First Cell demo (48 MPEG 2 Videos)

[randycat99]

You are going to find that extrapolation makes for pretty shaky foundation. At some point you are going to either blow out the cache or the bandwidth of that cache by scaling to x amount of streaming videos on that P4 example. Then your actual gains will top out pretty drastically and the extrapolation will be left hangin in the wind.

As an example, a single command line SETI will run pretty fast on that P4. It may actually scale fairly linearly up to 10 simultaneous SETI's. ...but 12 may break from that trend, and by 15, things seem to be crapping out (and major cache thrash, in progress). You get the point.

This really will separate the "thin pipe, big cache" from the "big pipe, small cache" scenario (except this time it's more like a "big pipe, big cache" type of situation). One's going to top out and the other is going to scale linearly quite a bit further out.

 

[ERP]

OK but all you really need to do to resolve the issue is to change your work pattern.

Say decode 1 second of each stream before swapping so that you get the value of the cache before it ends up being flushed.

Running multiple copies of an application on windows versus a custom written demo application is a stupid comparison anyway. The former is always going to have problems with cache management because the OS is optimised for user experience not running multiple copies of media player.

I wouldn't want to predict how fast a reasonably clocked P4 could do something similar in an similar environment, but it certainly wouldn't be the order of magnitude slower a lot of people seem to be implying.

We don't even have a good idea what the limiting factor was? It could just as easilly been read bandwidth as opposed to CPU cycles.

 

[nAo]

I don't know how many DVD movies can a P4 play at the same time, but I have no doubt CELL could AT LEAST manage that figure multiplied by 10 (and
imho this is a very conservative figure).
A lot of people is assuming Toshiba CELL demo was completely tax the system, well, I don't think so

 

[V3]

According to Toshiba they could have decode more than 48 streams. Its just a demo you know.

And comparing it to dual 3.5GHz P4, its not how many streams that's interesting but how does the wattage and how hot the two chips compare.

 

[Ty]

Running multiple copies of an application on windows versus a custom written demo application is a stupid comparison anyway.

<snip>

I wouldn't want to predict how fast a reasonably clocked P4 could do something similar in an similar environment, but it certainly wouldn't be the order of magnitude slower a lot of people seem to be implying.

Exactly what I was leading to. That it's a silly comparison since we really can't see under the hood as well.

 

[AlNom]

heh.


48 streams isn't enough for my porno.

But who watches 48 things at once? Can we get a more useful demo please?

 

[PC-Engine]

Running multiple copies of an application on windows versus a custom written demo application is a stupid comparison anyway.

<snip>

I wouldn't want to predict how fast a reasonably clocked P4 could do something similar in an similar environment, but it certainly wouldn't be the order of magnitude slower a lot of people seem to be implying.

Exactly what I was leading to. That it's a silly comparison since we really can't see under the hood as well.

But ERP just said a P4 wouldn't be that much slower in that same specialized situation. We already have two programmers basically saying the same thing.

Anyway the reason why I brought up Windows was to get a worst case scenario. The P4 in the same specialized demo environment would be able to perform even better like ERP said.

Like I said before, 48 SD MPEG2 streams for CELL is certainly impressive, but it doesn't seem to be to be orders of magnitude better than current PC tech.

I agree.

 

[London Geezer]

heh.


48 streams isn't enough for my porno.

But who watches 48 things at once? Can we get a more useful demo please?

Cable/Satellite TV? Instead of browsing, you have a page with "a lot" of channels all playing properly at once, so u can select what you want to see...
But there are other technology limitations that would make that quite hard anyway.


Nothing to do with PS3, but this was a Cell demo, not a PS3 demo...

 

[Ty]

But ERP just said a P4 wouldn't be that much slower in that same specialized situation. We already have two programmers basically saying the same thing.

The difficulty and thus pointlessness is in making a valid comparison in the first place.

Anyway the reason why I brought up Windows was to get a worst case scenario. The P4 in the same specialized demo environment would be able to perform even better like ERP said.

That wouldn't be a worst case scenario. Far from a best case but not the worst case either.

I don't think anyone said it was orders of magnitude better.

 

[PC-Engine]

But ERP just said a P4 wouldn't be that much slower in that same specialized situation. We already have two programmers basically saying the same thing.

The difficulty and thus pointlessness is in making a valid comparison in the first place.

Anyway the reason why I brought up Windows was to get a worst case scenario. The P4 in the same specialized demo environment would be able to perform even better like ERP said.

That wouldn't be a worst case scenario. Far from a best case but not the worst case either.

I don't think anyone said it was orders of magnitude better.

Of course the comparison isn't 100% valid. That wasn't the point which you obviously don't get.

The programmers understand but you don't.

 

[Apoc]

1080i ATSC MPEG2 on this single processor non-HT 2.53ghz/533mhz FSB machine, and I'm averaging about 33% CPU load.

How do you do that? I have an Athlon XP2200+ and 1080 video chugs like hell in my machine. I have a 9700 pro (9500 softmodded) btw.

 

[aaaaa00]

1080i ATSC MPEG2 on this single processor non-HT 2.53ghz/533mhz FSB machine, and I'm averaging about 33% CPU load.

How do you do that? I have an Athlon XP2200+ and 1080 video chugs like hell in my machine. I have a 9700 pro (9500 softmodded) btw.

Which MPEG2 codec are you using?

 

[PC-Engine]

Ok, I have confirmed that MPEG2 decoding scales roughly linearly on this PC at least.

I got ~20% CPU usage with one stream, so I built a DirectShow filtergraph with various numbers of MPEG2 streams, output to the default Video Render. No audio decoding, though I suspect that would be minimal additional CPU load.

Remember this is a far from state of the art machine: only a single 1.4 ghz P4, 256KB L2 cache, no HT, only 400 mhz FSB, no DDR memory, no fancy PureVideo acceleration.

1 stream = ~20% CPU
4 streams = ~ 80% CPU
5 streams = CPU pegged.

You could tell at 5 streams the machine was starting to struggle to keep up, you would occasionally get dropped frames when something running in the background would kick in and suck away some CPU cycles.

One other thing is that Windows XP doesn't have multimedia I/O prioritization, nor are there processor reserves or any of that realtime stuff, so there's no way for the OS to prevent background apps from causing a frame drop when the system is running flat out like this.

Assuming you remove the OS from the equation, and run the MPEG2 codecs bare metal on the CPU directly (no background thread scheduling, no random I/Os from system services), I bet you could squeeze out some more from this CPU, or at the very least make 5 streams run perfectly.

To be clear:

48 SD MPEG2 streams is impressive. I don't think you can currently build a non-exotic PC that can do that. However, that said, it doesn't seem so far out of reach for near-future, or even current PC tech to match.

To be doubly clear:

I'm not suggesting that the demo showed CELL's maximum performance.

Thanks for doing that experiment aaaaa00. At least now we have a very good idea of what could be achieved without using Power DVD and multiple windows.

Considering a P4 is more general purpose than CELL, it really puts everything into perspective now.

 

[London Geezer]

I know this has nothing to do with consoles, but why is it that when i try to open more than one video (any video, pretty much), the second one goes all green and is, to put it simply, fucked? Basically i can't have more than 1 video playing at any one time. Thing is, i'm sure i used to be able to do that up until last year, cause i tried and it worked fine...
Is it a drivers thing?

 

[Apoc]

1080i ATSC MPEG2 on this single processor non-HT 2.53ghz/533mhz FSB machine, and I'm averaging about 33% CPU load.

How do you do that? I have an Athlon XP2200+ and 1080 video chugs like hell in my machine. I have a 9700 pro (9500 softmodded) btw.

Which MPEG2 codec are you using?

Ah, well, MPEG2, i guess I have to read better. I was refering to 1080 WMV-HD.

 

[Shifty Geezer]

Why is this topic still being thrashed as a Cell performance demo thing? It's already been stated it was a Toshiba software platform demo. People ought to be discussing whether Cell looks easy to program or not (SPE allocation is not a programmer responsiblity in this example.)

 

[London Geezer]

Errr... Help?

I know this has nothing to do with consoles, but why is it that when i try to open more than one video (any video, pretty much), the second one goes all green and is, to put it simply, fucked? Basically i can't have more than 1 video playing at any one time. Thing is, i'm sure i used to be able to do that up until last year, cause i tried and it worked fine...
Is it a drivers thing?

 

[nAo]

If CELL is so damn slow that a couple of P4s can match its performance whilst
it's playing a DVD and since Xbox360 is expected to be way slower than CELL ..we can assume Xbox360 is doooomed by a single P4, LOL
Obviously I'm kidding , but all this discussion is getting ridicolous

 

[AlNom]

Cable/Satellite TV? Instead of browsing, you have a page with "a lot" of channels all playing properly at once, so u can select what you want to see...
But there are other technology limitations that would make that quite hard anyway.

There's a similar function in my tv to doing that (updates only one channel at a time), but it's much faster to just use the digital tv box to scroll through what's on than watching 48 streams to pick out what I want. Plus, I don't know about splitting a <40" tv into 48 sub pictures. It's kind of... "useless" IMO.

Now, if it were processing over the internet streaming video... video conferencing would be pretty crazy.... kinda like a much bigger version of Carver's own conferencing in Tomorrow Never Dies, only real people use two hands to type.

Anyhoo... this shouldn't be in the console forum if it's not about a console demo (as you've pointed out before).

 

[a688]

Errr... Help?

I know this has nothing to do with consoles, but why is it that when i try to open more than one video (any video, pretty much), the second one goes all green and is, to put it simply, fucked? Basically i can't have more than 1 video playing at any one time. Thing is, i'm sure i used to be able to do that up until last year, cause i tried and it worked fine...
Is it a drivers thing?

Its not a drivers thing, its a codecs thing. You probably have multiple codecs that can play the same file and are fighting one another. Have you installed any codec packs?