Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site phri.UUCP Path: utzoo!watmath!clyde!burl!ulysses!allegra!mit-eddie!genrad!panda!talcott!harvard!cmcl2!phri!roy From: roy@phri.UUCP (Roy Smith) Newsgroups: net.periphs Subject: SMD vs. MCSP, Unibus vs. Massbus vs. SBI: Does it matter? Message-ID: <505@phri.UUCP> Date: Wed, 2-Oct-85 20:50:47 EDT Article-I.D.: phri.505 Posted: Wed Oct 2 20:50:47 1985 Date-Received: Sat, 5-Oct-85 15:10:17 EDT Distribution: net Organization: Public Health Research Inst. (NY, NY) Lines: 28 Keywords: disk controller-to-drive interface, performance evaluation We're looking into buying a whole new I/O system for a used 11/780 we might be getting (it has old disks which we want to loose). Is the type of interface between the controller and the drives something I should worry about? Other than MCSP-style coax cables being nicer to deal with than SMD-style flat cables, are there any inherent advantages to MCSP over SMD drives? Assuming similar drive specs (seek time, RPM's, geometry), will having one type of interface improve disk sub-system performance over the other? How far does the MCSP spec go? Is it just the controller/drive interface, or does it also imply UDA-50 emulation on the Unibus? Somewhat orthogonal to the above questions, how much difference will I see between a Unibus disk and the same drive on a Massbus (or directly on the CMI/SBI bus)? I've read so many different bandwidth figures for the various busses, I'm inclined to believe none of them. Also, how much of a factor is underlying bus bandwidth going to be on overall disk throughput? I realize these are broad questions, with answers depending on the specifics of the particular situation. What I'm really after is not so much an answer to "Which disk is best for me?", but a guide to what factors might go into the evaluation so I can come up with my own answer. -- Roy Smith System Administrator, Public Health Research Institute 455 First Avenue, New York, NY 10016 Brought to you by Super Global Mega Corp .com