John Fruehe - Director of Business Development for Server/Workstation AMD:
You are mistaken about TDP, because both companies deal with it differently.
Intel has 2 power levels: TDP and max power, (and now a third, "sustained power").
Take a look at the X5570 to see: [link]
Maximum power dissipation (W) 197.97; 155.56 (sustained)
Thermal Design Power (W) 95
So the way Intel always measured it in the past, Max power is the maximum power that a CPU can draw. Every transistor firing in a worst case scenario.
TDP is a de-rated value (used to be 80%, but it has been creeping down which is bad). Intel would take the maximum power, assume that the processor would throttle the clock down and then take that measurement (of a throttled processor) as the "TDP".
Since that time they have added a maximum sustained, maybe you can ask them what that means. I am assuming that max power is a spike power and that sustained is something that lasts more than a few milliseconds.
Regardless, the maximum power that the processor could conceivably draw is 197W.
Our TDP is equivalent to their max power, it is the maximum power the processor could draw, every transistor firing in a worst case scenario.
Our ACP is average CPU power. We run standard workloads, run them at 100% utilization and measure power.
Intel is not real open about max power. They used to post it online, but when they started getting pressure from AMD about those max power ratings, they stopped showing up online.
I'd love to have someone from Intel come here to debate this topic, because at this point, the specs (which they try to keep private) are not in their favor.
In designing a system to max power (which you have to do), we are not 42w disavantaged, we are actually 60w advantaged.
We do release max power. It is called TDP.
The reason the thermal design sheet lists TDP is because that is what you use to design systems. TDP is designed for system builders and OEMs. ACP is designed for customers in figuring out what they need for the data center.
ACP came into being a few years back because our TDP was 95W and it was rare that we ever had a part that even got above 50W. Customers were complaining that they were budgeting their racks for a certian amount of power, assuming 95W, and then ending up heavily under utilized. We were getting a lot of complaints from customers that we were too conservative and that this was leading to too much inefficiency in their data centers. I was on the receiving end of a lot of these conversations and they were not pleasant as data center floor space was the most expensive real estate in the building.
If you want a simple rule of thumb, use the following.
Most power a system can draw:
Intel = Max power
AMD = TDP
Typical power draw for standard applications:
Intel = TDP
AMD = ACP
If you are asking "why doesn't AMD just use TDP like the rest of the world" then you are on to something. We actually do. If you bother to go back to the wikipedia link above, you'll see TDP defined as:
"The thermal design power (TDP), sometimes called thermal design point, represents the maximum amount of power the cooling system in a computer is required to dissipate"
That sounds a lot like how AMD defines TDP, but that also sounds like how Intel defines max power. So, in reality, the "hoky" measurement is actually Intel's TDP because it does not represent what the rest of the industry means when they say TDP.
