Relatively moderate performance in combination with four 850 Watt power supplies does not sound like good news as far as performance per Watt is concerned, but for completeness we shall give the figures. The X4600, on eight processors and 32GB of memory, uses 825 Watt when idle and 1030 Watt when loaded. With four processors and 16GB we measured 585 and 703 Watt, respectively. These figures have been obtained without the power saving option 'PowerNow!' switched on, because for some reason which did not become clear, we could not get this to work with our BIOS and/or Linux version. If it had worked, the idle consumption would have been lower in any case, and possibly we might have nibbled something off the consumption under load. The 2.66GHz Clovertown equipped with 8GB of memory required 355 Watt under full load, while the Fujitsu machine with its 1.6GHz CPU's and 4GB managed to make do with 279 Watt. This means that Clovertown easily achieves double the performance per Watt in the best scaling database.
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| Sun X4600 (8x Opteron 2.6GHz) |    1030 | |
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| Sun X4600 (4x Opteron 2.6GHz) | 703 | |
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| Melrow (2x Clovertown 2.66GHz) |    355 | |
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| Fujitsu TX200 (2x Clovertown 1.6GHz) | 279 | |
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| Melrow (2x Clovertown 2.66GHz) | 1264 | |
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| Fujitsu TX200 (2x Clovertown 1.6GHz) | 1205 | |
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| Sun X4600 (4x Opteron 2.6GHz) | 615 | |
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| Sun X4600 (8x Opteron 2.6GHz) | 519 | |
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X4600 conclusion
It is hard to be very positive about the 8-way Opteron. In the applications in which it isn't slower than a 4-way, the gains are often not impressive enough to justify the extra power consumption and cost. This isn't Sun's fault: the X4600 is stylish, user-friendly and complete - which is what we are used to from the company. It is simply AMD's architecture that does not seem very suited to scaling up to more than four sockets. There are some tests that demonstrate the potential, but those involve extremely well-parallelizable applications. For the price of 38,300 euros we do not even have to glance at the competition to find an alternative for this kind of software: the same money buys us almost ten(!) dual 2,8GHz Opteron servers with 4GB of memory. That's twenty processors for the price of eight. Given that some application is easily distributed, why not use a cluster? Easier said than done, but it does yield more possibilities for extension and flexibility.
The main advantage of a big machine over a cluster is that a large supply of memory is available which is shared by all threads, so programmers do not have to worry about synchronisation. The X4600 supports a maximum of 64GB of memory (the M2 even allows for 128GB) and that can hold a pretty big data set, for instance, for a scientific simulation. One location where the X4600 has been found to be a fit choice is the Japanese Tsubame, which at the time of writing is the ninth fastest supercomputer in the world. In a nutshell, the 8-way Opteron is interesting for tough simulations written by even tougher programmers, but the great majority will be better off with two or four sockets, or another processor that feels at home in heavy systems. Fortunately Sun is aware of this and can supply the X4600 with four sockets as well. This configuration still isn't a winner in our database test, but it does have a lot of success stories out there.
Fujitsu TX200 conclusion
This machine does not have the prestige an appearance of the Sun X4600, but armed with eight cores it can stick up for itself pretty well. Naturally the choice is always up to the customer, but we found the 1,6GHz Clovertowns of our test machine to be surprisingly competitive: they offer at least sixty to eighty percent of the top model's performance at less than half the price and a 2 x 40 Watt lower TDP - which makes for an excellent price/performance ratio. The only drawback is that the casing is fairly big. This does leave room for a lot of (cheap) 3,5" hard disks instead of the 2,5" server models but it surely isn't much fun to try and cram it into an overpopulated rack. In short, the TX200 is an interesting option for somewhat smaller companies that are above all interested in value for money and do not suffer from lack of space.
Acknowledgements
Tweakers.net would like to thank Hans Nijbacker, Bart Muijzer, Jignesh Shah, James van Geene, and Gert Jan van Gent from Sun Netherlands for cooperating to this article. We also thank Jeroen de Bruijn from Fujitsu Siemens Computers for lending us the TX200, our own sysadmins ACM and moto-moi for developing and executing the benchmarks, and Mick de Neeve for the English translation.
Previous articles in this series
12-12-2006: Intel Xeon 'Clovertown' 2.66GHz 13-11-2006: Intel Xeon 'Woodcrest' 3.0GHz (Apollo 5) 4-9-2006: Intel Xeon 'Woodcrest' 2.66GHz 30-7-2006: AMD Opteron Socket F 2.4GHz 27-7-2006: Sun UltraSparc T1 vs. AMD Opteron 19-4-2006: Xeon vs. Opteron, single- and dual-core (in Dutch)
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