DSEAH@WPI.BITNET (12/09/88)
Would is be correct to say that the reason that the Apple IIGS has to slow down is because of the Mega II? I was going through the Hardware reference and was reintroduced to the concept of shadowing, FAST RAM and sloooow RAM. Many books say that the GS must slow down to write to screen memory to 'maintain compatibility' with the Apple II. How fast is the Mega II capable of running? I don't have the Hardware Ref with me right now, but let me postulate this: The Mega II controls, among other things, video updates. The Mega II, as a II-in-a-box, is so complicated that it just barely creeps along at 1MHz. Could this be the reason? How does shadowing physically work? Does one write to one of the fast RAM banks, and shadowing DMA's it into slow RAM? Does the MegaII grab the address, data, and control buses sometime to steal some cycles from the 65816?