AMD Athlon 4 - The Palomino is Here

Lower voltage, PowerNow! and finally, a Thermal Diode

Since the Athlon 4 is initially being launched as a mobile solution it does boast a few mobile optimized features. For starters, at 1GHz the Athlon 4 runs at 1.4V as opposed to 1.75v for the 1GHz Athlon (Thunderbird). This lower voltage operation is made possible by the transistor and layout optimizations we talked about earlier in this article.

The Athlon 4 does feature AMD's PowerNow! technology. For a quick refresher, AMD's PowerNow! allows the processor to dynamically change its clock speed and operating voltage depending on the application demands on the CPU. For example, a 1GHz mobile Athlon 4 doesn't need to run at 1GHz/1.4V if you are simply running MS Word. In this case it may throttle down to 500MHz/1.2V and automatically move up to 750MHz if you start to play a DVD (For more information on PowerNow! read our overview of the technology here).

The Athlon 4's PowerNow! implementation is relatively unchanged from the K6-II+ and K6-III+ processors. The only difference being that with both of those processors, in order to get respectable performance the processors would have to spend more time in the higher performance modes while the Athlon 4 can perform relatively well in its lower power modes. The Athlon 4's PowerNow! implementation allows for a total of 32 speed/voltage steps between 500MHz @ 1.2V and the maximum clock speed of the processor. Realistically speaking however you will probably only see between 4 and 8 steps used in actual implementations of the technology.

PowerNow! isn't too useful in desktop machines but mobile implementations of the processor will definitely benefit. In order for the technology to be taken advantage of there must be BIOS and chipset support.

The last feature of the Athlon 4 is an on-die thermal diode which measures the internal core temperature, much like what the Pentium III and Pentium 4 have. This is a very important feature because now the processor can not only tell what its internal core temperature is but, if implemented properly, the processor could throttle down or even shutoff if its temperature got too high.

There has been criticism for the Pentium 4 supporting this feature yet it is extremely useful. It would avoid the burnouts that have occurred in the past where users have either installed poor heatsinks, have failing fans or didn't even connect their fans. We have yet to confirm if the Athlon 4 has this sort of thermal protection enabled or not, but at this point there is nothing stopping AMD from doing so.

The on-die thermal diode requires the motherboard to be designed with it in mind. The thermal diode must be hooked up to a hardware monitoring chip, such as that integrated in VIA's 686 series South Bridges as well as BIOS support.