Dual core for CAD

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Over the past few months we’ve been hearing a lot about dual core CPUs, which contain two processor cores on a single piece of silicon. Both AMD and Intel have recently launched dual core chips, but what exactly do they mean for the CAD market?

Relative performance of workstations rendering under 3ds max 7.

There’s been a steady rise in CPU clock speed over the years, but the last 12 months has seen this trend stall, with increases in GHz virtually non-existent. One of the reasons for this is the amount of heat that modern processors generate. As the size of chips get smaller and clock speeds rise, thermal management is becoming more of an issue, and while elaborate heat sinks and fans have helped combat the problem, chip manufacturers have had to look elsewhere to improve performance. Enhancements to the FSB (Front Side Bus), to increase the speed the CPU talks to the memory, and additional Level 2 cache on the CPU, to help speed access to important and frequently used data, have helped boost performance, but where are the chip manufacturers taking us next?

The answer is ‘Dual Core’, where two processor cores are placed on a single piece of silicon. This new technology has strong analogies to current dual processor workstations, except with Dual Core there are two CPUs within one, rather than two physical processors placed on a motherboard. With two CPUs built into one chip, workstation users are able to multitask, or carry out two tasks concurrently. For example, you can model your latest design iteration using one processor, while the other runs a rendering on an earlier design.

In addition Dual Core processors can efficiently run multithreaded applications. These are applications that can be broken down into parts – called threads – that let multiple CPUs work on them for improved performance. At present most CAD software is not multithreaded. However, there are a number of multithreaded applications in areas that require lots of computational power. These include Finite Element Analysis (FEA) or Visualisation (rendering), where additional processors can help shave minutes or even hours off lengthy calculations.

Dual Core at Intel and AMD

Both AMD and Intel have just launched dual core chips. AMD is offering dual core models of its Opteron processor, while Intel has the Pentium D and Pentium Extreme Edition, which are dual core versions of the Pentium 4 processor. However, due to the additional heat produced by having two processors on a single chip, all of these dual core processors currently run slower than top-end single core processors. For example, AMD and Intel’s fastest dual core CPUs run at 2.2GHz and 3.2GHz respectively, whereas their fastest single core chips clock in at 2.6GHz and 3.8GHz.

In terms of technology and pricing AMD and Intel are currently approaching the dual core market from very different angles. AMD is positioning its dual core processors at the very high-end of the market. A dual core 2.2GHz Opteron is nearly three times more expensive than a single core 2.2GHz Opteron. As a result, you’re only likely to see dual core Opteron CPUs in dual processor workstations, to form a very high-end quad processor workstation.

Intel, on the other hand, is positioning its dual core Pentium D as a cost effective dual processor solution. One 3.2GHz Intel Pentium D 840 is cheaper than two 3.2GHz Intel Xeons. However, the Pentium D does not feature Intel’s Hyper-Threading technology, whereas the Xeon does. For those that aren’t aware, Hyper-Threading transforms each physical CPU into two logical processors, enabling it to handle data instructions in parallel rather than one at a time. However, it doesn’t do this as efficiently as two physical processors.

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While Hyper-Threading isn’t built-in to Intel’s Pentium D, the dual core Pentium Extreme Edition (EE) does feature the technology. As the Pentium EE already has two physical CPUs, this gives you four logical processors, the same you’d get with a dual Xeon. When Intel releases a dual core Xeon processor at the beginning of next year, you’ll be able to get a workstation with four physical and eight logical processors, which will completely change Intel’s dual core positioning.

Dual core on test

To see how good both AMD’s and Intel’s current dual core processors performed we tested them under the multithreaded visualisation application, 3ds max 7. Armari provided a dual AMD Opteron 275 Dual Core CPU (2×2.2GHz) workstation for the tests, while Evesham supplied a Pentium D 840 (3.2GHz) machine. Evesham also kindly lent us a dual 3.2GHz Xeon workstation so we could directly compare Intel’s dual processor solution, to its dual core counterpart. For good measure, we also threw in a 3.2GHz Pentium 4 640 workstation from CAD2, and a dual AMD Opteron 252 (2.6GHz) workstation from Delcam.

We rendered a single scene in 3ds max at resolutions from 250 x 250 pixels in increments up to 4,000 x 4,000. The results were extremely interesting.

Armari’s dual AMD Opteron 275 Dual Core workstation was by far the fastest machine on test. It was also interesting to see that Evesham’s dual 3.2GHz Xeon workstation was 20% faster than its dual core 3.2GHz Pentium D machine. This is down to the Xeon’s Hyper-Threading capabilities, which gives it four logical processors. Indeed, when we turned off Hyper-Threading in the bios the Xeon’s results were virtually identical to those of the Pentium D workstation.

As an aside, it was also interesting to note that Evesham’s dual 3.2GHz Xeon was nearly as fast as the dual AMD Opteron 252 (2.6GHz) workstation from Delcam. With the results so close we would also expect a dual 3.6GHz Xeon workstation to beat Delcam’s machine, one of the fastest on test this month. However, it should be noted that the Xeon puts in such good figures here because 3ds max is optimised for the Intel’s SSE2 instructions and is also able to take advantage of Hyper-Threading. As a result we wouldn’t expect these levels of performance to translate across all multithreaded applications.

Elsewhere we noticed that there was a lot less difference between the performance of all workstations when rendering at low resolutions, and the multi-processor machines only started showing their maximum performance when the renderings took several minutes (see graph above). This is because it takes a while for each individual thread to be assigned, so lower resolution renders have nearly finished before all the threads on each processor are running at full speed.

As expected we found no advantage in having two or four processors under single threaded applications. Here, Evesham’s Pentium D 840 (3.2GHz) machine, produced virtually identical results to CAD 2’s 3.2GHz Pentium 4 640. However, both dual core machines showed that they were able to multitask as well as their dual processor cousins when carrying out separate compute intensive tasks. However, when running four independent tests on Armari’s dual AMD Opteron Dual Core workstation, the performance slowed a little.

Rendering performance: 3ds max 7
Manufacturer CAD 2 Evesham Evesham Delcam Armari
Processor(s) 3.2GHz Pentium 4 640 2 x 3.2GHz Xeon 3.2GHz Dual Core Pentium D 840 2 x 2.6GHz Opteron 252 2 x 2.2GHz Dual Core Opteron 275
Graphics card PNY Quadro FX 540 ATI FireGL V5100 ATI FireGL V5100 Nvidia Quadro FX 1400 ATI FireGL V5000
Memory 2GB 2GB 2GB 4GB 4GB
Render Size Time taken to complete rendering (Seconds) (smaller is better)
250 x 250 48 38 41 29 27
500 x 500 120 77 87 66 52
1,000 x 1000 403 224 267 203 149
1,500 x 1,500 878 469 566 438 311
2,000 x 2,000 1,545 841 985 776 539
3,000 x 3,000 3,454 1,791 2,177 1,719 1,177
4,000 x 4,000 6,126 3,154 3,847 3,018 2,079

Conclusions

A few years ago there was very little choice as to which processor you chose to put at the heart of your Windows workstation. Over the past 12 months AMD has made a big impact with Opteron, Intel has introduced countless new Pentium 4 and Xeon models, and now both Intel and AMD have launched dual core CPUs. So where does this leave the average CAD user?

At this moment in time it’s fair to say all dual core processors are specialist processors. With current pricing AMD’s dual core Opteron is only for high-end users, those looking for ultimate desktop performance under multi-threaded, CPU-intensive applications. Indeed, with four processors to play with dual core Opteron could give engineers the power they need on the desktop, rather than having to farm studies out to dedicated compute servers.

Conversely, Intel’s current pricing of its Pentium D places it at the value end of the dual processor market, and while the Pentium Extreme Edition, with its support for Hyper-Threading, should bring dual core performance closer to that of Xeon-based workstations, top end Xeons will still have the edge due to their higher clock speeds.

Indeed, clock speed is a widespread problem for all dual core processors at the moment. In order to benefit from their multithreaded or multitasking capabilities, you have to take a performance knock under single threaded applications, of which there are still many in the CAD market. Until this changes – and we should start seeing the emergence of more multi-threaded CAD applications next year – dual core is likely to remain a valuable, but niche solution in the CAD sector.

www.intel.com
www.amd.com

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