From:	DavMac AT iname DOT com (Dav)
Newsgroups:	comp.os.msdos.djgpp,comp.os.msdos.programmer,alt.msdos.programmer,alt.games.programming
Subject:	Re: Blit timing - complicated?
Date:	Mon, 01 Dec 1997 05:25:22 GMT
Organization:	Albury Local Internet
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To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

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 :)

I would say it's *possible*, but not with the usual hardware.

>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:
>- Access time of video RAM,
>- Whether real or protected mode is used,
>- other system characteristics?

I would imagine that actually timing it would be the best bet.  Do a few runs
through and take the average time.  Make sure you disable any disk cache
programs, multitaskers and EMM386 equivalents.  This will give you a *minimum*
time. (you might even want to disable interrupts during the blit)

Protected mode could slow things down if paging is enabled.  Otherwise, real and
protected mode timings should be almost exactly the same.

Dav.
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