Two for the price of one

Two for the price of one

There are many ways to tally the cost of computer hardware. During the lifetime of a PC server or workstation, the machine consumes capital in acquisition, support, maintenance, upgrades and operation (power and cooling). The ideal system balances performance with low initial and continuing costs.

The best balance between power and value will be struck by systems built using the latest dual-processor PC platforms. New technology has brought new choices and competition to the dual-CPU system market, driving prices down while maintaining crucial operating system and application compatibility. After working with three new platforms offered by Intel and AMD, those of us in the Test Centre are left wondering why anyone would buy a PC server or workstation with only one processor.

But despite our enthusiasm for these new machines, we still see some drawbacks. The AMD Athlon MP, Intel Tualatin and Intel Xeon platforms are far from interchangeable; each uses unique components. Nor can any of these new CPUs be used to upgrade existing PC servers or workstations. Buying into one of these dual-CPU platforms means buying entirely new PCs and investing in upgrade and repair parts that are incompatible with currently deployed PCs.

Nevertheless, we think they're worth the investment, especially now that component prices are irresistibly low. Thanks to low demand and cutthroat competition between AMD and Intel, you can buy dual-processor systems for what you would have spent on single-CPU systems just a year ago.

Does every application benefit from multiple CPUs? Certainly not. Not every PC user needs a workstation and not every server is CPU bound (spending more time computing than moving data around). But every company has a core of demanding PC users who waste time waiting for their computers to finish a job, be it compiling source code, rendering a 3D image, editing a digital video, or performing any gating task that must be completed before the user can move on. For these users, and for servers generating dynamic or secure content, a second CPU is like a spare PC within a PC. Dual-processor machines can't quite do twice as much work in the same amount of time, but the performance gain is substantial enough to justify the additional expense.

We tested the latest dual-processor platforms using systems that, to varying degrees, we constructed ourselves. Building our own generic systems gave us two advantages: we didn't have to wait until Compaq or Dell started shipping Tualatin, Xeon or Athlon MP hardware before we could test the platforms; and our findings wouldn't be skewed by a single vendor's proprietary spin on the technology. Because our tests were performed on components, and not on commercially available products, they do not constitute formal reviews. We performed them in an attempt to tease out essential differences among the platforms.

For the testing, we tried to create as level a playing field as possible. We installed 1GB of RAM on each system, performed a clean install of Windows 2000 Professional with Service Pack 2, and used BAPCo Sysmark 2000, SPECint2000 and SPECfp2000 benchmark software to gauge performance. BAPCo (Business Applications Performance Corporation) Sysmark measures system performance by simulating the usage of real applications such as Adobe Photoshop and Microsoft Word, whereas SPECint2000 and SPECfp2000 measure compute-intensive integer and floating point performance, respectively.

Note that we adapted the SPEC (Standard Performance Evaluation Corporation) tests to make them more applicable to dual-processor systems. Specifically, we ran three parallel copies of each benchmark to ensure that both CPUs remained burdened until the end of each test. The charted results show the sum of the three test processes. Our approach isn't sanctioned by SPEC and our results shouldn't be compared with those of other SPEC runs.

The benchmarks revealed some performance differences among the platforms (see charts). Intel's Xeon led in floating point performance, but fell short in integer performance. For Intel's Tualatin, the reverse was true. AMD's Athlon MP took second in the SPEC integer and floating point tests, but proved slightly faster overall in the BAPCo application simulation tests.

The most significant difference among these platforms is cost. The cost of two CPUs and 1GB of matching memory is just $US562 for Athlon MP, compared to $718 for Tualatin and $1075 for Xeon. When it comes to balancing price and performance, Athlon MP is the clear winner.

Intel Xeon

Intel's new Xeon processor shares its name with technology that dates back to the Pentium II. All Xeons - new and old - are built especially for multiprocessor systems. The new Xeon uses Pentium 4 technology, but it is not compatible or interchangeable with the Pentium 4. Xeon also requires a special power supply, a fact we stumbled upon while building our system.

The Supermicro P4DC6 motherboard we used for testing comes with massive heat sinks to draw the heat away from the Xeon CPUs. Power management circuitry keeps Xeon cool under less trying workloads, but when subjected to the stress of our benchmarks, the dual 1.4GHz Xeons pumped out as much heat as a hairdryer.

Previous Xeon models benefited from large, fast cache memories, but the new Xeon does not; its 256KB cache is the same size as that in the desktop Pentium 4. Xeon's performance in our benchmarks, although respectable, would have been boosted by a larger cache. In all, Xeon's performance, weighed against Tualatin's lower power draw and Athlon MP's lower acquisition cost, made it our third choice in this roundup.

Xeon carries the highest acquisition and upgrade costs because of its use of expensive Rambus memory. For example, memory vendor charges approximately twice as much for Rambus as for its next most expensive RAM. Rambus is much, much faster than other types of memory, but the small gain in application performance doesn't justify paying Rambus's higher cost or risking abandonment when Intel moves to DDR (double data rate) memory, the type of RAM used in Athlon systems.

Xeon's lead in some of our benchmarks is probably due to its higher clock speed (1.4GHz compared to 1.2GHz for Athlon and Tualatin) rather than the superiority of Rambus. If Intel lowers the price of Xeon, it'll make a cost-effective workstation chip. But we're most interested in seeing what the next generation of large-cache Xeons, paired with affordable DDR memory, can do for servers, especially larger machines with four, eight or more CPUs.

Intel Tualatin

The surprise entry in this contest is an Intel Pentium III chip bred especially for low power consumption. This cool-running CPU, code-named Tualatin, grabbed our attention for being the only chip that wasn't topped by a gargantuan heat sink and fan. Tualatin's benchmark performance also surprised us. We like this processor for two roles: the desktop, where low power means low operating costs and quiet running; and the clustered server, where you might rack up as many dual-processor Tualatin servers as needed to do the job.

Our Tualatin review unit was a Supermicro 6011L, a sleek 1U-high (1-3/4 inch) rack-mountable number with dual removable Ultra160 SCSI drive trays. It cost only $US100 to equip the 6011L with a gigabyte of Registered PC133 RAM. If Intel dropped the price on Tualatin it could make a lot of trouble for AMD. As it is, we hope that Tualatin starts a trend toward fast, low-power CPUs.

AMD Athlon MP

AMD has been manufacturing Intel-compatible CPUs for many years, primarily targeting the low end of the market with affordable alternatives to Intel processors. Athlon MP is AMD's first dual-processor architecture, and its first showing is impressive. We tested two Athlon systems, one workstation and one server, both based on Tyan's Thunder K7 motherboard. The combination of low cost and excellent performance make Athlon MP our first choice, but AMD will have to fight to keep that slot. Intel has aggressive plans for faster CPUs, with the heady 2GHz barrier slated to fall within a few months.

At just $US324 per pair, the 1.2GHz Athlon MP CPU is the least expensive in our roundup. Registered DDR memory costs more than ordinary RAM - charges $US238 for a gigabyte of DDR compared to $100 for standard PC133 memory - but prices are falling as Athlon gains wider acceptance.

Misgivings about compatibility with applications built for Intel processors are unfounded. The Athlon MP mimics Intel CPUs perfectly, even emulating Intel's digital media acceleration technology. Intel will probably maintain its lead in clock speed. Despite this, AMD wins many speed contests (including two of our BAPCo tests) due to its innovative design. All three of these dual-processor platforms would be good investments, but the price/performance crown belongs to AMD.

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