Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!usc!ucsd!ucsdhub!hp-sdd!hp-pcd!hpcvra!prestonb
From: prestonb@hpcvra.CV.HP.COM (Preston Brown)
Newsgroups: comp.sys.handhelds
Subject: Re: SPEED vs FAST question (HP28S)
Message-ID: <21580002@hpcvra.CV.HP.COM>
Date: 22 Feb 90 17:57:22 GMT
References: <4282@rouge.usl.edu>
Organization: Hewlett-Packard Co., Corvallis, OR, USA
Lines: 17

>What exactly does FAST do (I mean, does it directly affect OS
>software or hardware operation) 

Fast writes to a hardware register which controls the speed of 
the main system clock.  The main clock is generated by using
the time base clock (32.768KHz) as a reference and a special
circuit to generate a main clock of 4MHz.  The control register
specifies the multiplication factor to use.

The FAST programs I have seen all set the main clock to the maximum
speed of 8MHZ.  While this works just fine in most cases, it is
operating outside of the product spec.  When your battery voltage
is low, it may fail; most likely resulting in a locked up machine and
memory lost.

The system is speced to operate at normal speed, > 3V , and a temp of
0 deg C to 40 deg C.