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From: chucks@pnet51.orb.mn.org (Erik Funkenbusch)
Newsgroups: comp.sys.amiga.advocacy
Subject: Re: Blitter vs. 040 (was: Computer Architecture question
Message-ID: <4922@orbit.cts.com>
Date: 15 May 91 17:45:01 GMT
Sender: news@orbit.cts.com
Organization: People-Net [pnet51], Minneapolis, MN.
Lines: 40

elg@elgamy.RAIDERNET.COM (Eric Lee Green) writes:
>Just out of curiousity, where is a color card located in the NeXT? On a
>10mhz I/O expansion bus? That's the primary failing of most computers...
>they don't have a fast I/O bus. E.g. these "fast" '386 machines are most
>often cramming bytes into their super-hi-res VGA cards 16 bits at a time
>over a 8mhz (or 10mhz) bus... with bank switching, no less, to deal with
>the fact that you can't fit that much memory into a MS-DOS memory space.
>What a performance nightmare. From what I understand, the Mac folks have a
>similar problem with their NuBUS implementation... i.e., the processor
>can't jam bytes into the framebuffer at anywhere near the processor's top
>speed. For that matter, neither can the Amiga, in its current
>incarnations... but the A3000 still has twice the bandwidth into video
>memory, compared to the typical '386-based PC.

No, the 3000 has an Asynchronous bus, which means that the bus is as fast as
you want it to be.  and many 386's come with an EISA or Micro Channel bus that
is fully 32 bits and possibly asynchronous as well.  course these machines are
also MUCH more expensive than standard ISA buses.

>
>The blitter's functionality mostly applies to multitasking environments
>when you're talking 68040's. Even a 68040 isn't an unlimited resource. Note
>that there exists software patches for the A3000 to patch the OS's
>BlitBitMap etc. calls to use the CPU instead of the blitter... but most
>people still don't do it, because other processes slow down drastically
>when so much CPU is being used to shove bytes around on the screen. (Even
>though it DOES speed up the screen scrolling and such). n
>
>--
>Eric Lee Green   (318) 984-1820  P.O. Box 92191  Lafayette, LA 70509
>elg@elgamy.RAIDERNET.COM               uunet!mjbtn!raider!elgamy!elg

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