Why does my system lag so bad when I use two monitors?

[sofakng]

I have one computer (Core 2 Duo E6600 @ 2.4 GHz, 2 GB RAM, 8800 GTX) and two monitors (24" 1920x1200 and 20", 1680x1050).

When I start two instances of the game and keep both windows on the same monitor they both run smooth as butter and my processor(s) usage is at around 35% but when I move one window to another monitor it jumps to 65% and both games start lagging.

I've tried forcing the CPU affinity so each process has it's own CPU but it didn't help.

What am I doing wrong here?

EDIT: I'm using Octopus as my KM multiplexer, but I'm not even talking about using that yet. I'm just starting two instances of World of Warcraft manually...

[BobGnarly]

Windows XP?

It doesn't handle D3D apps across multiple monitors well at all. Vista is much better.

If you don't care about the non-native res on your 24", you can set it to horizontal span which will help a lot. I, personally, couldn't stand it.

[Nitro]

I found XP's Horizontal Span mode with one graphics card and two monitors to be far superior to Vistas Dual Monitor mode with 2 graphics cards and 2 monitors.

[Ozbert]

Windows XP?
It doesn't handle D3D apps across multiple monitors well at all. Vista is much better.
If you don't care about the non-native res on your 24", you can set it to horizontal span which will help a lot. I, personally, couldn't stand it.

This.

You could try Span but as BobGnarly says, you'd have to drop your 24" monitor down to 1680x1050. I also tried Span on a very similar specced PC to yours and it was still pretty crap.

Then I switched to Vista 64 and everything is now fine running five WoW instances on two 1920x1200 screens.

[sofakng]

Yeah, I'm using Windows XP. I actually own Windows Vista (Home Premium) but don't have it installed but maybe I'll install it on another partition or something and dual-boot.

I need to use the native resolution on my 24" so I don't think horizontal span will work for me.

Will Vista (32-bit) run the two instances of WoW (on different monitors) at the same speed as running them on one monitor?

I'm assuming my RAM, CPU, and GPU aren't the problem because if I just use one monitor both instances run lightning fast...

[Fuzzyboy]

I found XP's Horizontal Span mode with one graphics card and two monitors to be far superior to Vistas Dual Monitor mode with 2 graphics cards and 2 monitors.

Is there any way to avoid having system pop-ups appear in the middle of the setup so the dialogue boxes get cut in half? Because I find that highly annoying. Running vista atm and tbh I'm a bit tired of the poor performance.

[Nitro]

I found XP's Horizontal Span mode with one graphics card and two monitors to be far superior to Vistas Dual Monitor mode with 2 graphics cards and 2 monitors.

Is there any way to avoid having system pop-ups appear in the middle of the setup so the dialogue boxes get cut in half? Because I find that highly annoying. Running vista atm and tbh I'm a bit tired of the poor performance.

I've not tried it but my wife uses UltraMon and I believe I saw settings for soemthing like that.

[zanthor]

I've not tried it but my wife uses UltraMon and I believe I saw settings for soemthing like that.

Ultramon handles dialogs when using dual monitors in twinview not span. Unless they updated int he past 2 years since I looked last .

[sofakng]

How well does Vista 32-bit work for D3D apps on different monitors versus Vista 64-bit?

I'm a bit hesitant from installing 64-bit because I've been told there is very, very little difference (unless you have > 4GB RAM) and it could only potentially cause problems.

[phara]

AFAIK all pre-vista OS's have issues rendering to a second monitor in dual view. Vista is a little better but still not nearly good enough for me. The only thing I find acceptable is xp with horizontal span (you cannot do span in vista, evar).

With the same hardware, 2 instances of <any directx app> running under dual view monitors, I got max ~5fps in xp and ~20fps in vista on the second monitor.

Same hardware under xp with horizontal span - with FIVE instances running, I can get 60 fps on any window.

Is there any way to avoid having system pop-ups appear in the middle of the setup so the dialogue boxes get cut in half? Because I find that highly annoying. Running vista atm and tbh I'm a bit tired of the poor performance.

I searched high and low for registry settings to change this is xp span mode. I didn't find anything.