Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!husc6!rutgers!rochester!pt.cs.cmu.edu!andrew.cmu.edu!mp1u+ From: mp1u+@andrew.cmu.edu (Michael Portuesi) Newsgroups: comp.sys.amiga Subject: EGA/VGA (was Re: Silver (was Re: Amiga 2000 has been swapped)) Message-ID:Date: 18 Sep 88 21:55:33 GMT References: <2@orbit.UUCP> <6908@well.UUCP>, <786@applix.UUCP> Organization: Carnegie Mellon Lines: 20 In-Reply-To: <786@applix.UUCP> > *Excerpts from ext.nn.comp.sys.amiga: 25-Aug-88 Re: Silver (was Re: Amiga* > *2.. Scott Evernden@applix.UU (1883)* > Anyways, the killer with EGAs/VGAs, is that you _have_ to get down and dirty > with the IO registers to accomplish any real work. This is quite a painful > process on the non-memory-mapped-IO 80x8x's. You repeatedly play games like: > mov dx,SEQ_ADDR; mov al,WPL_REG; out dx,al; inc dx; mov al,1; out dx,al). > Registers are pretty much lost, like DX, for this- on an architecture that is > already register-starved. The way the problem with VGA was explained to me, it is possible to memory map the *first* bitplane of display. Accessing any further bitplanes require the bogus gymnastics detailed above. --M Michael Portuesi / Information Technology Center / Carnegie Mellon University ARPA/UUCP: mp1u+@andrew.cmu.edu BITNET: rainwalker@drycas "if you ain't ill it'll fix your car"