[SDL] single pixel drawing

Atrix Wolfe Atrix2 at cox.net
Wed Jul 17 11:40:01 PDT 2002


im glad people still pay attention to these things (:

----- Original Message -----
From: "Jacek Wojdel" <wojdel at kbs.twi.tudelft.nl>
To: <sdl at libsdl.org>
Sent: Wednesday, July 17, 2002 2:50 AM
Subject: Re: [SDL] single pixel drawing


> On Tue, Jul 16, 2002 at 11:18:36AM -0700, Neil Bradley wrote:
> > > They are much less expensive than they used to be, but
> > > Multiplies are still more expensive than adds, and you
> >
> > How so? At least on the Pentium, Multiplies are 1 clock or less, just
like
> > shifts.
>
> But since Pentium Pro you can issue two instructions per cycle. Those can
be
> 2 adds, 1 add and 1 shift etc. You cannot however issue more than one
> multiplication and it blocks both ALUs. Moreover shifts and adds have
> latency of 1 cycle, while multiplication has latency of 4 cycles. In
total,
> if you have shift+add it will execute in between 2 and 4 cycles, while
> mul+add will execute in between 5 and 7 cycles. That's twice the
> performance.
> Cheers,
> Jacek
> --
> +-------------------------------------+
> |from: J.C.Wojdel                     |
> |      J.C.Wojdel at cs.tudelft.nl       |
> +-------------------------------------+
>
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