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The UltraSparc T1 'Niagara'
Back to Sun. During the dotcom hype, the company's processors were totally hip. There virtually wasn't a better way to impress investors than by showing off a 19" rack full of Enterprise or Fire servers to them. However, during the course of the last few years, Sun's competitors have walked off with the prizes more and more, which was reflected in consistently lower sales for the company. In 2001, the company sold 6.9 billion dollars worth of Sparc hardware; a 13.7% share of the total server market. In 2005, almost a third of that result had evaporated, in spite of the pain having been soothed the last few years by the sales of x86 servers, among which the Opteron line, which was introduced early 2004.
It goes without saying that Sun was not happy with this downward trend, but it did not seem to have much hope either to keep up with the rapid pace at which its rivals were improving their cores. When the company cancelled the UltraSparc V - the evolutionary successor of the current UltraSparc IV+ - it became clear that Sun had thrown in the towel as far as singlethread performance was concerned. This radical step indicated that Sun was betting on Niagara, the codename of a design it got its hands on through the acquisition of Afara Websystems in 2002, for its future as a chipmaker. Originally intended as a network processor, the Niagara architecture does not so much depend on a fast core as on a combination of CMT and CMP - Chip Multi-Threading en Chip Multi-Processing. This concept is known as 'Throughput Computing', or 'CoolThreads Technology' by its current hip official name.. Sun uses to following analogy to illustrate the concept for lay persons:
Of course other manufacturers have witnessed the same trends as Sun did, hence the advent of multicores had been widely predicted – and even partially undertaken – before Sun made its strategy public. The difference, however, is that the competition does not approach the issues as radically, and still tries to find a balance between advanced cores and a decent singlethreaded performance, with a moderate degree of duplication of these. For now, most companies agree that two cores per socket is fine, although the quadcores are appearing on the horizon. Sun is not wasting any time and has jumped straight to eight cores with the first product in the series.
Niagara cores are comparatively simple. Other than multithreading, at the conceptual level there isn't a great deal more going on than in a 486: there is a maximum of one instruction per clock tick; sets of instructions are handled on a first come first served basis. The multithreading isn't too advanced either: at every clock tick, execution shifts to the next of a maximum of four active threads. This is a great deal simpler than HyperThreading (SMT), where instructions from multiple threads may go into the pipeline together. However, by keeping the design simple, it is possible to integrate eight of them together with a quad channel memory controller and a shared FPU onto a chip, without power consumption going through the roof. The full specifications, compared with those of the Opteron, are as follows:
Doing some very superficial yet illustrative maths yields the following statistics: the Niagara processor needs 48mm², 38 million transistors and 10 Watts per core, while the Opteron requires 97mm², 117 million transistors and 48 Watts. This means that Sun has come with a unique design that hardly looks like anything made by the competition. Actually, it is valid to wonder if one can speak of competition in this respect: the T1 has a number of properties that put it outside a large share of the market. A lack of FPU power, the impossibility of installing more than one chip per motherboard and poor singlethread performance pretty much guarantee it is no threat to Intel, IBM or AMD. But there are a number of specific areas where Niagara excels, as Sun likes to emphasize on its website. The company also stresses the chip's favourable performance per Watt. Hence, it is about time to take a close look at this type of server, and see how it stands up against the ‘ 'traditional' Opteron configuration.
It goes without saying that Sun was not happy with this downward trend, but it did not seem to have much hope either to keep up with the rapid pace at which its rivals were improving their cores. When the company cancelled the UltraSparc V - the evolutionary successor of the current UltraSparc IV+ - it became clear that Sun had thrown in the towel as far as singlethread performance was concerned. This radical step indicated that Sun was betting on Niagara, the codename of a design it got its hands on through the acquisition of Afara Websystems in 2002, for its future as a chipmaker. Originally intended as a network processor, the Niagara architecture does not so much depend on a fast core as on a combination of CMT and CMP - Chip Multi-Threading en Chip Multi-Processing. This concept is known as 'Throughput Computing', or 'CoolThreads Technology' by its current hip official name.. Sun uses to following analogy to illustrate the concept for lay persons:
The answer obviously depends on the number of passengers.
Of course other manufacturers have witnessed the same trends as Sun did, hence the advent of multicores had been widely predicted – and even partially undertaken – before Sun made its strategy public. The difference, however, is that the competition does not approach the issues as radically, and still tries to find a balance between advanced cores and a decent singlethreaded performance, with a moderate degree of duplication of these. For now, most companies agree that two cores per socket is fine, although the quadcores are appearing on the horizon. Sun is not wasting any time and has jumped straight to eight cores with the first product in the series.
Niagara cores are comparatively simple. Other than multithreading, at the conceptual level there isn't a great deal more going on than in a 486: there is a maximum of one instruction per clock tick; sets of instructions are handled on a first come first served basis. The multithreading isn't too advanced either: at every clock tick, execution shifts to the next of a maximum of four active threads. This is a great deal simpler than HyperThreading (SMT), where instructions from multiple threads may go into the pipeline together. However, by keeping the design simple, it is possible to integrate eight of them together with a quad channel memory controller and a shared FPU onto a chip, without power consumption going through the roof. The full specifications, compared with those of the Opteron, are as follows:
| Sun UltraSparc T1 | AMD Opteron (Revision E) | |
|---|---|---|
| Cores | 8 | 2 |
| Threads per core | 4 | 1 |
| Prod. process | 90nm | 90nm |
| Clock speed | 1,0 - 1,2GHz | 2,2 - 2,6GHz |
| Nr. of transistors | 300 million | 233 million |
| Size | 380mm² | 194mm² |
| Pipeline design | In-order | Out-of-order |
| Pipeline length (integer) | 6 steps | 12 steps |
| Pipeline length (float) | N/A | 17 steps |
| Max. instructions per tick | 1 | 3 |
| L1 cache (per core) | 8KB data, 16KB instruction | 64KB data, 64KB instruction |
| L2 cache | 3MB (shared) | 2MB (1MB per core) |
| Memory controller | 4x DDR2-533 (34,1GB/s) | 2x DDR400 (12,8GB/s) |
| Internal communication | Internal crossbar (134GB/s) | HyperTransport (24GB/s) |
| Nr. of socket pins | 1933 | 940 |
| TDP | 79W | 95W |
Doing some very superficial yet illustrative maths yields the following statistics: the Niagara processor needs 48mm², 38 million transistors and 10 Watts per core, while the Opteron requires 97mm², 117 million transistors and 48 Watts. This means that Sun has come with a unique design that hardly looks like anything made by the competition. Actually, it is valid to wonder if one can speak of competition in this respect: the T1 has a number of properties that put it outside a large share of the market. A lack of FPU power, the impossibility of installing more than one chip per motherboard and poor singlethread performance pretty much guarantee it is no threat to Intel, IBM or AMD. But there are a number of specific areas where Niagara excels, as Sun likes to emphasize on its website. The company also stresses the chip's favourable performance per Watt. Hence, it is about time to take a close look at this type of server, and see how it stands up against the ‘ 'traditional' Opteron configuration.
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