[johnzoidberg]

I have a 12-inch, 1GHz PowerBook G4 with a 32MB video chip inside. I know I can drive the new 20-inch Al Cinema Display in dual monitor mode, but can I do it well? Will video and GUI performance on both the 12-inch built-in display and 20-inch Cinema Display connected to it be decent, on par with the performance I'm seeing right now on a single 12-inch display alone? Is 32MB too underpowered to drive both displays in dual display mode that I will see hiccups or pauses when I do CPU/GPU intensive work?

[sworthy]

Unfortunately I can't answer your question directly,but my experience with external displays and my 12" is that you probably won't use both at the same time. My pb's screen is just too dim and creates a weird mix when you have a nice bright lcd next to it. I'm interested to hear about the graphics card though now that people are getting them.

[videian28]

I use the exact same setup, seems to work ok, expose is a bit choppy at times, but not enough to bother me

[CatOne]

Originally posted by johnzoidberg:
I have a 12-inch, 1GHz PowerBook G4 with a 32MB video chip inside. I know I can drive the new 20-inch Al Cinema Display in dual monitor mode, but can I do it well? Will video and GUI performance on both the 12-inch built-in display and 20-inch Cinema Display connected to it be decent, on par with the performance I'm seeing right now on a single 12-inch display alone? Is 32MB too underpowered to drive both displays in dual display mode that I will see hiccups or pauses when I do CPU/GPU intensive work?

32 MB is PLENTY to drive both displays. Performance (ESPECIALLY in 2D) isn't really affected by the amount of RAM on the card, it's more dependent on the chipset.

For example, a Radeon 7500 chipset with 128 MB of RAM will be significantly slower than a Radeon 9000 chipset with 16 MB of RAM. The only exception would be if you were paying 3D games, where the texture sets couldn't fit completely in memory.

The hiccoughs/pauses are note related to the amount of RAM.

[tooki]

The only place you're likely to notice anything is when using Exposé with lots of windows open. Exposé (and Quartz Extreme in general) is VRAM-sensitive, but because AGP is efficient, it's rarely a problem.

tooki

[kafoochy]

Originally posted by CatOne:
32 MB is PLENTY to drive both displays. Performance (ESPECIALLY in 2D) isn't really affected by the amount of RAM on the card, it's more dependent on the chipset.

For example, a Radeon 7500 chipset with 128 MB of RAM will be significantly slower than a Radeon 9000 chipset with 16 MB of RAM. The only exception would be if you were paying 3D games, where the texture sets couldn't fit completely in memory.

The hiccoughs/pauses are note related to the amount of RAM.

I was going to say the same thing. The chipset has a limit to the resolution, but with normal [2D] work, performance isn't going to be affected even close to the max resolution. The GPU doesn't really have to do much with 2D work; it's putting the picture on the screen that the CPU gives to it. With Expose (Quartz Extreme to a small amount), any 3D work, and certainly with Tiger 10.4, the GPU has to do much of the processing work and your computer would probably be fairly taxed. I don't think that is anything you need to worry about too much. If you had a CRT, you might have to worry about what refresh rates were supported, but you're talking about an LCD and don't need to worry about that! I say get the 20" You'll be very happy with it, and it will be a good investment if you want to get a new laptop some day.

[tooki]

OK, so here's the thing: in Mac OS X, the contents of every single window are stored in RAM as a 32-bit bitmap image, and in Quartz Extreme, each one of those bitmaps is used as a texture on a polygon. The more of the window textures that can be fit into VRAM, the better. AGP allows efficient access to system RAM as extra VRAM, but the real VRAM is better. On my system right now, with a few Safari windows open, and a bunch of windows in Eudora, the windows are consuming hundreds of MB of RAM.

tooki

[nJm]

I don't know if this is my imagination or not, but I am sure when I'm running my iBook G4 with the Screen Spanning hack that expose seems slower. I run a 17" CRT at 1280x960. I find dropping it down to 1024x768 (the same res as the iBook's LCD) it doesn't seem choppy? I believe when having an extended desktop my VRAM is split in two between the screens (so 16mb each). I do not know if the same thing happens when using the default 'mirror' option.

Could I use a 20" on my iBook? I know you can get little adaptor plugs to turn a DVI port into VGA. Does the reverse exist? Even if it does, would the display work running off an analogue VGA output?

[sworthy]

yes, there are vga -> dvi adaptors available. If my memory serves they're very expensive, as in over $200 at least. It would probably work, but the performance may not be as good (depending on which ibook you have) and it would be very expensive.

[tooki]

Originally posted by nJm:
I don't know if this is my imagination or not, but I am sure when I'm running my iBook G4 with the Screen Spanning hack that expose seems slower.

It's not your imagination. I can reproduce the same reduction in Exposé speed on my 1.25GHz PowerBook (which has a 64MB graphics chip).

tooki

[wuzup101]

Originally posted by sworthy:
yes, there are vga -> dvi adaptors available. If my memory serves they're very expensive, as in over $200 at least. It would probably work, but the performance may not be as good (depending on which ibook you have) and it would be very expensive.

I'm fairly certain the VGA > DVI adapter isn't nearly that expensive. Most higher end video cards in the PC realm come with them. Unless there is something special about Mac video cards (which I don't think is the case) I wouldn't see why you couldn't use one of these.

Some quick searching at newegg.com turned up this costly sub $4 adapter which is what I am talking about Here

[tooki]

No, it's the DVI->VGA adapters that are cheap. They're a simple plug adapter, because DVI-I includes all the VGA signals, so the adapter just has to take those wires and conect them to the right pins on the VGA plug. Apple includes these adapters, too.

VGA->DVI adapters are costly, because they are a box that takes the VGA signal, digitizes it, and then outputs it as DVI-D. It's an active device, not a passive one like the one above.

Note that generally speaking, when describing adapters, one talks about "Plug A -> Plug B", where Plug A is the connection on the computer, and Plug B is the desired output that the computer lacks. Newegg's product is a weird one. I'm guessing it's for one of two things: for when you have a VGA graphics card, and a DVI-I monitor (that is, DVI and analog), and you want to connect the DVI-I monitor to it using analog, but with a DVI cable, OR when you have a VGA monitor and a DVI-I graphics card, and want to connect them using a DVI cable, in which case their adapter would go on the monitor end. Either way seems "forced" to me.

tooki

[MrForgetable]

say I use my Powerbook with a 15 inch LCD running at 1024x768, that wouldn't be too bad with 64MB Video Ram would it?

[wuzup101]

Tooki sorry about that, thanks for point out that problem. I didn't notice that the product said (not for DVI-D which I'm assuming the 20" is...). My mistake!