Photoshop 3.0.5 for Windows NT

Photoshop's SMP Capability Proves NT's Scalability

Image processing is one of the biggest resource-hogs of today's desktopapplications. It combines compute-intensive tasks with massive data-handlingrequirements. It has to digitally filter files from 10KB to more than 100MB insize. These requirements make image processing one of the top contenders amongapplications that could benefit from multiple-CPU support. Until recently, youcould run image-editing products on multiprocessor Windows NT systems, but theproducts weren't multithreaded and couldn't take advantage of the additionalprocessing resources available in NT. Now, Adobe Photoshop version 3.0.5 addsmultithreading to an already extensive list of capabilities.

Photoshop has been a standard in the desktop publishing industry forseveral years. However, it has been used mostly on the Mac--historically theleader in the desktop graphics market. When the PowerPC-based Macs arrived,their superior performance further enhanced Apple's leadership in this niche.The 486 and Pentium systems just couldn't keep up without special accelerators.

The market is changing rapidly: Adobe has shifted its focus from Macdevelopment to NT development to take full advantage of NT's inherentscalability--in terms of both memory and the CPU. With its most recent release,Adobe optimized Photoshop 3.0.5 for 32-bit operations and multiprocessorsupport. Multiple CPU support is accomplished via "real" multithreadedcompute operations, not just task-handling through the operating system. Thisversion of Photoshop is currently available for Intel systems, and a version forthe Alpha platform will be out soon. (There hasn't been any word on thedevelopment of a PowerPC or MIPS version.) Just imagine running Photoshop on aquad-processor 200-MHz Pentium Pro system with 128MB of RAM!

Because just about anyone who is interested in a new release of Photoshop isprobably intimately familiar with its previous feature set, I won't go into gorydetail about brush sizes and embossing tools. The program is basically unchangedfrom 3.0.4 in its tools and user interface, but it's now fully compatible withthe Windows 95 GUI. Some of its new features are:

New features also include a variety of changes specific to Windows 95, suchas common dialog support, the use of system colors and metrics, and right-handmouse-button support. This could prove to be important, especially if you usePhotoshop under the Explorer GUI. Photoshop also includes Win32s 1.30. (Win32sis a subsystem that allows the 16-bit environment of Windows 3.1 to run 32-bitapplications.)

Performance
At press time, Photoshop 3.0.5 was still in beta-testing, but I didn't runinto any problems either installing or running the application under Windows NTWorkstation 3.51.

I tested Photoshop's symmetrical multiprocessing (SMP) capabilities onseveral different systems:

I used the Performance Monitor (Perfmon) to watch the CPU loads duringvarious Photoshop operations and observed fairly equal usage of all theprocessors for all functions, including file open/close, filter operations, andimage editing (e.g., flip, rotate, and scale.) This showed that Photoshop wasindeed making judicious use of NT's multithreading capabilities. (Otherapplications that are not specifically designed for SMP will use all availableCPUs, but they pingpong the processes between the CPUs, rather than working onthem simultaneously.) I did, however, find that the results differed drasticallyamong the different test platforms. This indicates that hardware architecturehas as much effect on performance as CPU speed and available memory do.

For example, I ran the DFI system under a uniprocessor configuration bydisabling one CPU, and then I ran it in a dual-processor configuration. Thedifference in performance between the two was not significant--only about 10%(see graph 1 above). The test loaded and resized a stock 28.6MB JPEG file to a14MB file, a CPU-intensive, not disk-intensive, task. In fact, adding another32MB of RAM to the DFI system gave me a greater performance increase than addinga second CPU did--even two CPUs with 64MB of RAM didn't help much. I checkedwith Adobe, and company representatives admitted that adding a CPU gives onlyabout a 10% to 15% overall performance boost.

At first glance, this result seemed to indicate that your money would bebetter spent if you upgraded your memory to 64MB instead of buying anotherprocessor chip. But then I tried Photoshop on the Vectra and Netserver systems.The dual-processor Vectra XU 6/150 system ran at more than four timesthe speed of the DFI system with two CPUs, and the Netserver system with fourCPUs ran at nearly seven times the DFI's speed. Each additional CPU oneach HP resulted in approximately a 50% boost in speed. And the performancegains are even greater when compared to a standard 100-MHz Pentium machine. So,while more memory is an advantage to a certain point--I got more than aneight-fold improvement on the Vectra by bumping it from 32MB to 64MB ofRAM--having a machine designed to handle the task is even better. (I think thesmall shared CPU cache was the DFI system's downfall.)

Looking for Speed
Clearly, you need to look closely at any multiprocessor machine'sarchitecture before you invest in it. At present, the overhead for dualprocessors on some systems is just too high for individual applications toovercome. If you're looking for speed--and who isn't?--consider a Pentium Prosystem, where one faster CPU will give you a greater return than two slowerones.

Also, you needn't plan on putting more than 64MB of RAM into your system;that's the economical limit for improving system speed for Photoshop.

See the sidebar "KPT Convolver".