Newsgroups:	comp.os.msdos.djgpp,comp.os.msdos.programmer,alt.msdos.programmer,alt.games.programming
From:	"William A. Barath" <wi534 AT vtn1>
Subject:	Re: High resolution timer problems..
In-Reply-To:	<65m5mt$ka9$1@news2.xs4all.nl>
Message-ID:	<Pine.GSO.3.95.iB1.0.971128035451.9846B-100000@vtn1>
Sender:	news AT freenet DOT victoria DOT bc DOT ca (News Manager)
Organization:	Victoria Freenet Association
References:	<65m5mt$ka9$1 AT news2 DOT xs4all DOT nl>
Mime-Version:	1.0
Date:	Fri, 28 Nov 1997 12:08:42 GMT
Lines:	30
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

On 28 Nov 1997 rkramer AT xs4all DOT nl wrote:

|In a discussion with a friend of mine, he was trying to convince me that
|it's possible to blit a full 800x600 screen in less than a millisecond. I
|tried to tell him otherwise, but couldn't quite get my point through :)
|
|Can anyone tell me how I could calculate the time it would take to blit a
|full VESA 0x103 screen, using a 486DX2 66 MHz? Is this an easy task, or a
|very difficult one? Do I have to keep in mind:

Well lesee here.  dx2/66 means a best bus speed of 33Mhz, with 32-bit
bandwidth, yielding a *possible* 132Mbyte/sec throughput, assuming zero
waitstates and zero hazards.  Now an 800x600 screen on a local bus
graphics adapter just might be zero waitstate, so lets continue giving
your friend the benefit of the doubt.  Lets also assume a 256-color screen
because otherwise we are guaranteed large bus waits for VGA memory.  So we
are going to blit 800*600 bytes, approx .5 meg, with 132Mbytes/sec of
bandwidth.  Assuming that load and store will take the same amount of
bandwidth, we can blit 66 megs through his bus per second.  Now to do it
in a millisecond, we need 1000 times .5meg times two, or a gig/second of
bandwidth.  But lets again be charitable and assume that he has hardware
that nobody else on the planet has, and give the point to him.

Not.


-Wil Barath  "I feel as though I see my pen to write"
  aka WseM    homepage: http://victoria.tc.ca/~wi534

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