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- Path: sparky!uunet!mcsun!uknet!ieunet!tcdcs!maths.tcd.ie!ecarroll
- From: ecarroll@maths.tcd.ie (Eddy Carroll)
- Newsgroups: comp.sys.amiga.graphics
- Subject: Re: Problem with No New Copper in A4000
- Message-ID: <1992Sep15.105341.2778@maths.tcd.ie>
- Date: 15 Sep 92 10:53:41 GMT
- References: <1992Sep15.023838.16397@news.iastate.edu>
- Organization: Dept. of Maths, Trinity College, Dublin, Ireland.
- Lines: 24
-
- barrett@iastate.edu (Marc N Barrett) writes:
- >In the ECS, the copper requires 2 scanlines to update the palette registers
- >between pull-down screens. The AGA Lisa chip now has many more palette regs
- >but the copper has not been updates accordingly. The result is bigger
- >blank space between pull-down screens on the AGA chipset. A total of 11
- >scanlines of space, in fact. Thus, you can write off enhanced equivelents
- >to the Dynamic HiRes or SHAM modes for the AGA chipset.
-
- On the contrary, SHAM and Dynamic Hi-Res are much more feasible on the new
- chipset than on the old. If a screen uses less than 8 bitplanes, then a
- single register can be used to select the offset into the 256 colour table
- to determine which colours are actually used. (For example, a 6 bitplane
- hi-res screen can display colours 0-63, 64-127, 128-191 or 192-255). This
- allows the copper to reload one part of the palette at its own speed, without
- the screen being affected, and then load a single register to make all the
- changes take effect immediately, and saves having to play tricks with CPU
- timing.
-
- Granted, an enhanced copper with a block load facility would have been nice.
-
- Eddy
- --
- Eddy Carroll ----* Genuine MUD Wizard | "You haven't lived until you've
- Internet: ecarroll@maths.tcd.ie | died in MUD!" -- Richard Bartle
-