sands@apple.com (Michael Sands) (05/09/91)
References:<1991May2.085707.11955@cascade.Stanford.EDU> <22883@natinst.natinst.com> Much of the information that Russell provides is correct. The 8*24 GC accelerates graphics and the user's experience in a couple of different ways. The host Macintosh is relieved of having to render the graphics. In many cases this is not a trivial amount of computation. I have seen an fx run twice as fast when the GC took responsibility for doing the graphics. This is highly dependent on the application and the mix of calculations and graphics and your experience may vary. The generic RISC processor used in the GC card is the AMD 29000. This is not a DSP or a series of custom ASIC's that are specific to the graphics task. This is a general purpose processor and is capable of accelerating most anything. In the case of the initial release of the Macintosh Display Card 8*24 GC, the code that is initially loaded on the card is the lower levels of the QuickDraw model, the current rendering model on the Macintosh. This code is capable of acclerating most of the rendering that is required. For example lines and scrolling and text are all accelerated. Some of this is easier and therefore goes faster. Lines are tough and scrolling is easy so lines are 7x faster and scrolling is 20-30x faster. The AMD 29000 is running at 30Mhz and provides roughly 19 MIPs (what ever those are) and 32,000 Dhrystones (them too?) It is the most powerful processor appearing in any Macintosh today. (Sorry, I get too excited sometimes.) The GC is capable of block transfers across the NuBus. Other third party graphics cards as well as the standard Macintosh Display Card are capable of receiving the transfers. If the GC card is in the machine along with a frame buffer card, the graphics on the frame buffer card will run faster because the GC renders everything. This is true even if the GC does not have a monitor plugged into it. Macintosh's with on board video will even be accelerated. In these cases the acceleration is not as great as of the GC were rendering to its own frame buffer because of the additional overhead of the NuBus. Hope this helps.... Michael Sands system extension group (408) 974-6108 novice driver, just my thoughts