Do you know about CPU Halt and Grant Idle states? Almost any modern operating system will enter these states as soon as CPU usage drops below
100%. This isn't some setting in a property page somewhere, it happens automatically whenever CPU usage isn't 100%.This isn't an operating system Standby or Suspend state, where it blanks the screen. It is an instantaneous and effective power reduction mechanism that is instantaneously reversed as soon as CPU is required.
Christian.
I haven't managed to find any recent figures on AMD/Intel websites, but they must be on there somewhere.
I've found approximate figures for previous generation processors which suggest that consumption drops from around 20W to 3W when the processor is in an idle state. Unfortunately, the source is less than bomb proof.
Christian.
There used to be a tool to disable/enable the idle states in some AMD processors. Temperature sensors built into many motherboards can show that when the IDLE command was disabled, the temperature of the CPU rose and when the IDLE command was enabled, the CPU temperature dropped significantly. Of course, when something was constantly using the CPU (gaming etc) the CPU temp rose back up and stayed high until the CPU load dropped again.
Just as a pointer, if you're running NT/W2k/XP open up Task Manager, go to the 'Process' tab and scroll down to the "System Idle Process" process - and you'll see that generally, its 90% or so idle. As I'm typing this email I've got loads of IE windows open and OE is checking my email but the Idle Process is taking about 92-96% of the CPU - and this means that the machine is only using 4-8% CPU load yet its still displaying the screen and doing other things.
D
Every time.
BUT these states have to be explicitly coded into the BIOS etc. In all OS's I have designed or been aware of, the CPU at best sits in a tight loop waiting for some kind of interrupt from somewhere - most frequently the system timer. Then it probably rushes off to do a few timer related housekeeping tasks, nips round its scheduler to see if other interrupts have actually triggered the need to so timeslice code before going back to doing an endless loop or summat. I agree that a 'halt' instruction pending interrupt OUGHT to be used somewhere in the core OS..but is it? Not on my windows 98 I am sure.
Given the size of heatsinks on the CPU, and the fans, its pretty clear that they are pulling tens of watts no matter WHAT they are doing. I will grant and exception uin laptop cases. I am sure they do indeed have sophisticated power management circuitry, but I am pretty sure that this computer does not.
Especially if they're Linux ones (though I think the latest Windows OS' have discovered the IDLE instruction as well - or is it HALT?).
But you can HALT the processor when it's idle and it consumes very little power, Linux kernels do this as do the latest MS ones I believe.
PCs with AMD or Intel chips in, anyway.
Damn. Why do they have idle loops/processes/etc., then?
:o)
This has nothing to do with the BIOS. BIOSes are a PC-ism, anyway.
The kinds of functionality we are talking about here takes place "below" the O/S level (not that W/98 is much of an O/S in the first place). (Despite my earlier facetious remark about O/S idel loops...)
Not one at all AFAICS. A monitor maybe, and not a particularly good one. A house built on sand? Definitely. OS? Nope. May it rest, finally, in peace.
.andy
To email, substitute .nospam with .gl
Nothing except internal machine codes takes place below operating system level.
Its necessary for the OS to call 'halt' or 'idle' or whatever, and wait for interrupts to restart the CPU.
But from Cambridge that's a BA + a wait of a few years after matriculation, innit?
-- Richard Sampson
email me at richard at olifant d-ot co do-t uk
No offence, but you obviously have no idea what you're talking about. Can I suggest you go and read about the IBM S/360 and Transmeta processor architectures?
And £35.
Yes, but teh BA course is of MA standard.
Was it? Don't remember. I think thats only if you bother to attend the jolly.
Frankly, I'd rather not.
All processors are CPU, varous hardware bits and microcode. The OS core is ultimately in machine code, and the microcode interprets that and fiddles with the actual hardware.
Sop below OS is only the microcode.
>
Dunno. My degrees are from, er, newer establishments.
Probably wise.
Well, sort of. But I think we've wandered far enough from the original point. And unless you have a fab in your garage, it sure ain't DIY.
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