Date: Sun, 25 Feb 1996 01:03:35 +1100 From: Bruce Evans <bde@zeta.org.au> To: bde@zeta.org.au, msmith@atrad.adelaide.edu.au Cc: hackers@FreeBSD.org, petzi@zit.th-darmstadt.de Subject: Re: 230.400 bps on serial port Message-ID: <199602241403.BAA06181@godzilla.zeta.org.au>
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>> - IDE disks have no effect on serial communications under FreeBSD. >> (Bus-hogging DMA controllers may have an adverse affect if they steal >> too many cycles.) >Hmm, that means splbio() is lower than spltty(), correct? That's a >genuine misunderstanding on my part. They're independent, but this isn't very relevant. spltty() only blocks tty software interrupts. I forgot that IDE disks can interfere with serial communications if they prevent the tty software interrupt handlers from running for more than about 20 msec - the low level buffer space runs out. If this happens then you may have more things to worry about - timeout routines would also be delayed for 20 msec, and it is a short step from there to the system spending all its time in the kernel. Bruce
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