Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uunet!bu.edu!polygen!jerry
From: jerry@polygen.uucp (Jerry Shekhel)
Newsgroups: comp.sys.amiga.advocacy
Subject: Re: (Video) Hardware Idiots ?
Message-ID: <1143@stewart.UUCP>
Date: 18 Jun 91 13:58:26 GMT
References: <1991Jun9.151244.8883@cunixf.cc.columbia.edu> <1991Jun9.184849.4299@neon.Stanford.EDU> <1991Jun10.043321.21692@cunixf.cc.columbia.edu> <375@orac.UUCP>
Reply-To: jerry@stewart.UUCP (Jerry Shekhel)
Organization: Polygen Corporation, Waltham, MA
Lines: 31

In article <375@orac.UUCP> bret@orac.UUCP (Bret Indrelee) writes:
>
>VGA lives on the ATbus (now sometimes called the ISA bus).  This bus
>is slow.  It is difficult to get any kind of random access runnings at
>greater than about 2Mbytes/sec (possible, just difficult) assuming the
>CLK is running 8 1/3 MHz.  Run it any faster and you better be ready
>for an unreliable system, or invent a logic family that can work in
>about -5nSec ;-)
>
>The time of signal propagation doesn't allow enough time for a board
>to assert *READY to insert wait states if you run your ATbus at greater
>than 8 1/3 MHz, and not every piece of hardware can run zero-wait states.
>At 10 MHz, you have to be able to respond before the signals have settled
>(thus requiring negative time) to meet the ATbus spec.
>

I don't know about this.  I just recently switched my 33MHz 386 to an ISA
bus speed of 11MHz, and I have yet to see a problem.  Granted, I only have
3 boards -- a disk controller that's been tested with bus speeds of up to
16MHz, the SuperVGA, and a parallel/serial/game card.  But if cards are
advertised as having been tested in high-speed ISA buses, I seriously doubt
your "negative time" requirement.
--
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| JERRY J. SHEKHEL  | POLYGEN CORPORATION  | When I was young, I had to walk |
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|                            jerry@polygen.com                               |
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