Subject: Re: Port of NetBSD to XScale
To: Charles M. Hannum <root@ihack.net>
From: Ignatios Souvatzis <is@netbsd.org>
List: port-arm32
Date: 03/29/2001 22:06:01
On Thu, Mar 29, 2001 at 11:45:39AM -0800, Charles M. Hannum wrote:
>
> On Thu, Mar 29, 2001 at 11:42:40AM -0800, Charles M. Hannum wrote:
> >
> > On Thu, Mar 29, 2001 at 11:08:13AM +0100, Richard Earnshaw wrote:
> > > >
> > > According to the documentation I have, Xscale only predicts B and BL
> > > instructions, both of which only have pc-relative invariant offsets. Any
> > > mis-predicted (or unpredicted) branch takes at least 5 cycles to issue (8
> > > if the value has to come from memory). [XScale Developers Manual, Table
> > > 14-4]
> >
> > So a function return always takes 5 clock cycles?? Was this thing
> > developed by the same group that did the P4, perchance??
>
> Shit, and another 5 cycles for every PIC function call. This is gonna
> suck a lot.
Maybe they want to make sure it is only used for embedded applications, not
for general OSes.
Regards,
-is