pix,

Some of this is just educated guess, so take what you want.

Is this increased frame rate in games/ movie playback, smoother scrolling, and support for higher resolutions?

Yes, no, maybe, and yes. Games yes, if your previous card didn't have enough memory to keep the textures you need in memory. If it did, memory and graphic chip speed will make more difference. For example the 64meg Geforce4 4200 is typically a few frames faster in most games than the 128meg because the memory is clocked faster on the 64meg. However, some of the newer games that use lots of large textures that will reverse. The 64meg doesn't have enough space so spends more time getting the textures from main memory.

As far as I know memory will not impact video playback.

Scrolling, probably not, but maybe if the driver was doing stuff like caching bitmaps in video memory.

And finally certainly yes for higher resolutions, but that probably won't make much impact anymore. 1600x1200x32 takes less than 8meg for a frame buffer. You have to look pretty hard to find a video card that has less than 32meg these days.

I've also heard that Jaguar was going to offload all of the operating system graphics to the video card. so in that sense, a better video card would mean a smoother moving UI, right?

Yes, from what I understand Jaquar will generate textures of windows and use the video cards 3D engine for the transparency effects and so forth. Theoretically more video memory would mean more textures (windows) could be kept in video memory so the UI would be snappier. My only Mac has a Geforce2 MX with 64meg I think so I can't really say "oh, 64meg peformance is way better than 32meg". I have nothing to compare it to.

Lastly, what about cards with the dual monitor support. Say you've got 2 displays running off an ATI 9000 with 64MB of RAM. Basically that's 32 per display.

Probably not, I would image that the card would allocate whatever each display needed so if one monitor is 1600x1200x32 it gets about 8meg and the other at 640x480x8 gets about 300k. The rest is used for texture memory, double buffering, etc. This is pure speculation though.

would there be an advantage to buying a PCI graphics board for one of the displays so that you could have the AGP and full 64megs dedicated to your main monitor?

These days, at least on the PC side, you can get a wicked fast video card that will drive two monitors for about $100. On the Mac side it's a little more expensive, but still reasonable. I can't imagine that having an extra PCI card would do much for you except suck up a precious PCI slot and most of the time vendors won't release PCI versions of their fastest card so you end up putting a lowerend card in the PCI slot. Again, pure speculation, but that might be an interesting experiment. Personally, if I was building a machine from scratch I'd go for a single AGP card. I do use a dual monitor machine in the day job and there I have two video cards, mostly because I had the PCI video card laying around collecting dust so why not save myself a few bucks and use it.

Best regards,
Eric Winemiller
Digital Carvers Guild
Freeware and commercial 3D extensions
http://digitalcarversguild.com

Eric Winemiller
Digital Carvers Guild
Carrara and LightWave plug-ins