Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!uwm.edu!ogicse!zephyr.ens.tek.com!orca.wv.tek.com!frip!andrew From: andrew@frip.WV.TEK.COM (Andrew Klossner) Newsgroups: comp.arch Subject: Re: Incremental sync()s and using disk idle time Message-ID: <10404@orca.wv.tek.com> Date: 22 Mar 91 00:25:00 GMT References: <1991Mar12.202238.19586@zoo.toronto.edu> <3254@crdos1.crd.ge.COM> <6707@hplabsz.HP.COM> Sender: nobody@orca.wv.tek.com Reply-To: andrew@frip.wv.tek.com Organization: Tektronix, Wilsonville, Oregon Lines: 20 [] "... your big expensive main host CPU will spend all its time waiting for the dumb little I/O controller ..." "This is only true if the dumb little I/O controller is not fast enough to keep up with the device it's controlling." It must also be fast enough to hold up its end of the conversation when it communicates with the host. I worked on a system with a 68020 host, talking over a SCSI channel to a disk whose controller used a Z8. There's a lot of back-and-forth in the SCSI protocol, and you could just about fall asleep waiting for that Z8. It was so slow that the 68020 spent some serious time waiting, but not so slow that it would have paid off to dismiss from interrupt at each step of the conversation. -=- Andrew Klossner (uunet!tektronix!frip.WV.TEK!andrew) [UUCP] (andrew%frip.wv.tek.com@relay.cs.net) [ARPA]