[comp.sys.apple2] Mac LC VRAM

curfmanm@prism.CS.ORST.EDU (Matthew Curfman) (02/08/91)

David Whitney writes:

| Ah, the 15-bit color claim is wrong. It's 16-bit. With the appropriate
| VRAM expansion. Which is high priced. That gives you 65536 colors on
| screen at once no tricks or stunts - not 4k. 

The Mac LC, when installed with the additional VRAM, does in fact have
only 15-bit color, with the remaining bit used as a misc. alpha channel. This
was confirmed by a call to an Apple Employee friend of mine here in Portland.

The educational discount here at OSU for the VRAM is $149.00, which I personaly
wouldn't consider that expensive.

15 bits will allow the LC to produce 32,768 colors at a time.  Why they didn't
use the 16th bit as a color bit, I don't know. What use is a one bit alpha
channel for anything other than some kind of overlay hardware? 
_______________________________________________________________________________
Matt Curfman                                                  Technovelty. Inc.
curfmanm@prism.cs.orst.edu                              Oregon State University
     OSU says what it says. I say what I say. We don't say the same thing.

torrie@cs.stanford.edu (The Ghost Who Walks) (02/08/91)

curfmanm@prism.CS.ORST.EDU (Matthew Curfman) writes:

>David Whitney writes:

>15 bits will allow the LC to produce 32,768 colors at a time.  Why they didn't
>use the 16th bit as a color bit, I don't know. What use is a one bit alpha
>channel for anything other than some kind of overlay hardware? 

  Apple's colour model is RGB, i.e. 3 components.  15/3 = 5 bits for each.
16/3 = 5.33333 bits for each.  My guess is that 32-bit QuickDraw (which is 
what model the 15-bit colour is using), assumes that each component is
the same size.

-- 
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Evan Torrie.  Stanford University, Class of 199?       torrie@cs.stanford.edu   
"If it weren't for your gumboots, where would you be?   You'd be in the
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