Socket A Mobo Voltage

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I got this very good question this morning:

The only board that I know of that has a core voltage range of 1.1-1.85v is the Abit KT7A and most of the others including the KK266 is from 1.5-1.85v. Why is this important as most processors are 1.6v and above? Because future AMD processors will require voltages below 1.5 volts . . . . I know that the Palomino should be pin compatible with the socket A and the KT133/KT133A chipsets should work with it but the voltages are an issue.

Can the voltage ranges be increased with a BIOS upgrade or is a physical change needed on the board?

An answer (sort of):

AMD has had two standards for voltage regulation for Athlons. The first (for Slot As) supported voltage as low as 1.3V; the newer one supports voltages as low as 1.1V.

While the public Socket A documentation doesn’t definitively state that all mobos must be able to get down to a 1.1V range (it refers to a techdoc not publicly available); the earlier Slot A information did indicate mobos were required to cover the whole range. All the voltage regulators I was able to check on socket A boards (see below), support voltages down to 1.1V.

I find it pretty unlikely Palomino is going to be much under 1.5V; extremely unlikely it would be under 1.3V.

Voltage Is Not The Problem; Amperage Is

Wattage is Amperage Times Voltage: Amperage is How Much Power. Voltage is How Fast Does It Go. Voltage doesn’t kill you; amperage does.

Just supporting X voltage isn’t good enough. A few of you with Abit BX boards should remember that they, too, “supported” voltage down to low levels, but when Coppermines came out, they backed off from any claims of these processors actually working at those voltages. Most ended up working, but some didn’t.

We’ve seen estimates around as to how much amperage the Palominos are going to require, and they’re pretty high, up to 46A (as opposed to a bit less than 40A on the fastest TBirds today).

To handle Palominos, not only does the voltage regulator have to provide the right voltage; they also have to be able to handle the amperage.

To get an idea of what I’m talking about, take a look this list from one company that makes voltage regulators. Look towards the bottom of the page, at “Multiphase Output.”

You’ll see some can handle only 45A, and some can handle 100A. Obviously, you’d rather have the latter.

Note that one of the voltage regulators listed that’s rated up to 100A is the HIP6301. See here for its datasheet.

This chip is used by the Abit KT7 and KT7A. The same chip is also used by the IWill KK266.

So to answer the gentleman’s question, the IWill hardware is just as capable as the Abit board to handle any Palomino. A BIOS change will be needed, but that shouldn’t be any big deal. Update: 2/22/01: IWill will update the BIOS to do just get next revision.

The Epox 8KTA3 uses a different voltage regulator (the CS5303), but it, too, looks up to snuff. See here for details.

The Asus motherboards, on the other hand, use an older generation of voltage regulator; the CS5322. You can see the datasheet for it here. If you’d like to comparison
between the 5303 and 5322, look here. It can get down to 1.1V, too, but while I’m not an electrical engineer, it doesn’t seem to be as advanced as the other chips. Not even going to pretend I understand 95% of the datasheets, but if you look at Figure 1 in both datasheets, the one for the 5303 refers to 60A, while the one for the 5322 refers to 35A.

The 5322 may well be good enough to handle a Palomino, but if I had doubts about any of these voltage regulators handling a Palomino, it would be this one, and I’d get something definitive from Asus before buying one.

Email Ed


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