> Sender: squeak-dev-bounces at lists.squeakfoundation.org
> From: Yoshiki.Ohshima at acm.org
> Date: Tue, 20 May 2003 01:11:28 +0900
> To: The general-purpose Squeak developers list
> <squeak-dev at lists.squeakfoundation.org>
> Subject: Re: XScaled Squeak
> -----

>
>   I don't think you can turn it on from a user program...  (What do
> you mean by "WinCE's lack of security"?  It is at least memory
> protected, separated supervisor/user mode OS.  The reference manual of
> XScale lists the sample code to change the cache behaviors and memory
> region attribute flags or such, but as far as I understand (with a
> little experiment), The instruction cannot be executed from a
> user-level program.
>

WinCE has little if any real security....  If it had any, it would be
more difficult for us to replace the bootloader that comes with WinCE
with the one that we use for Linux (we overwrite the boot sector in flash....

I'm not familiar with the details; folks down the hall from me are.


>   Of course, my attempt might have been too easy...
>
> > This isn't true for Linux on the iPAQ, but as Linux on the iPAQ 54xx
> > is still a "work in progress", it returns you to the previously
> > unsolved problem.  We do have H39xx's running pretty completely under
> > Linux (the first models with the XScale processor), however, and if you
> > have a unit with the fixed cache, we take advantage of it.
> > We hope H54xx's will be done in another month or two:
> > the kernel boots fine, and we're working on the device drivers.
>
>   Oh, do you mean that there are some (stepping of) chips with the
> fixed cache and named PXA250??

I believe so, and I believe they went into production a month or two
ago in the iPAQ's.  Whether they changed the numbering or not, I dunno
(it may very well be called the 255).  I'm not an expert at this level
of things as others do the base system for me :-).

>
>   As for the Squeak performance, there is another twist in this story.
> The VM on SL-C700 (a PXA 250 device) feels much faster than other PXA
> 250 based WinCEs (Aaron has reported similar with his machines...)
> There might be some performance glitch in the VM support code.  The
> toolchain that Sharp provide is based on 2.95.2 and I don't think it
> does XScale specific optimization.  If we change the compiler, it may
> get some boost.

Yes, you want a more recent toolchain to get the best performance out
of XScale; the calling sequence, for example, really wants to be different
to get good performance out of it.

We have such toolchains available.

>
>   The coming PXA255 based SL-C750/C760 may perform somewhat better
> than C700.  This machine is really interesting to see.  (Actually, you
> can try it at a Sharp showroom in Tokyo today...)
>
>   Also, using GCC for builidng WinCE VM, if it is possible, might
> help.

You certainly want the proper toolchain for the PXA.  Phil Blundell or
Jamey Hicks would be the person to ask about exactly what toolchain
to use to build for it using GCC.

                              - Jim

--
Jim Gettys
Cambridge Research Laboratory
HP Labs, Hewlett-Packard Company
Jim.Gettys at hp.com