Date: Fri, 19 Sep 1997 18:08:13 +0930 From: Mike Smith <mike@smith.net.au> To: joerg_wunsch@uriah.heep.sax.de (Joerg Wunsch) Cc: hackers@FreeBSD.ORG Subject: Re: INB question Message-ID: <199709190838.SAA02899@word.smith.net.au> In-Reply-To: Your message of "Fri, 19 Sep 1997 08:49:37 %2B0200." <19970919084937.PR22228@uriah.heep.sax.de>
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> > > OBTW, see my trailing comment wrt. transfer rates; if ISA read cycles > > are deferred by 1.25us, how do I manage 1.3MW/sec from a user-space > > process? (This is with a P166 on an HX board; nothing special.) > > With a true plain ISA card? The boot code still uses an inb(0x84) for > a timing loop, and it seems to get the timing well enough with it. Yes, a "true plain ISA card". Specifically, a National Instruments AT-DIO32-F; the design is probably 5+ years old. > OTOH, 800000 transfers per second seem to support your figure. If the > transfers are 16 bits wide, this would be ~ 80 % of the theoretical > maximum. Read it again. 1.3MegaWords. Specifically, implying that it's making 1.3 million 16-bit I/O transactions per second, or 2.6MB/sec. Yes, this is substantially faster than I was expecting. 8) mike
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