Re: Stock IA64 kernel on SGI Altix 350

[Linus Torvalds]

On Fri, 4 Jun 2004, Jan-Benedict Glaw wrote:

> On Thu, 2004-06-03 22:09:06 +0200, Jan Kasprzak <kas@xxxxxxxxxxxxxxxxxxx>
> wrote in message <20040603200905.GA27701@xxxxxxxxxx>:
> [ia64 booting]
> > CPU 1: base freq=200.000MHz, ITC ratio=14/2, ITC freq=1400.000MHz+/--1ppm
> > Calibrating delay loop... 16.44 BogoMIPS
> 
> Hihi:) A ~ 55MHz VAX does nothing with about 15 BogoMIPS.

Yeah, the bogomips have become too bogus to even be useful these days.

Just as a clarification, "bogomips" is really "bogo-timing-events-per-
second-multiplied-by-two" (aka "bogotepsmbt").

The "timing event" used to be a "two-instruction loop", which is where the 
"multiplied-by-two" comes from: at that point the "bogotepsmbt" becomes 
the number of instructions per second, and that explains the "mips" part 
of the name.

But since it's really used for timing small delay loops, and since the
two-instruction loop wasn't very good at that (due to power-usage, SMT
issues, frequency changes, you name it), the implementations have sadly 
started to drift away from using instruction retire as the event they 
count, and start using a separate counter instead.

So 16.44 BogoMIPS these days really implies " ~8MHz timer frequency ".

The timer is a lot better from a technical standpoint, but it sure is a 
hell of a lot less entertaining than the original MIPS thing..

			Linus
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