Path: utzoo!mnetor!tmsoft!torsqnt!lethe!yunexus!ists!helios.physics.utoronto.ca!news-server.csri.toronto.edu!bonnie.concordia.ca!ccu.umanitoba.ca!umrobbin From: umrobbin@ccu.umanitoba.ca Newsgroups: comp.sys.m6809 Subject: Coco Drive Select 4 Message-ID: <1991Feb8.101626.23735@ccu.umanitoba.ca> Date: 8 Feb 91 10:16:26 GMT Organization: University of Manitoba, Winnipeg, Canada Lines: 29 I know this isn't an official Coco forum, but it'll have to do... I need to know how the Coco handles the drive selects. We have here four disk drives, three of which we have connected with no problem, but the fourth drive (i.e. drive 3 under RSDOS) is giving us problems. On my old old drive controller, there are three pins pulled on the drive end of the cable. Two of these are drive selects for drives 1 and 2, but the third is, according to all information I have, the side select line. Long ago someone told me that Cocos used side select for the fourth drive select, but as far as I can tell this isn't true (side select goes active for ALL drives, while selects 0,1,2 all behave correctly). This is also the case for a newer controller we tested. So the only way I can figure out to select the fourth drive is to wire a chip to detect SS active with DS0-DS2 inactive. Is this the way its done? (If so, why on earth is it done this way instead of using the fourth drive select like the other computers in the world?) What is the SS line tied to? If it is tied to a side select output on the controller chip, will a more intelligent DOS (OS9?) be able to handle three double sided drives? Steve Robbins