From: utzoo!decvax!ucbvax!info-cpm
Newsgroups: fa.info-cpm
Title: Re: USER # in BIOS
Article-I.D.: ucbvax.482
Posted: Thu Dec 23 00:40:42 1982
Received: Fri Dec 24 04:13:23 1982

>From Eldridge.ES@Parc-Maxc  Thu Dec 23 00:28:49 1982
In-Reply-To: Mead's message of 21 Dec 1982 1102-PST
To: Dick <Mead@Usc-Eclb>
Cc: info-cpm@BRL
Via:  Parc-Maxc; 22 Dec 82 11:40-EST
Via:  Brl; 22 Dec 82 12:17-EST
Via:  Brl-Bmd; 22 Dec 82 12:50-EST

The error you describe is common to many CBIOS implementations and is an
annoying bug.  The proper solution is to save the value at location 4 and use it
as the currently logged drive on a warm boot.  Location 4 contains both the
current logged-in drive and the user number.  The warm boot routine should
save location 4, read in the CCP, then put the saved location 4 value into the C
reg and jump to the CCP.

Another idea I have been toying with is to run a checksum on the CCP
whenever a warm boot is requested, and only load the CCP if it has been over-
written.  This would have the advantage that ^C would log-in a new disk even
if the disk did not have CP/M on it (providing, of course, that the CCP was still
intact).

George