In a message dated 2005-01-24 9;04;22Mrng, [EMAIL PROTECTED] writes:
<< Second, why is it so vital to upgrade the video memory on the Mac Mini? This technique does NOT work well for games...which is pretty much the only reason these days for needing lots of VRAM. >>
I guess i didnt know the performace would be that bad. My thought was, if it
has direct access to the system memory, which in some cases is faster than
the memory on video cards, it should be about as fast. Then again, I didnt put
2 and 2 together...Ive seen PeeCees with integrated graphics...really slow.
The AGP spec includes DIME mode, which I believe stands for DIrect Memory Execution. The AGP card is allowed to directly address system ram to use as additional texture space. The goal was to lower the cost on video cards by reducing the amount of expensive ram used on the card with cheaper ram on the PC. In reality, the slow speed of AGP in the 1x and 2x days, combined with OpenGL and DirectX drivers that didn't know how to deal with DIME well, resulted in it's use disapearing. Most modern graphics chipsets are incapible of doing AGP texturing. Gaming and professional users have driven the market for higher end video cards, so the theory is why waste driver development and transistors on something noone will use?
With PCIe, the idea is being explored again. Witness the Nvidia GeForce 6200 TurboCache product. This is a video card that ships with a paltry amount of ram, and is designed explicitly to do texturing over the PCI express bus. It does so quite well.
http://www.anandtech.com/video/showdoc.aspx?i=2300
It doesn't blow the doors off current top end hardware, but it will do things like smack 5200's around. It'll come knocking on the doors of the ATi 9200, ala the Mac Mini, and rain on it's parade as well.
Now, as far as 'intergrated graphics' on 'peecee's. Be careful what you turn your nose up at. While there are quite a few systems sporting Intel GMA video, that is infact, an intergrated to the chipset setup, there are other examples that show the breed is not all bad. Both Nvidia and ATi have chipsets with intergrated graphics based on their current GPU designs, that deliver damn good performance. They also have AGP slots ready to accept upgrades if the existing setup isn't good enough.
Remember the bit above about DIME not being used, that leads to annother interesting point. There are PCI versions of last gen hardware, Nvidia 5700s, etc, and they don't perform very differently than their AGP breathern because they DON'T do DIME. Quartz Extreme on the other hand, was purposely disabled on PCI video cards because it does a form of poor man's DIME. The CPU does all base window rendering, and then shoots that info up to the GPU as textures for it to compost. Good speedup in the UI, but a massive bus hog at the same time. 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. 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. Should be interesting to see how Apple handles this.
Joshua Coombs
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