Well, at least it involves voltage. 🙂
The techdoc for the Athlon64/Opteron is now available on AMD’s website.
It raises a number of questions, but perhaps the most important of these involves the voltages of the CPU.
If you go to page 48 of the document, you’ll see the voltage chart for the processors. Like the later Athlons, voltage is determined by five inputs set on or off.
This allows for 32 values, and all those values are determined. The voltage range is 0.800V to 1.550V.
Why is this a matter of interest? Well, the voltage of the initial Opterons is 1.550V, the maximum voltage allowed on the table.
This would be just like AMD selling an Athlon with a default voltage of 1.85V.
This means that unless you do a voltage mod, or a mobo manufacturer does one for you, you can’t increase voltage on these current CPUs.
Never in the history of these voltage values has the maximum voltage value been the default voltage.
The Mystery Deepens
A little item over at the Inquirer talks about a 2GHz Opteron showing up one of these days.
This is an unusual little critter in that it is going to have a lower default voltage than it’s older brothers. 1.45 volts as opposed to 1.55 volts.
Again, this has never happened before within a single manufacturing process before.
The recent multiple VID PIVs by Intel don’t fall into this category. Default voltage in these chips was lowered for the lower speed mult VIDs, not the higher ones.
The Likeliest Explanation
The most likely explanation for all this is that Opterons weren’t originally meant to have a 1.55V default voltage, but the only way AMD could get them out the door was to overvolt them.
The good news is that the process has apparently been improved enough so that for near-future CPUs, lower voltages will be possible.
P.S. Lower, but nothing like 0.8V. The voltage range appears to cover both 130nm and later 90nm chips.