----- Original Message ----- From: "Bruce Johnson" <[EMAIL PROTECTED]>
To: "G-List" <[email protected]>
Sent: Tuesday, January 25, 2005 12:30 AM
Subject: Re: AGP video cards sharing system memory
On Monday, January 24, 2005, at 05:13 PM, Joshua Coombs wrote:
Core in Tiger moves all the work to the GPU. This will result in the bus seeing lower utilization, (meaning PCI cards should be enabled if they have enough ram) but more ram use by the GUI.
Read the info:<http://www.apple.com/macosx/tiger/coreimage.html>
Tiger isn't moving 'all the work' to the GPU, more like they're using the GPU as a graphics co-processor, like a math co-processor for FP operations would be used. (or Velocity engine for vector operations).
Hrmm... that'd mean the bus IS going to be hit hard, so PCI cards will continue to be hurt under OS X, as it will be more of a streaming operation, much like now.
One thing you're missing here is that for screen purposes (and the things that CORE is set to do) 32 MB is quite a bit of ram.
1280x1024x24 (32bit color, as I don't believe any modern GPUs do packed data for framebuffer, I could be wrong though.)
1 framebuffer copy - 41943040bits
Standard is to double buffer - 83886080bits
Z buffer, 32bit (We're running 3d remember) - 41943040bits
Total before textures/scratch space - 125829120bits / 15MB
That leaves 17MB for textures/scratch as the 9200 doesn't support DIME and can't texture from system ram directly
Open Safari full screen, thats close to 4MB of texture by itself, Photoshop with a few images full screen, 4 to 10mb easy. If Quartz/Core do tripple buffering, you loose annother 4mb off the top as well. 32MB isn't something to laugh at, but it's not as forgiving as 64MB or more either.
The reason that games require such massive amounts of Video ram is for storing texture and shape databases, plus do rendering of normals for bump maps, Z-fields for things like haze and mist effects.
Look at the list of effects (they call them 'Image Units'). They look like the Photoshop 'Filters' menu.
They're all straight, single transforms on pixel arrays, all 2-D, not 3-d stuff like higher end games stuff is doing.
These are processor, not memory intensive.
Big difference; you don't need huge RAM buffers for that work.
Also, the mini does have 4X AGP. While this isn't top end by any means, come on, it's not like it's nothing!
Agreed, but 1GB/s is still far slower than than the 6GB/s it has to local ram. (Based on PC specs saying it has a 128bit memory interface and clocks the bus at 400mhz. I couldn't find any 32mb cards to base that on, so it may run the memory interface at 64bit, or 3GB/s.)
The Mini may have enough raw GPU horsepower to tackle Core, but die because it's light on ram, and then be doubly hit by not allowing DIME mode which would have allowed it to attempt it rather than having to fall back hard on the CPU when it runs out of ram.
You gotta love it...the 9200 in the mini, so wretchedly 'low-end' you're already disimissing it as a failure, is about what a year or two out of being the TOP end of graphics?
The 9200 is two generations behind the curve in ATi's product line, not only that, it's a castrated version of their top tier product for that generation. It's pixel/vertex shader support is not floating point, or DX9 class if you want to use PC conventions. Based on the orriginal requirements for Core to use the GPU posted by Apple on their website, they were targeting cards with floating point pixel shaders, which would leave the 9200 out.
It may only be one or two years old from date of product naming, but the tech is decidely older and slower.
As for how Apple's going to handle it? They say on the Core web page:
"For computers without a programmable GPU, Core Image dynamically optimizes for the CPU, automatically tuning for Velocity Engine and multiple processors as appropriate."
Simple, anything it can offload to the GPU it does, what it can't it sends to the vector co-processor in the G4, using multiple processors as needed.
So in short, your answer is: The Mini will do Core stuff just fine. As well it should...I suspect the design engineers would be hanging from the yardarms in Cupertino if it doesn't run Tiger well.
This should make stuff like iMovie kick a**...real-time transitions anyone?
(a DV frame is tiny in comparison to the screen...32 MB is more than enough to hold a bunch of frames.)
I dunno, all evidence says Core will not be running on the GPU on the mini, leaving the Velocity Engine to pick up all the slack. Time spent in the velocity engine is time you're not running user tasks. This is all wild speculation at this point, but I do question the mini's capibilities as a hardCORE system.
Granted, it's a $500 throwaway system, its not MEANT to be teh ubar box for high end work... : )
Mini's are out, so it'll be interesting to see the reviews hit for them. As for how long we have to wait for tiger... no idea.
Joshua Coombs
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