Dual Head Clone affecting framerate?

[wiggo]

I have been having various problems with the 5.21 drivers (as everyone else has) and so I did a couple of reinstalls and the like (see my post under "My Q3 Test Demo Results ....on my G400/PD 5.21")

However, I then enabled Dual Head Clone and my q3demo1 fps dropped from 33.9 to ~23. Turning DH Clone off resulted in the fps going back to 33.9.

Is this a known side-effect of using DH?

BTW. I am outputing the DH signal to a TV via S-Video

[SteveC]

VSYNC on or off? If it's on, then you may be getting cut off at something like 50fps /2 which roughly gives your 23fps.
If it's Off, I haven't a clue.

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Cheers,
Steve

[wiggo]

Both with VSync on and off.

Does anyone know what the hell is going on?

[Ashley]

That's a pretty heavy hit, but Yes - of course, DualHead exacts a performance penalty. Its unavoidable.

[Zypher]

It does? I don't see why, if the other ramdac only reads the buffer in its own turn.

As long as the second monitor is the same resolution or smaller, and set to show the same output (program) then WTF?

Theres only one render, and the read only happens less than 100 times a second (framerate and/or display rate) which shouldn't be detectable at all. (from 166 million times a second, its peanuts)

Now if it was a game that uses both monitors, and different things on each id understand. But that game isn't.

[CrazyBee]

the second display is not hardware accelerated (at least so I have heard) yet.

also, you have to pipe the info inbetween the two processors which will take some of the overhead from the processor. also, with two displays, you will have half the texture memory (16meg each) which will also affect it as well.

it will probably get better in time with the driver releases.

[tiqq]

Hi CrazyBee !
Why should the second display use texture memory if it is not hardware accelerated ??

I thought the second display is only a scaled view of the primary. So all you need is yust some bandwith....

tiqq

[Buuri]

It's impossible for that kind of a feature not to affect the performance, unless the 2 units would be completely separate including having their own buses.
And still they wouold share the same AGP bus..

_
B

[Meek]

Well, who says the second port is "not accelerated". Of course it is. You would not get even 10 fps in Q3Atest with software...

But, seriously, I suppose it could effect frame rates because of race situations in accessing the memory, but I doubt the difference would be that big.

At least I have not seen any noticeable difference in 3dmark for that matter. (It does report that the refresh rate is 50 Hz, though)

VSYNC would explain this really nicely. Maybe this is another feature of the opengl of G400, forcing Vsync always with the clone feature on?

M.

[Ashley]

DualHead necessarily uses up bandwidth because there is no second ramdac on the G400 - that's why, e.g., there are caps on your max. resolution and refresh rate, and why you cannot adjust gamma on the second screen.

Two single heads are always going to be better than one dual head...

[WereWolf]

The G400 DOES have two ramdacs... one of them is a 300mhz one, and the other is a TV/CRT lower quality hybrid ramdac.

I think. :-)

[Kruzin]

The second RAMDAC is built onto the Maven chip.

[Jorden]

the second display is not hardware accelerated (at least so I have heard) yet.

Well, Crazybee, try out <A HREF="http://www.egerter.com/q2/prland.zip" TARGET="_blank">PRLAND</A> then and tell me how the second monitor gives such accurate EMBM if it's NOT hardware accelerated...

Jorden.

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[Zypher]

News Flash:

There are two ramdacs. The specs on website say so. OTHERWISE, you could not have the 2nd output to tv at a different refresh rate! This is why g400 tv-out owns, and most previousones suck, they synced your monitor to a crappy 50 or 60hz. HELL NO, I'll never go under 85hz again.

The agp means jack shit for dualhead. The second output reads the g400 memory (which is on the card) with an internal bus on the card as well.

The memory amount also means jack shit. The other ramdac simply steps in and reads during the next clock (166 or 200 million of them, btw 100hz refresh means only have to read 100 times a second out of those OR the dat out from the ram simply gets multicasted across the bus.

IT IS H/W accelerated, if zoomed/cloned. The g400 core writes to ram, the ramdacs both read from the same ram. IF it was a seperate screen (2 desktops in winblows...wow like winbloze needs real hardware for 2D *laugh*, OR a made-for-dualhead game) then perhaps it would actually have to share.

So far no one has brought about ANY good reason that framerate should drop measurably at all. So far I can only acount for maybe 100 more clocks per second needed. BTW ramdacs are at 300 or 360 mhz.

Drivers, perhaps? I'm all ears.