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Date:      Wed, 17 Dec 1997 05:09:35 GMT
From:      jak@cetlink.net (John Kelly)
To:        Mike Smith <mike@smith.net.au>
Cc:        FreeBSD Hackers <hackers@FreeBSD.ORG>
Subject:   Re: 3com 3c509 card 
Message-ID:  <349a59c3.99678713@mail.cetlink.net>
In-Reply-To: <199712170334.OAA01300@word.smith.net.au>
References:  <199712170334.OAA01300@word.smith.net.au>

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On Wed, 17 Dec 1997 14:04:26 +1030, Mike Smith <mike@smith.net.au>
wrote:

>"AT Bus Design" (Edward Solari, Annabooks)

BTW, I checked on getting that book and it seems to be no longer
available.

>Now, if you take into account just a little CPU overhead, interrupt 
>cycle overhead, metadata overhead, you will quickly see that you're 
>not going to route 4MB/sec aggregate traffic through anything on the ISA
>bus, period.

I seem to have one 486 board running at 12 MHz ISA and clock doubled
50/100MHz DX4-100 CPU will no apparent problems.  This has reduced my
(measured) 8 bit I/O cycle time to 0.65 usec.  I don't have a suitable
method for measuring the 16-bit cycle time, but I'm hoping for nearly
4MB through this supercharged bus in 16-bit mode.  I'm only getting
about 700K per card, so I don't think I need a full 4MB anyway.  I
might even be able to use five interfaces -- they won't be saturated
all the time.

>Personally, I'd recommend a 4-port Zynx card.

I have a small truckload of SMC Ultras I need to use.

John





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