Date   : Sat, 13 Nov 1982 00:30:00-EST
From   : Ronald G Fowler <RGF@Mit-Mc>
Subject: [RGF: when to log-in a new disk?]

Date: 13 November 1982 00:24-EST
From: Ronald G. Fowler <RGF>
To:   PLATTS at WHARTON-10
cc:   RGF, mknox at UTEXAS-11
Re:   when to log-in a new disk?

   Steve, your BIOS should relog a disk whenever its SELDSK entry is
called with a 0 in the E register; this bit is actually the "login
vector"
 rotated such that the requested drive's bit is in DE
least-significant-bit. This is not documented in the system Alteration
guide but is supported for all SELDSK calls in both CP/M 2.x, MP/M II
and CP/M III (so I'm told).  If DR had bothered to mention this in the
original documentation, disk-relogging problems like this would never
have come about.                       --Ron