Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!sun-barr!newstop!sun!coherent!next!aozer
From: aozer@next.com (Ali Ozer)
Newsgroups: comp.sys.next
Subject: Re: Something fishy with the Color Slab
Keywords: VRAM COLOR FISH
Message-ID: <298@next.com>
Date: 20 Nov 90 21:40:25 GMT
References: <10326@uhccux.uhcc.Hawaii.Edu>
Reply-To: Ali_Ozer@NeXT.com (Ali Ozer)
Organization: NeXT, Inc.
Lines: 23

In article <10326@uhccux.uhcc.Hawaii.Edu> The Obscure Guru writes:
>	Has anyone noticed something funny with the specs for the
>NeXTStation Color?  My copy of the progaganda says that the machine
>has 1.5 Megabytes of VRAM for the display.  However, this does not appear
>to be enough considering the following specs on the display itself:
>	16 bits per pixel
>	1120 pixel horizontal res
>	832  pixel vertical res
>Thus, 2(bytes) * 1120 * 832 = 1820 Kbytes ~= 1.777 Mbytes

The VRAM used for the screen does not need to store the alpha. The backing
stores of windows *are* 16 bits. However, when a window is displayed
on the screen, there's no need to show the alpha bits; transparency is
used when you composite between windows, and then you end up using the backing
stores.

The same holds for the 2-bit display and the NextDimension; the screen VRAM
doesn't keep alpha.

BTW, the screen VRAM is separate from the memory in the machine, so you have
that 1.5M in addition to the 12M in the NextStation Color.

Ali