timmala

Why are some processors "underclocked"?

Why are some processors listed as 1GHz "underclocked" to 800MHz for example?

Most Useful Answer blizzard7  Oct. 24, 2011 at 11:46

:)

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MDrX  Oct. 24, 2011 at 10:48

Faster (newer) processors are generally more efficient so they are usually underclocked to give comparable performance whilst reducing heat and extending battery life.

So an 800MHz CPU running at 800MHz will drain battery quicker, produce more heat and probably die sooner than a 1GHz CPU clocked at 800MHz.

Newer processors could well be cheaper, too. It makes sense for Apple to use the same CPU in the iPad, iPhone and Touch and underclock them as necessary for decent battery life gain.

blizzard7  Oct. 24, 2011 at 10:48

Newer processors are said to do more work per clock cycle, so for instance a 3 GHz Pentium 4 (D) will get its butt kicked by a 3 GHz Core i5. So overclocking an old CPU wouldn't give you as much of a boost as using a new one and overclocking can also raise the heat produced and power consumption.

However, the new CPU may only come in a single variant so it'd make sense to just buy it then underclock it, to the heat and power usage they need. In the example of Apple, it seems like it's just using a variant of the iPad's processor underclocked, which makes sense because the iPad is a much larger device with better cooling and battery power.

blizzard7  Oct. 24, 2011 at 10:54

@MDrX
Not quite sure I get your second paragraph. If that were the case, why doesn't Intel just make a 10 GHz CPU and underclock it to 4 GHz.

MDrX  Oct. 24, 2011 at 11:29

Hmm, not very well worded.

'So an older 800MHz CPU running at 800MHz will drain battery quicker, produce more heat and probably die sooner than a newer 1GHz CPU clocked at 800MHz.'

blizzard7  Oct. 24, 2011 at 11:46

:)

CTPAHHIK  Oct. 24, 2011 at 12:16

Manufacturing defects also play significant part. You make 1Ghz CPU but it's unstable at that speed, but works fine at say 900Mhz. Instead of throwing it out; re-badge it as 800Mhz and sell it.

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