C7xxx vs Yopy - speed differences.

[nilch]

I was reading this review
http://www.linuxjournal.com/article.php?sid=6933
and the reviewer mentioned that the Yopy is faster than the C7xxx series software wise, because as he says

\"Why is the Yopy faster than a C700 even though it has a slower CPU? The answer lies in the software. Unlike the Zauruses and the Simpad, which are based on Qtopia/OPIE, the Yopy uses the X Window System and the mobile GNOME environment.\"

I find this strange, since Qtopia was supposed to me leaner (and hence meaner and faster) than the X11 environment.

Is this true ?
If yes, this might infer that the X11 ROM for the Zaurus will be faster than the Qtopia based Sharp ROM too.

Whats the common knowledge on this ?

[TimW]

I have an Agenda (44MHz MIPS IIRC) which runs FLTK on top of X11 and, of course, the Zaurus. Its pretty clear that the FLTK/X11 configuration is a lot kinder to the CPU than Qtopia. I think the Psion Linux project has found similar results when comparing X11 with a lightweight window manager compared to Qtopia (Qtopia is, I believe, almost unusable on the Psion).

OTOH I don\'t know how QT/X11 will compare to QT/embedded. I suspect that the overall code size is somewhat smaller as you only need to emulate a subset of X11 to get QT/embedded going. I think some of the Opie people have tried QT/X11 on the ipaq. Maybe its worth asking on the opie forums?

[tumnus]

The C700 has the buggy PXA-250 CPU, which even though it is supposed to run at 400MHz, runs more like 200MHz. Now the C750/760/860 all use the PXA-255 which really does run at 400MHz and would surely be faster than the Yopy.

[nilch]

So you think the speed difference has more to do with the hardware (processor) than with diferences in the software platform ?

What are the benchmarks between Qtopia and X11 based ROMS on the Zaurus itself ? Any such tests done as yet, even though I understand the X11 is still in development stages now.

[TimW]

I think he (the reviewer) was including the SL5x000 devices (which have the same processor as the Yopy) as being slower than the Yopy though he wasn\'t explicit. He was fairly specific that he thought it was the software rather than the hardware causing the Zaurus to be slow.

Of course, slow software on fast hardware (eg C860) won\'t be as bad as slow software on slow hardware...

[2devnull]

Remember Qtopia is another layer on top on X11 (maybe this is not the case) but like GNOME which runs on top of X11, removing an additional layer will make things much faster.

[tumnus]

The reviewer specifically mentioned the C700 when it came to the speed comparison. It sounds to me like the reviewer is biased and is trying to justity his own personal purchase. It\'s very subjective as to which is the better Linux PDA. The Zaurii and Yopy models all have their strengths and weaknesses.

[Stigger]

Remember Qtopia is another layer on top on X11 (maybe this is not the case) but like GNOME which runs on top of X11, removing an additional layer will make things much faster.

No Qtopia is akin to Gnome as a Desktop Enviornment but there is no X11 it talk directly to the framebuffer via qte

[nilch]

Tumnus
that is indded a point that the reviewer compares with the C700 - the slowest of the Zaurus breed. and the buggy processor makes speed comparison invalid there.

<quote>No Qtopia is akin to Gnome as a Desktop Enviornment but there is no X11 it talk directly to the framebuffer via qte</quote>

excatly thats what was the logic for me thinking Qtopia would be faster than GTK on X11 - the removal of one (fat) layer - the X11 layer.

[TimW]

It sounds to me like the reviewer is biased and is trying to justity his own personal purchase.

I can see why you might read that into the review but it is categorically not true. Have a look at who owns the domain which http://externe.net/zaurus/forum/ runs on.

I have seen Qtopia/QT embedded and an X11 based environment running on the same (slow) device and Qtopia *is* slower.

OTOH whether it is slow enough to matter on the faster devices is a different question and I suspect that on everything except the SL5* series and maybe the C700 the response time is not a problem. I do find on my SL5000 that it is a bit slower than is completely comfortable.

You also need to take into consideration how easy it is to produce apps for a particular environment and it is a lot easier to produce apps for Qtopia than it is for many other environments (that is at least partly why there are more apps for the Zaurus, or at least why I suspect it will stay that way). There is always a trade-off between functionality and performance and Qtopia (or at least QT) provides a lot of stuff which I find eases my job as a developer. If you decide to go for the extra functionality provided by Qtopia then it makes sense to remove the extra X11 layer, if you can.

So IMHO, Qtopia *is* slower but it provides so much extra that it is worth the penalty and once you get up to the faster devices the slowness doesn\'t matter any way.

[Mickeyl]

Qtopie and Opie are nowhere near being speed optimized. Using gcc3 images is a good start, using the forthcoming OZ kernel, Qt4 and Opie 2.0 will improve things further.