simoni@strat.Stanford.EDU (Richard Simoni) (05/02/91)
How do graphics accelerators for the Mac (say for instance the Apple card with an AMD 29000) gain their graphics speedup over a stock Macintosh? That is, do they use: 1. Parallelism: Graphics operations are off-loaded to separate processor, allowing main processor to continue with other tasks. (In the Mac world, would this mess up the serialization of operations intended by the programmer?) For entirely graphics-bound operations, this parallelism obviously won't buy much. 2. Faster Graphics Processor: Graphics operations are off-loaded to separate processor which is faster than main processor. Main processor waits for graphics CPU to complete before proceeding. 3. Other factors: e.g., block transfers on bus to increase available bandwidth to memory, etc. Thanks to anyone who can help enlighten me on this topic. Apologies for rehashing what I'm sure others have asked before. Rich Simoni simoni@strat.stanford.edu
nkb@cunixa.cc.columbia.edu (Norman K Bucknor) (05/03/91)
In article <1991May2.085707.11955@cascade.Stanford.EDU> simoni@strat.stanford.edu writes: > >How do graphics accelerators for the Mac (say for instance the Apple card >with an AMD 29000) gain their graphics speedup over a stock Macintosh? That >is, do they use: > >1. Parallelism: Graphics operations are off-loaded to separate processor,.. >2. Faster Graphics Processor: Graphics operations are off-loaded to... >3. Other factors: e.g., block transfers on bus to increase available... >Rich Simoni >simoni@strat.stanford.edu I'm no expert, but from what I've read most accelerators do one or more of the things you've mentioned. Some Quickdraw operations do not benefit from this acceleration, so the effectiveness of the accelerator varies with what you're doing. Norman
davoli@natinst.com (Russell Davoli) (05/07/91)
In article <1991May2.085707.11955@cascade.Stanford.EDU>, simoni@strat.Stanford.EDU (Richard Simoni) writes: > > How do graphics accelerators for the Mac (say for instance the Apple card > with an AMD 29000) gain their graphics speedup over a stock Macintosh? That > is, do they use: > > 1. Parallelism: Graphics operations are off-loaded to separate processor, > allowing main processor to continue with other tasks. (In the Mac world, > would this mess up the serialization of operations intended by the > programmer?) For entirely graphics-bound operations, this parallelism > obviously won't buy much. The 8-24 GC does this. It apparently queues up a number of operations then performs them when it decides it has queued enough. When an operation is queued, the program gets control back to continue processing while the operation is performed. > > 2. Faster Graphics Processor: Graphics operations are off-loaded to > separate processor which is faster than main processor. Main processor > waits for graphics CPU to complete before proceeding. > The graphics processor on the 8-24GC is a RISC chip (an AM29000 I think). It's probably a lot faster at most operations than a 68000 series processor, but 1. is the way to go. > 3. Other factors: e.g., block transfers on bus to increase available > bandwidth to memory, etc. > The 8-24GC is supposed to be able to perform block transfers, but I don't know whether they are really used. The target memory must be capable of block mode access for this to work, so I'm guessing that most of the video cards out there don't have this hardware. Block transfers are a big plus since they take significantly fewer cycles than arbitrating on every transfer then performing the transfer. Hope this helped. Russell Davoli