AMD plays it cool with low-volt Istanbuls

AMD is today expected to complete its rollout of the six-core Istanbul series of Opteron processors with the final chip in the family: a low-voltage part for two-socket servers.

AMD has been dabbling with voltages and clock speeds to make Opterons of various performance levels and thermal envelopes since the 64-bit Opterons shook up the server racket in 2003.

The company was way ahead of the curve when it came to delivering low-voltage, low-frequency parts that had the same feature set as the standard x64 chips it sold, but for complicated reasons, server makers and customers were not quite ready to sacrifice raw performance for the kinds of performance per watt that the so-called Opteron Energy Efficient (EE) chips could deliver.

And so, AMD eventually kicked the EE parts over to an embedded business and didn't sell them through its normal channel to server OEMs. The low-powered parts were backburnered. But as the quad-core Shanghai Opterons lineup was expanded this past April on the sixth birthday of the Opteron chips, AMD recommitted itself to the EE parts as it saw its Highly Efficient (HE) parts start selling better.

That said, AMD is not crazy and is only trying to sell EE parts in high-end, four-socket and larger machines, but just in two-socket boxes.

The quad-core Shanghai chips had two EE parts, and both were rated at 40 watts like the new Istanbul Opteron 2419 EE part that comes out today.

Standard Opterons are rated at 75 watts, HE parts are rated at 75 watts, and Special Edition (SE) parts, which offer the peak performance in any Opteron generation, are rated at 105 watts.

Here's how AMD actually mixes and matches the voltages and clock speeds to get those numbers. The six-core Opteron 2419 EE runs at 1.8GHz and runs at 1.125 volts. That low-clock speed is what helps the part stay in that 40-watt thermal envelope. The two Shanghai parts, the Opteron 2373 EE and 2377 EE, ran at 2.1GHz and 2.3GHz, respectively, but because there was less stuff crammed into the chip, it could still meet the 40 watt envelope running at the same 1.125 volts.

Sports-edition speed

The Istanbul HE parts run at 1.15 volts and top out at 2.1GHz, yielding that 55 watts, while the standard parts raise the voltage to 1.3 volts and crank the clocks as high as 2.6GHz. Because heat increases on a log scale as volts and clock speed rises linearly, the relatively small jump in volts (13 per cent) and clocks (23.8 per cent) yields a much larger increase in heat dissipation (36.4 per cent).

The SE parts are really ridiculous in this regard, with clock speeds only rising by 7.7 per cent to 2.8GHz and voltage rising by 1.9 per cent, but heat dissipation increases to 105 watts, a jump of 40 per cent over the standard parts.

The Opteron 2419 EE chip is available today, and costs $989 each when customers buy them in 1,000-unit trays. On integer workloads (SPECint_rate2006), the six-core Opteron 2419 EE running at 1.8GHz is rated at 158, which is 32.8 per cent higher than the 119 rating that the four-core Opteron 2377 running at 2.3GHz. However, the Opteron 2377 EE only cost $698. You have to pay 41.7 per cent more dough to get that extra 32.8 per cent oomph.

These numbers won't get the hyperscale data center customers that AMD is targeting with the EE chips very excited. In fact, they will probably be annoyed that the cost for a unit of performance has gone up.