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Re: bcm33xx port

To: Luke -Jr <luke@dashjr.org>
Subject: Re: bcm33xx port
From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: Mon, 9 Jun 2008 08:40:57 +0200 (CEST)
Cc: "Maciej W. Rozycki" <macro@linux-mips.org>, linux-kernel <linux-kernel@vger.kernel.org>, linux-mips@linux-mips.org
In-reply-to: <200806081836.42351.luke@dashjr.org>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <200806072113.26433.luke@dashjr.org> <200806081527.31221.luke@dashjr.org> <Pine.LNX.4.55.0806082249330.15673@cliff.in.clinika.pl> <200806081836.42351.luke@dashjr.org>
Sender: linux-mips-bounce@linux-mips.org
On Sun, 8 Jun 2008, Luke -Jr wrote:
> On Sunday 08 June 2008, Maciej W. Rozycki wrote:
> > On Sun, 8 Jun 2008, Luke -Jr wrote:
> > > >  Not exactly.  Try harder -- this is simple arithmetic and you've got
> > > > all the data given above already. :)
> > >
> > > 200 / 2? I'm not really sure what a 'jiffy' is..
> >
> >  Hmm, I have thought it can be inferred from the code involved or failing
> > that -- Google...  Well, anyway, a jiffy is a tick of the kernel timer or,
> > specifically in this context and to be more precise, the interval between
> > such two consecutive ticks or, in other words, 1/HZ.
                                                     ^^
Look at CONFIG_HZ, which is probably 100, 250, or 1000.

> jiffy = 1 / 200000 HZ = 0.000005 sec/tick
> loop = 200000 instructions / 2 instructions per loop = 100000 loops/sec
> 
> So 0.00000000005 loops per jiffy? But it can't be, since loops_per_jiffy 
> isn't 
> floating point... :/

So loops_per_jiffie is approx. CPU clock frequency / CONFIG_HZ.

Gr{oetje,eeting}s,

                                                Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                                            -- Linus Torvalds

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