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From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: net.micro
Subject: Re: Re: What is \"bitblt\" ?
Message-ID: <6275@utzoo.UUCP>
Date: Thu, 9-Jan-86 16:32:54 EST
Article-I.D.: utzoo.6275
Posted: Thu Jan  9 16:32:54 1986
Date-Received: Thu, 9-Jan-86 16:32:54 EST
References: <976@brl-tgr.ARPA>, <956@terak.UUCP> <6264@utzoo.UUCP>, <167@intelca.UUCP>
Organization: U of Toronto Zoology
Lines: 53

> > ... There's no reason why bitblt hardware can't use virtual memory the
> > same way the cpu hardware does, although it adds cost and complexity.
> 
> Well, if you are willing to make virtual memory hardware that responds
> in "real time..."  I'd think that would be more expensive than just having
> more memory!

You miss my point:  your cpu needs "real time" response too -- a few hundred
nanoseconds at the most, usually -- but it has no problem with page faults.
The process that was running simply gets suspended until the page is on hand.
There's no intrinsic reason why bitblt hardware couldn't do the same thing,
although it's not common.

> > Nonsense.  This is like saying that monochrome books are an endangered
> > species:  the color ones get all the hype, but monochrome still does most
> > of the work.
> 
> Oh come on!  Just because you haven't thought of any use for something
> doesn't mean it is useless.  I have used a color terminal for normal
> text editing, and have found it none the lacking.  In addition, the use
> of colors to highlight various things on the screen, whether they be
> text or graphics, adds another dimension to the display, one that is
> difficult to get with grey levels or hatch patterns...

I didn't say color was useless, just that it's significantly more expensive
and usually not worth the price.  To match monochrome clarity and resolution,
the price tag for the tube and the hardware to drive it is substantial.
Especially if you want high resolution, like say 1280x1024.  Color monitors
with that kind of resolution cost A LOT.

Highlighting is indeed useful, although much the same thing can be done with
high-resolution monochrome if you work at it.  As has been observed before,
color is often used as a substitute for detail.  I'd rather have the detail,
thanks -- it has so many other uses.

> With memory costs on the wane (or at least they were until the government
> got involved) I don't see the use of color displays going any way but up,
> even with the more expensive tube.

Memory costs are not the only problem; to update things at the same speed,
you also need several times the bitblt bandwidth.  And several times the
backing-store bandwidth.  Those are not as easy to come by as bigger memory.

I agree that color use is likely to increase.  Color in books is more common
than it used to be, too.  But most pages of most books are still monochrome,
for good sound economic reasons.

Given a choice between three monochrome systems, or a single color system
with slower display update, I know which I'd pick.  Last time I looked,
those two choices were about the same price.
-- 
				Henry Spencer @ U of Toronto Zoology
				{allegra,ihnp4,linus,decvax}!utzoo!henry