From nwsgrp@ntlworld.com Tue Jun 5 20:16:27 2007 Path: ewrotcd!?@127.0.0.1!feed-ewrotcd!gemini.csx.cam.ac.uk!news.cam.ac.uk!feed4.jnfs.ja.net!jnfs.ja.net!zen.net.uk!hamilton.zen.co.uk!proxad.net!feeder2-2.proxad.net!62.253.162.218.MISMATCH!news-in.ntli.net!newsrout1-win.ntli.net!ntli.net!news.highwinds-media.com!newspeer1-win.ntli.net!newsfe1-win.ntli.net.POSTED!53ab2750!not-for-mail From: S G Newsgroups: comp.sys.acorn.hardware Subject: Re: converting PC floppy drive to ID 0 ? References: <%yF8i.7973$rW2.4068@newsfe7-win.ntli.net> Organization: - X - Lines: 51 X-Newsreader: Messenger 1.41d for RISC OS Message-ID: <0070-2-0.20070603.224549.24@ntlworld.com> User-Agent: NewsHound/v1.50-32 Date: Sun, 03 Jun 2007 21:46:41 GMT NNTP-Posting-Host: 82.6.74.176 X-Trace: newsfe1-win.ntli.net 1180907201 82.6.74.176 (Sun, 03 Jun 2007 22:46:41 BST) NNTP-Posting-Date: Sun, 03 Jun 2007 22:46:41 BST Xref: news.chiark.greenend.org.uk comp.sys.acorn.hardware:51308 Here's what Kevin Bracey wrote some time ago: The original "standard" floppy interface (as used by current RISC OS systems) uses 4 drive select lines and a shared motor enable line: DS1 pin 10 DS2 pin 12 DS3 pin 14 DS4 pin 6 MOT pin 16 The idea is that the drives should have a switch/link to choose which DS line they act on. Support for drives 3 and 4 is rare - I'm not sure that RISC OS machines have ever actually wired them up. The A5000 did support 4 drives, but on 2 connectors, each of which used DS1 and DS2. Floppy drives designed for PCs are set to use DS2, but they still use the standard MOT pin. The PC motherboard connector has: DS1 pin 14 DS2 pin 12 MOT1 pin 10 MOT2 pin 16 The twist in the cable swaps pins 10-16 and pins 12-14, so that DS2 and MOT2 are monitored by the drive before the twist, and DS1 and MOT1 are used by the one after the twist. The benefit of the PC scheme is independent motor control, and no links on the drives. The disadvantage is an ugly cable, which requires a twist even with 1 drive, and being limited to 2 drives (unless you have a buffer board which uses an encoding as specified in the ADFS section of the manual). Anyway, the upshot is that the only swap required to get a PC drive without a switch to look like a "normal" drive 0 should be to swap pins 10 and 12 (or find a link on its PCB that does this). In addition, it's only the Risc PC Mk 1 which doesn't have DS2 routed to the connector that wouldn't find a single DS2 drive anyway. ADFS searches the drives from DS1 to DS4 until it's found the number of floppies specified by *Configure Floppies - whichever drives are found become ADFS drives :0 upwards. There were other complications to do with thinks like Ready and Disk Changed lines, but I think they're now standardised for all modern drives. -- Stewart Goldwater http://janusg.co.nr