Newsgroups: comp.sys.apple2 Path: news.weeg.uiowa.edu!news.uiowa.edu!uunet!paladin.american.edu!europa.asd.contel.com!darwin.sura.net!spool.mu.edu!yale.edu!yale!gumby!destroyer!cs.ubc.ca!alberta!kakwa.ucs.ualberta.ca!ee.ualberta.ca!jpenne From: jpenne@ee.ualberta.ca (Jerry Penner) Subject: Re: Double low/hi Res Message-ID: Sender: news@kakwa.ucs.ualberta.ca Nntp-Posting-Host: eigen.ee.ualberta.ca Organization: University Of Alberta, Edmonton Canada References: <1992Nov9.235907.3531@mnemosyne.cs.du.edu> Date: Thu, 12 Nov 1992 05:05:15 GMT Lines: 51 sledbett@nyx.cs.du.edu (Shawn Ledbetter) writes: >I've read somewhere about the Apple ][e/][c/][gs that it can handle >double lo-res/hi-res. Does anyone know the poke values or any other >information I need. Thanks in advance. double lo-res: $C05E (49246) ; double-res $C056 (49238) ; lo-res $C052 (49234) ; full-screen $C050 (49232) ; graphics on double hi-res: $C05E (49246) ; double-res $C057 (49239) ; hi-res $C052 (49234) ; full-screen $C050 (49232) ; graphics on Now, depending on whether you have the 80-column firmware enabled or not, you may need to hit some more soft switches. If you are going to do all the work yourself (ideally in assembly language for speed), and you are starting with the machine in 40-column mode with the 80-column firmware disabled, then do this: sta $c001 ; poke 49153,0 ; ; turns on 80STORE switch sta $c00d ; poke 49165,0 ; turns on 80 column video mode If the 80-column firmware is already on and you're in 80-column mode, you don't need to do this since the firmware already did it. Keep in mind that if you do this yourself you will confuse the firmware if you try to print or input characters through it. To access the graphics (either double-lo or double-hi), the pixels are accessed starting in the AUX memory bank (bank 1 on IIgs) and then in the MAIN bank (bank 0 on IIgs). They alternate for every double-lores pixel and every seven double-hires pixels. To access the AUX memory, you hit $C055 (49237) (PAGE2) and then read or write the location. To access the MAIN memory, hit $C054 (49236) (PAGE1) and read/write. If you can get a IIe Technical Reference Manual, a IIc Tech Ref, or a IIgs Hardware ref, it will clearly show how video display memory is laid out, and will clarify all the details here. The best way to learn is to experiment on your own. Disassembling the video firmware always helps as well. Disassembling the lo-res graphics routines (start at $F800 in the monitor ROM) and the Applesoft hi-res routines ($F3xx to $F7xx) will also tell you a lot. Have fun. -- Jerry Penner jpenne@ee.ualberta.ca Try a 1-line .sig today.