rod@venera.isi.edu (Rodney Doyle Van Meter III) (02/27/90)
I know our friends on the inside are named Agnus (Agnes? I've seen it spelled both ways), Gary, Denise, and Paula. I know Agnus has something to do with the difference between chip and fast RAM. Chip is the only memory that can be displayed on the screen, is that right? What exactly does Agnus do? Paula has something to do with controlling interrupts and devices? Who are Gary and Denise, sprites and voice synthesis? Besides the fatter Agnus, what does the Extended Chip Set provide? Will ECS run with a system clock of 25-33 MHz? Where did the names come from? Has Commodore given any thought to an asynchronous system? What tremendously hairy bag of ugly worms (to mix a metaphor) does this open up? --Rod
daveh@cbmvax.commodore.com (Dave Haynie) (02/27/90)
In article <12036@venera.isi.edu> rod@venera.isi.edu (Rodney Doyle Van Meter III) writes: >I know Agnus has something to do with the difference between chip and >fast RAM. Chip is the only memory that can be displayed on the screen, >is that right? What exactly does Agnus do? Agnus in her current form is a memory controller and address generator for everything that happens on the Chip bus. She contains the blitter and copper logic as well, and also creates all the video and chip clocks. >Paula has something to do with controlling interrupts and devices? Paula contains the logic for analog joysticks, the floppy disk data separator, all four sound channels, and the interrupt mixer/control. >Who are Gary and Denise, sprites and voice synthesis? Denise does the actual video display, based on addresses generated by Agnus. She contains the color registers, CLUT with HAM weirdness, etc. Gary is a gate array that provides chip selects to everything on the motherboard, some address decoding assistance to Agnus, Chip bus buffer control, some floppy disk decoding functions, and anything else that seemed appropriate to stuff in there. >Besides the fatter Agnus, what does the Extended Chip Set provide? Some extended video modes based around 35ns pixels. >Will ECS run with a system clock of 25-33 MHz? ECS runs from a nominally 28MHz clock, which gets divided down in various ways to provide pixel clocks and the nominally 7MHz clock which feeds the processor in a standard 68000 based Amiga. >Has Commodore given any thought to an asynchronous system? Asynchronous is what way? The A2500/30 is an example of a system from Commodore that uses a processor clock (at 25MHz) that's completely unrelated to the Chip subsystem clocks. I've always called this an asynchronous system. >What tremendously hairy bag of ugly worms (to mix a metaphor) does this >open up? The chance for metastability. Much care must be taken to avoid this in such a design. > --Rod -- Dave Haynie Commodore-Amiga (Systems Engineering) "The Crew That Never Rests" {uunet|pyramid|rutgers}!cbmvax!daveh PLINK: hazy BIX: hazy Too much of everything is just enough