Demonstration of Hyperthreading at ComdexJust came back from Comdex last night. Intel had some demonstrations of Hyperthreading at the show, and it seems that they won a Best of Show at Comdex award from PC Magazine for it. For one of their demos, they had two identical 3.06Ghz P4s next to each other, one with HT enabled and one w/o. Both were running some 3D animation program but I don't remember which one. Anyway, he started rendering a frame of a complex 3D animation on both computers, and about a quarter of the way through the render, we saw the HT enabled computer begin another render line halfway down the frame, and when the original render line finished it's section, it started another line down in the unrendered part of the frame. The result was that the HT enabled computer finished the render about 3 seconds faster than the non-HT enabled one, out of a total render time of 30 seconds--not a significant margin it may seem, but if you multiply that by 30 frames per second by however many seconds your finished animation will be, the advantage of HT does add up.
In another demo, the Intel guy started rendering a video project on Premiere at the same time on both computers. He also had system performance monitor going on both comps to show CPU utilization. Once the rendering started, the non-HT enabled comp went to 100% CPU usage, while the HT enabled comp showed two bars for CPU usage--b/c the OS is tricked into thinking that this is a dual CPU system--and both bars showed 50% utilization. Now the frames per sec rendering rate for both comps was about the same, so HT had no advantage there, but then the demo guy started running a Photoshop script on both computers, and we watched in amazement as the HT enabled comp ran through the entire script in realtime, while the non-HT comp barely finished loading the script in the same amount of time. The final result was that the HT-enabled computer finished both the PS script and the Premiere render in less time than the non-HT comp. I don't remember precise times, but it felt pretty significant.
What was happening was that, for the non-HT comp, since Premiere was already utilizing 100% of the CPU, in order to run the Photoshop script the operation system had to interrupt the Premiere render in order to load and run the script, whereas the HT-enabled computer was able to go through the entire script w/o slowdown and w/o interrupting the render.
The Intel exhibitor explained that while doing something like a Premiere render, the CPU is using only a certain part of the processor, say the FPU unit, leaving other transistors of the CPU free. Thus, only a few parts of the CPU are actually being utilized 100%, while other parts remain inactive. What HT does is it sends another processing thread to those other parts of the processor that are currently inactive and puts them to use. Thus, HT allows the O/S to more fully utilize the ~entire~ processor, instead of just parts of it. So, even though a HT enabled computer won't render a Premiere video project significantly faster than a non-HT comp, HT does allow the user to do some other things on the computer w/o slowing down the render. It allows for significantly improved multitasking, so in the end you accomplish more in the same amount of time.
I've been a hardcore AMD guy since the beginning, but HT really does give Intel an advantage IMO, especially since AMD has lost most if not all of its price advantage recently.