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From: schwalbe@encore.UUCP
Newsgroups: comp.sys.ibm.pc
Subject: Re: watch out for install program in LIm EMM 4.0
Message-ID: <2174@encore.UUCP>
Date: Tue, 10-Nov-87 09:09:52 EST
Article-I.D.: encore.2174
Posted: Tue Nov 10 09:09:52 1987
Date-Received: Thu, 12-Nov-87 20:57:55 EST
References: <327@ndcheg.UUCP>
Reply-To: schwalbe@encore.UUCP (Jim Schwalbe)
Organization: Encore Computer, Marlboro, MA
Lines: 32
Keywords: LIM, EMS, install, intel
Summary: don't write to disk in turbo mode!



Be forewarned, DO NOT do anything which writes to the hard drive when you
are in turbo mode on your PC clone.  Most of the time it will work with no
trouble. Twice in the last year I had the same problem you did. After
doing something which wrote to the hard disk when I was in turbo mode, I
got an error message, BAD FAT!  The first time it happened, I did what you
did, I reformatted the disk since I didn't have much on it and just
shrugged my shoulders.  The second time it happened, I went in and
explored the FAT with Norton Advanced Utilities (has a nice FAT editor).
My first thought was that I had fallen victim to a "Trojan" but more
careful thought revealed the real problem.  About half a sector of the FAT
had all its data shifted one up?  I looked at what the extra inserted byte
was and sure enough it was the same as the first shifted byte.  Aparently
one of the bytes written to the disk had been double clocked.  Anyway,
after about an hour I fixed the problem by shifting everything back.  The
lesson I learned is not to write to the hard disk in turbo mode.
Curiously, I went back and looked in the manual that came with my clone
and sure enough, they state that programs like diskcopy, copyiipc, and a
few others won't work properly in turbo mode.  My bet is that the timing
to the disk controller doesn't make worst case at 8 MHz so spurious errors
can occur.  Have any other clone users seen this problem in turbo mode?
I'll bet it's a generic problem although it could be the type of hard disk
controller we're using (mine is a Microtek).

.---------------------------------------------------------------------------.
: Jim Schwalbe               .----------------. Mail: {linus,allegra,ihnp4} :
: Hardware Research Group .--+-------------.  |       !encore!schwalbe      :
: Encore Computer Corp.   |  | E N C O R E |  |                             :
: 257 Cedar Hill Street   |  `-------------+--' Phone: [617] 460-0500       :
: Marlborough, MA  01752  `----------------'                                :
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