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From: ballou@brahms (Kenneth R. Ballou)
Newsgroups: comp.sys.ibm.pc
Subject: Re: AT questions
Message-ID: <332@cartan.Berkeley.EDU>
Date: Mon, 17-Nov-86 16:15:44 EST
Article-I.D.: cartan.332
Posted: Mon Nov 17 16:15:44 1986
Date-Received: Mon, 17-Nov-86 22:30:31 EST
References: <13210001@acf4.UUCP>
Sender: daemon@cartan.Berkeley.EDU
Reply-To: ballou@brahms (Kenneth R. Ballou)
Organization: Math Dept. UC Berkeley
Lines: 53

In article <13210001@acf4.UUCP> mamon@acf4.UUCP (Gary Mamon) writes:
>Hi there!
Hello.

>We are interested in acquiring an AT clone, and looking at the literature
>brings up the following questions (and also shows the extent of my ignorance):
Better to ask the questions now.  And no, it does not show you to be ignorant!

>1. Why do some machines have two or more clock-times available? Shouldn't
>one want the largest clock rate when any choice is available?
Not always.  The vast majority of software will run at the higher speed.
However, some screwy copy-protection schemes will fail at the higher speed
and succeed at the lower one.  Also, some of the more inexpensive peripherals
become very unhappy at the higher speed.  For example, I have an internal
modem which works fine at 6 MHz but which is literally invisible to the system
at 12 MHz.  This is not unreasonable, since peripherals do not necessarily
expect to have the bus driven at such a speed, even if they aim to be IBM
compatible.  (What a thought, IBM coming out with a fast microcomputer!)

>2. Some advertisors indicate: "640k RAM on Motherboard". Is this memory
>THE memory of the machine, or does it simply indicate the amount which the 
>memory can be expanded to?
	Neither, exactly.  The AT's memory can be expanded to 16M, although
that won't do you a whole lot of good under current DOS (well, 15M worth of
RAM disks :-).  This tells you how much memory is in the machine when you
first take it out of the box.  
	To expand the memory beyond what is on the motherboard, you will need
to purchase an expansion card.  Usually these cards give you space to plug
in up to 3M of RAM chips.

>3. Can Xenix be run on any clone? Does it work well (i.e., is the total
>machine performance significantly reduced when two or more users or tasks
>are competing for CPU?).
	It works on my machine.  It's fairly good at 6MHz and an absolute joy
at 12 MHz.

	By the way, allow me to give you some unsolicited advice.  I have
a PC's Limited 286-12 and am thoroughly delighted with the machine.  I have
had literally *ZERO* difficulty with it and have found no compatibility
problems so far.  I wouldn't hesitate for a moment to recommend the machine to
you.

	I will, however, pass along one remark.  Don't forget that a higher
clock speed may upset some peripherals.  In particular, if and when you decide
to add memory to your system (and if you are running XENIX, you will), you
may find you need to get faster RAM than is used in 6 or 8 MHz machines.
Personally, I find the extra speed well worth it.

--------
Kenneth R. Ballou		...!ucbvax!brahms!ballou
Department of Mathematics	ballou@brahms.berkeley.edu
University of California
Berkeley, California  94720