Xref: utzoo comp.os.os9:1441 comp.sys.m6809:1370 Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!sun-barr!lll-winken!ncis.tis.llnl.gov!dog.ee.lbl.gov!hellgate.utah.edu!fcom.cc.utah.edu!cc.utah.edu!cc.usu.edu!slsw2 From: slsw2@cc.usu.edu Newsgroups: comp.os.os9,comp.sys.m6809 Subject: Re: adding as disk drive to COCO3 Message-ID: <1991Jan25.154150.46743@cc.usu.edu> Date: 25 Jan 91 21:41:50 GMT References: <523@ctycal.UUCP> <1991Jan21.180211.11345@mentorg.com> Lines: 47 In article , avalon@coombs.anu.edu.au (avalon) writes: > dclemans@mentorg.com (Dave Clemans @ APD x1292) writes: > >>From article <523@ctycal.UUCP>, by ingoldsb@ctycal.UUCP (Terry Ingoldsby): >>> There is nothing you can do to fix the controller, you must slow down the >>> drive. Most 1.2 MByte disk drives use motors that have two speeds. >>> Sometimes there is a jumper, sometimes a wire that must be disconnected >>> to select 300 RPM. Do this and you will suddenly have a working drive. >>> Your storage will only be about 700K, *not* 1.2 MByte. >>> > >>To clarify things, 1.2 Meg drives DO NOT!! spin faster than other drives. >>The disk moves at EXACTLY the same speed. > >>The difference between them is in the electronics. 1.2 Meg drives are clocked >>twice as fast as the slower drives. Controllers that can handle both drives >>have the ability to switch clock rates. > > I have run a 1.2MB drive on my coco while using some utility program > that shows disk rotation speed in RPM/ 1.2 drives go around at about > 360+rpm and 720K drives at about 300 rpm (same as 360K drives). 1.2 meg drives spin at 360 RPM because that's how fast 8" drives spun and a 1.2 meg drive has the same characteristics of an 8" drive. Really. IBM's original AT drive could not change speed, so it ran at 360 RPM regardless of the data rate. That's why an AT controller does 250 KHz, 500 KHz, and 300 KHz data rates; 250 is normal, 500 is 1.2 M, and 300 is normal in a 360 RPM drive. Good drives (TEAC FD55's, for instance) will change speed so that the disk controller only has to handle 500 KHz and 250 KHz. Oh yeah. I've noticed a tendency for PC drives to have the drive select jumpers soldered in at DS 1 since *everyone* has an AT and therefore *everyone* uses a twist in the cable so that all the drives are jumpered at DS 1. Being an old CP/M guy, this drives me nuts. Don't mind me; just passing through... -- =============================================================================== Roger Ivie 35 S 300 W Logan, Ut. 84321 (801) 752-8633 ===============================================================================