Re: [SeaBIOS] insn prefixes?

[Kevin O'Connor]

On Sat, Oct 02, 2010 at 11:39:06AM +0200, Avi Kivity wrote:
> On 09/30/2010 05:51 AM, Kevin O'Connor wrote:
> > On Wed, Sep 29, 2010 at 08:19:33AM -0700, H. Peter Anvin wrote:
> > > Yeah... big real mode is rather expensive in terms of the 66 and 67
> > >  prefixes you end up littering the code with just to be in the mode you
> > >  actually want.  Better then to load a GDT, flip CR0.PE, and go to a
> > >  32-bit code segment anyway.
> >
> > That brings up an interesting question.  Do you know if instruction
> > prefixes result in slower cpu execution?
>
> Is there really a performance problem in seabios?

No.  I was asking only out of curiosity.  Even if prefixes slow 16bit
mode, a normal SeaBIOS boot runs very little 16bit code.

-Kevin