VDC "Extended Background Color Mode"?
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From: Vanessa Ezekowitz on 2 Oct 2009 22:51 On Fri, 2 Oct 2009 06:13:18 -0700 (PDT) saehn <shanefell(a)gmail.com> wrote: > Sorry, I see now that I may have been a bit unclear. The "text" part > of EBGM was only to achieve a blocky 80x50 pixel mode, with each cell > being capable of two colors. So, in 640x200 mode, each 8x8 color cell > would contain two "software" pixels, each being comprised of 8x4 real > pixels. Does that make more sense? What Vanessa is describing seems > like it might work. Yeah, that would work - better would be to use 8x4 cells instead, then each "pixel" gets its own byte of attribute memory (as long as you don't further sub-divide the cells as previously mentioned). -- "There are some things in life worth obsessing over. Most things aren't, and when you learn that, life improves." http://starbase.globalpc.net/~vanessa/ Vanessa E. <vanDEesLEsaTEezTHekISowitz(a)gmail.com> (Delete the obvious to email me)
From: lyricalnanoha on 3 Oct 2009 08:11 On Sat, 3 Oct 2009, Errol Smith wrote: > adric22 wrote: >> I also created a program that put the VDC into a mode where the color >> cells were 8x2 in size. Then I filled the left 4 pixels of each cell >> and created a 160x100 graphics mode that allowed any of the 16 colors >> to be used and placed next to each other. I had theorized that it >> might even be possible to create a 160x200 graphics mode with some >> tweaking which would allow importing of C64's multi-color bitmaps >> (such as koala) but I never got that far. > > I've heard of this, a similar mode was used on IBM CGA adapters as well to > make a 160x100 16 colour mode. (Actually, the VDC and CGA have a lot in > common, the modes are produced in an identical fashion). > > 160x200 is theoretically possible but would require some timing tricks. A > mode like this is used in the RFO VDC demo to display an FLI like image, > although it is not full screen height. > > Errol > Am I not right in saying the VDC is a descendent of the 6545 used in the PET? And that's a clone of the 6845 used in the CGA. So it's not even a coincidence - they're actually fairly closely related. -uso.
From: Rick Balkins on 25 Oct 2009 00:48
Loosely, yes. It is technically a CGA/Digital RGB type video chip but I doubt the VDC is an actual "CGA clone" "lyricalnanoha" <lyricalnanoha(a)usotsuki.hoshinet.org> wrote in message news:4ac73f81$0$6556$c5fe31e7(a)read01.usenet4all.se... > > > On Sat, 3 Oct 2009, Errol Smith wrote: > >> adric22 wrote: >>> I also created a program that put the VDC into a mode where the color >>> cells were 8x2 in size. Then I filled the left 4 pixels of each cell >>> and created a 160x100 graphics mode that allowed any of the 16 colors >>> to be used and placed next to each other. I had theorized that it >>> might even be possible to create a 160x200 graphics mode with some >>> tweaking which would allow importing of C64's multi-color bitmaps >>> (such as koala) but I never got that far. >> >> I've heard of this, a similar mode was used on IBM CGA adapters as well >> to make a 160x100 16 colour mode. (Actually, the VDC and CGA have a lot >> in common, the modes are produced in an identical fashion). >> >> 160x200 is theoretically possible but would require some timing tricks. A >> mode like this is used in the RFO VDC demo to display an FLI like image, >> although it is not full screen height. >> >> Errol >> > > Am I not right in saying the VDC is a descendent of the 6545 used in the > PET? And that's a clone of the 6845 used in the CGA. So it's not even a > coincidence - they're actually fairly closely related. > > -uso. |