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Topic Title: Mobile Athlon64's compatibile Desktop MB's?
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Created On: 05/18/2004 12:32 AM
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 05/18/2004 12:32 AM
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omegabit
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Joined: 05/16/2004

I am interested in building a server with low power/cooling reqs at idle (which is most of the time). According to AMD's thermal specs, the lowest "Cool & Quiet" P-State (e.g. for a ADA3200AEP5AR) Desktop 3200+ is 22W at 1.10v. By comparison, a Mobile Athlon64 AMN3200BIX5AR comes in at 13W at 0.95v. (This is in the same range as a much lower performance VIA C3!

Tom's Hardware claims that the only difference between desktop "Cool & Quiet" and the mobile 64's PowerNow is that the laptop starts at the lowest level and climbs as needed, and the desktop does just the opposite.

1. Would a MB which supported "Cool & Quiet" (e.g., MSI Neo K8 or ASUS K8V) for a desktop be able to control a mobile chip which implements "PowerNow"?

2. Assuming a lidless mobile athlon CPU pins are identical with a desktop 794 socket, would it be possible to set a lower voltage for each PState in the BIOS (is this even controlled by the BIOS?), or would you have to specify one voltage & multiplier setting at bootup?

3. Would it be possible to programmatically change the CPU's PState on the fly based upon its current load, or is this something that occurs below the operating system level?

4. Has anybody else tried this or heard of why it would or wouldn't work?

Thanks for any info you can provide.
 05/18/2004 01:32 AM
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Greyhound
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QUOTE 1. Would a MB which supported "Cool & Quiet" (e.g., MSI Neo K8 or ASUS K8V) for a desktop be able to control a mobile chip which implements "PowerNow"?
Hmmm...C'n'Q and PowerNOW! are very similar...however, while C'n'Q only switches between 2-4 set P-states, PowerNOW! uses a more dynamic adjustment...
Personally, i would be inclined to think that PowerNOW! will NOT work in a desktop motherboard and that using C'n'Q with a mobile part would most likely result in the CPU switching between its minimum and maximum P-States only - but that's just my guess...Mobile Datasheets are not publicly available and i haven't had a chance to try this myself, so i don't really know for sure...
QUOTE 2. Assuming a lidless mobile athlon CPU pins are identical with a desktop 794 socket, would it be possible to set a lower voltage for each PState in the BIOS (is this even controlled by the BIOS?), or would you have to specify one voltage & multiplier setting at bootup?
Both mobile and desktop A64's do use the same 754-pin Socket and are mechanically compatible.
P-States, however, CANNOT be altered to my knowledge - they're fixed values for each CPU.
If you set your multiplier/voltage to 'auto', it'll most likely boot at either the minimum or maximum multi/voltage, although the voltage might not be detected properly(atleast the mobile AXP-M used a slightly different VID-scheme than its desktop-counterparts, so this *might' be similar for the mobile A64).
Once you specify a different multiplier and/or voltage in BIOS, that should be what the processor will boot at(provided the multi is equal to or lower than the CPU's default/maximum).
QUOTE 3. Would it be possible to programmatically change the CPU's PState on the fly based upon its current load, or is this something that occurs below the operating system level?
Other than making use of the C'n'Q feature(which might be limited with mobile parts), i don't think an automatic, load-based adjustment is possible...
However, you should be able to manually change both multiplier and voltage in window$ using a utility like CrystalCPUID or CPUMSR.
QUOTE 4. Has anybody else tried this or heard of why it would or wouldn't work?
Even tho i haven't tried this myself, i'm pretty sure a mobile Athlon 64 would work in a desktop motherboard without much problems.
I've read about atleast one or two people who successfully tried this - they're overclockers, tho, so i don't know about PowerNOW!-capabilities when using a mobile A64 in a desktop board.

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