Date: Mon, 29 Sep 1997 03:44:52 -0500 From: Tony Overfield <tony@dell.com> To: Mike Smith <mike@smith.net.au> Cc: hackers@FreeBSD.ORG Subject: Re: INB question Message-ID: <3.0.2.32.19970929034452.006ff1c0@bugs.us.dell.com> In-Reply-To: <199709280920.SAA05505@word.smith.net.au> References: <Your message of "Sun, 28 Sep 1997 02:00:01 EST." <3.0.2.32.19970928020001.006ce080@bugs.us.dell.com>
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At 06:50 PM 9/28/97 +0930, Mike Smith wrote: >> 16-bit ISA I/O cycles are not only wider but also faster than 8-bit ISA >> I/O cycles. Back when IDE drives were still attached to the ISA bus, a >> fast drive could transfer about 3.5MB/sec, but 2.5MB/sec or 2MB/sec was >> more typical. The speed depends on the chipset and the way that the >> BIOS programs the ISA timing options. > >Gotcha. Hmm, does this mean that you can read an 8-bit peripheral >faster by using 16-bit cycles, No. >or will the sizing signals trip you up? Yes. Unless IOCS16# is asserted, the ISA controller will split the cycle into two slower 8-bit cycles. If IOCS16# is asserted, the cycle will be 16-bits wide and will complete faster.
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