Given that some parts of Photoshop use multi-threading, and if your computer is set to enable Hyperthreading, then the answer would be a partial yes. Not all of Photoshop is multi-threaded.
A CPU core with Intel's proprietary Hyperthreading implementation appears as two "logical" processors to Windows, and two threads can be executing simultaneously with some performance gain over each being executed in separate time slices on one processor.
Adobe would have to answer about whether any of its multi-threading implementation is specifically optimized to enhance operation on a system with Hyperthreading.
Yes, Photoshop uses hyperthreading when it would be faster.
But in many cases we can only use physical cores and not logical (hyperthreaded) cores because hyperthreading would make the process slower.
And we've been doing that since HyperThreading appeared in the Pentium 4.
June 5, 2011
I have the CS5 Master Collection. Since the advantage of of the i7 processor over the i5 is its hyperthreading ability, specifically, when would PS extended or the other programs, including Lightroom 3) use hyperthreading? I'm deciding whether or not the price is worthwhile on both a 64 bit DT and LT.
There are hundreds of threaded functions in Photoshop - I'm not going to list them all.
Again, Photoshop will use threading and hyperthreading whenever it provides a performance increase.
And Lightroom is the same in that regard.
June 5, 2011
Thank you for the clarification. Now I know it is worthwhile to pay the extra money for the i7 processor! I'd misread your original answer to mean the hyperthreading ability was used in a limited manner. I see now it is an integral part of PS and LR. Suggestion: Perhaps Adobe would consider clarifying this matter in its literature. (Please note the frustration of the client in this thread.) Very likely customers would opt for the higher rated processor, with subsequent increased satisfaction. Again, thanks for responding to the thread discussion!
If possible, please address the issue of AMD processors and hyperthreading. Is it possible for hyperthreading to be utilized only by an Intel processor?
Based on my own practical experience and testing, Hyperthreading offers only a marginal increase in performance over single core operation with many image processing tasks. I've come to believe this is because processing is being done on large datasets (images are usually many tens of megabytes in size, if not hundreds), meaning that the data can't all be held in the processor cache and main RAM access by the CPU becomes the bottleneck.
Hyperthreading's benefits vary with the operation. But in some cases it offers twice the performance compared to running without it.
Even with DRAM being the bottleneck, hyperthreading allows a few more calculations to proceed than without. And on the i7, you need hyperthreading to make the best use of the available system bandwidth.
Yes, I'd get the i7 chips and keep hyperthreading on.