Mac and PCs graphic speeds (was: Ken Burns Effect in Rev?)

Sat May 14 09:15:42 EDT 2005

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I'd bet it's more related to the graphics architecture of the platform 
than the graphics cards themselves.

Mac OS X's Aqua interface is drop-dead gorgeous, and very easy (and 
fun) to work with, but that comes at a price.  All of the transparency 
effects, multilayer compositing, PDF-style graphics architecture (not 
very well used by Rev, BTW), and so forth -- all adds up in terms of 
processing cost.

OTOH, the relatively simplistic (from a processing perspective, at 
least) Windows GDI architecture makes less demand on both the processor 
and the graphics card, meaning faster apparent performance.

It's not that the cards on the Macs are slower, but rather that they 
have more work to do to achieve similar results.

Now there is another trick involved here, which relates more to the 
underlying architecture of the operating systems.  Speed isn't 
everything.

When early versions of Windows NT were first designed, the graphics 
system was running as a user-mode "application" of sorts on top of the 
Windows kernel.  This helped to isolate the graphics system somewhat 
from the low-level kernel code, theoretically improving system 
stability and scalability.  However, this kind of architecture implies 
that programs need to establish interprocess communications routes with 
the code implementing the graphics system.  This communication adds 
overhead to the system, which slows down performance.

With the release of Windows NT 4 (I think it was that version, could be 
wrong), the graphics system was moved into the kernel (M$ may argue 
that it was moved into the "executive" and that the kernel is something 
different, perhaps on a block diagram that may be true, but from the 
computer's perspective they are two parts of the same thing).  This has 
the effect of substantially reduce the overhead involved in accessing 
the graphics system by allowing calls to the graphics system to pass 
through from the app to the graphics system without the extra 
manipulations required to get that data to another app.  This helps to 
make the Windows graphics architecture one of the *fastest* ones around 
- -- but this also comes at a cost.

Placing the graphics code in the kernel adds complexity to one of the 
most important parts of the operating system.  This added complexity 
makes maintenance more difficult, promotes decreased stability, and 
makes it harder to recover when something goes wrong.  It also has a 
nasty effect on security:

Kernel-level code can access any part of the computer system.  An 
exploitable bug in that code could give someone complete access to the 
entire computer system.  With so much code in the kernel layer, Windows 
is a security risk no longer waiting to happen (just look at all of the 
viruses and so forth which have hit the news for Windows -- and that's 
just for starters).  The less code in the kernel, the easier it is to 
verify absence of such security holes, and the easier it is to enforce 
security on the system (note that this assumes all else being equal -- 
an incredibly good kernel running underneath horribly pathetic software 
will not make that software secure by any means).

Microsoft has this nasty habit of increasing performance by moving lots 
and lots of code into the kernel.  This increases speed, and yes, 
Windows is very, very fast (it has to be to get away with running on 
relatively poor hardware).  But that speed is at the expense of 
stability and security.

Mac OS X, on the other hand, has an extremely small kernel, much 
smaller than most.  The graphics system and so forth are running as 
userland processes, much as the graphics system was originally designed 
to under Windows NT.  This means lower performance, but it helps to 
improve stability and security on the system.

So in other words, OS X gives up some of the cheap-thrill speed of the 
Windows architecture in order to help protect its users from the 
security and stability issues which are so rampant on the Windows 
platform.

It's a design choice.

On May 14, 2005, at 5:43 AM, Eric Chatonet wrote:

> Hi Richard,
>
> Working with both Macs and PCs, I am always surprised by the BIG 
> difference between graphic cards speeds.
> I have to say that graphic cards on Macs are very slow compared to 
> even cheap PC cards...
> For instance, you use a dissolve effect FAST on a Mac since it appears 
> too slow without adding fast.
> Then you put the stack on a PC and you don't see nothing: It's already 
> too fast :-)
> All visual features where a delay can't be set (as for the move 
> command) have to be changed according to the platform.
> Some of them can't be used on Macs: everybody does not own a G5 2*2.7 
> GHz :-(
> BTW Chipp's stack works great on any PC...
>
> Best regards from Paris,
>
> Le 14 mai 05, à 08:12, Richard Gaskin a écrit :
>
>> Chipp Walters wrote:
>>>> try in the message box:
>>> go URL "http://www.gadgetplugins.com/chippstuff/KBmain.rev"
>>
>> I apppreciate your putting that together, but alas on my 1GHz Mac 
>> it's fairly choppy.  :(
>> Does it look smooth on your machine?
>
> Amicalement,
>
> Eric Chatonet.
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- -----------------------------------------------------------
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$ true | cat /usr/manual | grep "John 3:16"
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