Date: Sat, 12 Aug 1995 03:12:12 -0700 (PDT) From: "Rodney W. Grimes" <rgrimes@gndrsh.aac.dev.com> To: smp@teal.csn.org (Steve Passe) Cc: jayk@rahul.net, hardware@freebsd.org Subject: Re: Upgrade to my machine Message-ID: <199508121012.DAA05664@gndrsh.aac.dev.com> In-Reply-To: <199508112105.PAA29000@clem.systemsix.com> from "Steve Passe" at Aug 11, 95 03:05:18 pm
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> > > Hello, > > On Fri, 11 Aug 1995, Jay Kirchhoff wrote: > > >I thing IBM has a drive like that. It had two 2 gig 3.5 drives mounted > >in a full height frame. The ad said the two drive were addressed as one > >and the data was stripped across them. > > No, the ad I (think) I saw was for a discrete drive. Really not sure > why drive makers haven't done this years ago, there are already > multiple heads (1 per surface), and they are already > 'spindle-synced'. The cost would be duplication of head read/write > circuits and some additional combiner silicon. The biggest reason they have not done this is there is 1 analog preamp that sits on the actuator arm with an analog CMOS mux to switch between heads. Adding 3 or 7 amplifiers would be a signficant amount of mass on the actuator causing problems, and putting it farther away causes signal problems. You would also seriously increase the cross talk problems in the head to drive electronics cable when you started to run 4 or 8 analog 50MHz + data streams down it. This is a very low voltage high frequency transmission line and it is hard enough to make 1 work in a strip line design without stacking 3 or 7 more next to it causing noise. These are solveable problems, but they are expensive and complicated to solve. -- Rod Grimes rgrimes@gndrsh.aac.dev.com Accurate Automation Company Reliable computers for FreeBSD
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