive RAID 0, and it is quite fast.
01-01-2010, 11:03 AM   #11
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RAMs first processor later.
01-01-2010, 12:39 PM   #12
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Sorry but I'm going to play the Linux card.

One of the easiest way to speed up any computer is to get rid of Microsoft. My main computer (2.3 GHz, quad core) is duel boot. Linux absolutely pisses all over Windows XP.

I only keep XP for the very few thinks I can't do on Linux yet.
01-01-2010, 12:47 PM   #13
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QuoteOriginally posted by Dom Quote
Sorry but I'm going to play the Linux card.

One of the easiest way to speed up any computer is to get rid of Microsoft. My main computer (2.3 GHz, quad core) is duel boot. Linux absolutely pisses all over Windows XP.

I only keep XP for the very few thinks I can't do on Linux yet.
Does Photoshop run under Linux?
01-01-2010, 12:47 PM   #14
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It makes a much bigger difference on Snow Leopard than on most other operating systems because Snow Leopard has Grand Central and many other things.

Like others have said, on a PC it's often program dependent.

Right now it doesn't make a major difference but it will eventually. One of the main reasons this was created was because a dual core 2.0Ghz was able to run much cooler than a 4.0Ghz could have. It made more sense to add cores rather than clock speed on each core. And I'm sure that trend will continue for quite a while.
01-01-2010, 01:00 PM   #15
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QuoteOriginally posted by Clicker Quote
RAMs first processor later.
not true if you're doing alot of rendering, e.g. filters in photoshop is mostly CPU [or even GPU] dependent.
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