video or board bottleneck?

[wolfbite_aus]

Hi all,

Trying to work out where my bottle neck is (or if I even have one)

I have a nvidia 6800gt video card
and a ga-7n400 pro2 board

how do you work out if there is a bottle neck or not?
ie is the board too slow for the video (or the video for the board)

so as I can work out what to upgrade (dont mention sli please

This is probaly the one MAIN area thats never been explained (in reasonably simple terms, or calculation)

Thanks

[NeddySeagoon]

wolfbite_aus,

Under what conditions do you need to know about potential bottlenecks ?
For word processing you won't have a problem, nor for other 2D applications.

For 3D applications ...
You also need to tell us about your PCI-E or AGP set up.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

[wolfbite_aus]

agp 8
12000 glxgears
about 42-24 frames for ut2k4

reason I think bottleneck
old video card g4 4600
almost same stats for ut2k4
but think 6000 or 8000 got glxgears

could be processor too maybe?

what I WOULD like to know is
how to work out what the throughput from the video card and the mboard should be
and see if thats a bottleneck or its elsewhere (cpu?)

[Vulpes_]

The ga-7n400 pro2 board is S462 platform, of which the 6800GT far more overshoots. The main bottleneck here is the CPU, for the 6800GT, it is simply not powerful enough. To use the full potential of your card, you should upgrade to P4, or, and IMO this latter choice is the better one, to an Athlon64 platform.

[wolfbite_aus]

gathered that that might be the case

But also would like to know how to do the maths

ie how much throughput possable on mboard and vboard

must be a way to see it in numbers.

anyone know the maths?


no go with p4
will be amd 64

any recommends on which chip & board?

[Vulpes_]

I doubt that someone will come and say: "If you upgrade to X, then your video performance will rise Y times.", because this highly depends on what software you use, and how you use it. Deducted from the 6800GT, I suppose you are a gamer, therefore you can mainly operate with filters and resolution. As of chip&board, it is up to you. If you plan to keep your VGA, then only an AGP system is possible, so Via K8T800 Pro and nVidia nForce3 Ultra boards are the most common choices, maybe the latter one if you plan to overclock. BTW, to ensure smooth gaming, have at least 1 GB RAM.

[NeddySeagoon]

wolfbite_aus,

The maths isn't difficult to calculate what the various limits are but getting the data to know what the real life bottleneck is, is the hard bit.

Lets start with a 32 bit 33MHz PCI bus. It has a maximum theroretical bandwidth of 133MB/sec.Its a total waste of time putting a 1Gb/sec network card there because the PCI bus cannot provide the data rate.
A hard drive is limited by how fast bits can be read/written to/from the platter. This is related to the speed of the platter under the head, which is greatest near the outside. Many years ago, HDD had a fixed number of sectors per track, so this was ignored. Today, they are zoned, tracks near the outside hold more data than tracks at the centre.
Lets settle on a sustained data rate of 50MB/sec for a HDD.

It can been seen that a HDD transferring data at its sustained rate is about half a PCI bus full.

The AGP bus is a cut down PCI bus, so only two devices are permitted. It has some speedups like a 66MHz clock, not 33MHZ and 8x transfers. In theory, that makes it PCI x 16.

Memory bandwidth is much more complex because of latencey and burst transfers. Applications can easily defeate the usefulness of the burst modes too.

Which of the above are bottlenecks varies from application to application. As a live example, take seti@home.
It makes very little use of the HDD or the network but does lots of floating point calcualtions over a 16Mb deta set, so it won't fit into cache memory. This makes it memory bandwidth limited. Anything else that takes up memory clcyes slows it down.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

[Vulpes_]

[NeddySeagoon]

Vulpes_,

You need some bandwidth for the handshaking in the reverse direction. A 1GBit NIC can do full duplex so thats 250MB/sec on the bus if you want to support it flat out both ways.
Further, the 133MB/Sec on PCI is the theoretical maximum, assuming you use bursting for all transactions. You can't do this in practice.
_________________
Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

[Vulpes_]

Sure, I was thinking about a Half Duplex transmission, not Full Duplex, and talking about bus limitations, not practical applications.