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From: bgr@uncle-bens.rice.edu (Robert G. Rhode)
Newsgroups: comp.sys.atari.st
Subject: Re: Graphics on the STE - v. generally speaking...
Message-ID: <1991Apr16.211304.6829@rice.edu>
Date: 16 Apr 91 21:13:04 GMT
References: <1991Apr3.051045.1894@ns.network.com> <1991Apr03.150135.26529@chinet.chi.il.us> <40922@cup.portal.com> <1991Apr5.231704.19657@jato.jpl.nasa.gov> <1563@ipsi.UUCP> <1991Apr16.192259.4357@rice.edu>
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In article <1991Apr16.192259.4357@rice.edu>, bgr@uncle-bens.rice.edu (Robert G. Rhode) writes:
> In article <1563@ipsi.UUCP>, wallmann@ipsi.UUCP (Georg Wallmann) writes:
> 
> > always came up with "too expensive". Of course if you think 16 MB isn't
> > expensive ... as you do in your post. While thinking about it I
> > had this great idea for a new RAM technology, which unfortunately
> > (then unbeknownst to me) already existed as dual-port RAM. Even then the
> > bus width needed and the cycle speed is just about too ridicolous for
> > a home computer. Personally I'd be happy with 640*400*16bit colors at
> > 70Hz and some hires in mono. That would be monetarily feasible, I only
> > want color for the games <slobber> anyway, and some hires for programming.
> 
> I think I can (theoretically) offer you a better deal:
> 
> How about 1024x1024x24-bit color for <$350 parts cost (if you are an OEM)...
> 
> Ingredients:
> 24 1-Megabit Video Rams @ ~$12 each => 3 MB
> 1 Brooktree triple 8-bit RAMDAC @ ~@50
> glue logic
> 
> 1024x1024x70 Hz = 110 MHz pixel clock.
> Each VRAM is 256Kx4, so each VRAM needs to output at 27.5 MHz.
> A 100-ns VRAM is rated to shift out serial information at the rate of 33 MHz.
> 1 VRAM chip per bitplane.
> 
> A VRAM is a dual-ported RAM with a DRAM half and a serial shift register half.
> The two halves are completely independent of one another except when passing data
> between them.  512 bits (1 DRAM row) is transferred at a time.
> 
> Anyway, I am currently doing a theoretical video board design for a senior EE class,
> and I assure you that the performance you require is not at all unreasonable in cost.
> 
> - Bob
>  
Silly me, I forgot to tell it the right distribution.
By the way, that should say Brooktree VideoDAC, not RAMDAC.  A RAMDAC is what you use
when you want to have a 256-color lookup table for 8-bit graphics.  The Bt459
RAMDAC has a 256x24 lookup table for color information, 16x24 overlay color lookup table
for easy text-over-graphics or windowing applications, and even a 64x64x3-color cursor in
hardware (For those of you who want a sprite).

I hope this reaches more than just me this time...