[mythtv-users] S-video/nvidia problems

[Brian Wood]

On Sunday, August 08, 2010 05:47:12 pm Tortise wrote:
> ----- Original Message -----
> From: "Brian Wood" <beww at beww.org>
> To: "Discussion about mythtv" <mythtv-users at mythtv.org>
> Sent: Saturday, July 31, 2010 4:19 AM
> Subject: Re: [mythtv-users] S-video/nvidia problems
> 
> On Friday, July 30, 2010 09:46:23 am Eric Sharkey wrote:
> > On Fri, Jul 30, 2010 at 11:27 AM, Brian Wood <beww at beww.org> wrote:
> > > On Friday, July 30, 2010 09:07:28 am bhaskins wrote:
> > >> IMHO YMMV shared memory is a nasty performance hit.
> > >> I have added video cards to several systems and the users have often
> > >> said it was like
> > >> getting a new box.
> > > 
> > > Do you think this is due to RAM being taken away from the system, IOW,
> > > if you add extra RAM to make up for what the video system is using
> > > would it be the same as if you were using a discreet card?
> > > 
> > > Or is it due to the video system not performing as well with shared
> > > RAM, as with a card, perhaps due to the RAM on the card being faster
> > > than the system RAM?
> > 
> > As far as I understand it, the bottleneck is the bus that connects the
> > RAM to the rest of the system.  When video ram is shared with system
> > ram, both the CPU and the GPU compete for time to do reads and writes
> > to RAM on the same bus.  When the GPU has its own RAM, that contention
> > goes away.
> > 
> > Because of that, you can't improve the situation just by adding more
> > ram, you need to add another bus, which isn't possible.
> >
> >That's what I figured, thanks for the confirmation.
> >
> >So using integrated video slows the entire system down, as well as not
> >giving the same graphics performance.  I guess the
> 
> only time integrated graphics makes sense is if the
> size/weight/heat/power/cost savings are worth the performance hit to you.
> If the result is "good enough" for you then it makes sense.
> 
> >Even if you have no need for high-performance video (say an office
> >environment), it still might pay to have a discreet video
> 
> card, which would give you the effect of a CPU upgrade.
> _______________________________________________
> I'm not convinced, I think the devil's in the detail and that most
> integrated video is low end budget oriented.  Would this be said about the
> Revo boxes?  (I don't have one, but I doubt it)  My experience of Dell
> Latitiude D830's with built in (vdpau a grade) video is they work fine in
> practice (respecting the theory).  (256M pure video RAM and 256M borrowed
> system RAM).  I presume we are talking about the same things here?

I think in many cases integrated video is in fact "budget oriented", but in some cases the GPU chip integrated onto the 
motherboard is the same chip as is used in some discreet graphics cards.

The Revo's "ION" graphics is, I believe, just a 9400M chip, "ION" is marketing speak.

So you  take a performance hit due to sharing the same bus between graphics and other things, but the chip may well be a 
high-performance featureful chip.

There are many reasons for wanting to integrate graphics onto the mobo, cost is one of them, but size, power, weight and 
heat are others.

Buying a system with more graphics power than you really need is just as silly as buying one with less than required. If 
you can accomplish the mission by spending less, it makes no sense to spend more.