Date: Mon, 26 Aug 1996 11:02:18 -0700 (MST) From: Terry Lambert <terry@lambert.org> To: hal@post.vale.com (Hal Snyder) Cc: michaelv@MindBender.serv.net, freebsd-hackers@FreeBSD.org Subject: Re: Multiple swaps slow down system? Message-ID: <199608261802.LAA22844@phaeton.artisoft.com> In-Reply-To: <01BB932F.47934380@jaguar> from "Hal Snyder" at Aug 26, 96 09:15:14 am
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> > I don't know why that happens, but I wouldn't expect it to give you > > much of a performance boost, since IDE doesn't do asynchronous I/O (at > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > > least under *BSD anyway). If you have a very busy system, I would > > expect it to give you a performance drop, in fact. > > I'm not sure what you mean here by "asynchronous". Can you explain? > > The last time I looked at hd device drivers, SCSI had it all over IDE just > because of DMA support - the old ST506 interface still used by IDE forced the > CPU to handle all I/O going to/from the hard drive. Has this changed? Your CMOS will call it "overlapped I/O". Do not enable it for DOS, Win95, or NT if you value your disk contents, unless you are certain you do not have an RZ1000 about 33% of all IDE controllers that have been deployed) or the next most popular IDE controle (CT? CDS?) that are another ~27% of the market. Check out www.intel.com for detection programs that will tell you about whether or not your IDE controller is one of the ~60% that are broken for doing interleaved (or "ovelapped") I/O. If you installed a newer MS OS (NT 3.51 or better, or the refresh release of 95), then the install probably turned this off in the CMOS (silently, without telling you about it at all). Terry Lambert terry@lambert.org --- Any opinions in this posting are my own and not those of my present or previous employers.
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