Path: utzoo!utgpu!news-server.csri.toronto.edu!clyde.concordia.ca!uunet!sdrc!thor!scjones From: scjones@thor.UUCP (Larry Jones) Newsgroups: sci.electronics Subject: Re: hard disk stumpper Message-ID: <134@thor.UUCP> Date: 19 Aug 90 18:26:42 GMT References: <3967@newton.physics.purdue.edu> <1291@gold.GVG.TEK.COM> <15649@.la.locus.com> Organization: SDRC, Cincinnati Lines: 46 In article <15649@.la.locus.com>, dana@lando.la.locus.com (Dana H. Myers) writes: > In article hobbit@remus.rutgers.edu (*Hobbit*) writes: > >I installed a switch in my PC to deliberately open the write gate signal, > >and damned if it doesn't prevent the controller from scribbling on the disk. > > >Anyway, > >the fun thing about this hack is that the controller has no clue whether > >the write succeeded or not, and due to disk buffering, MSLoss really thinks > >the new file is there, and you can even type it; but the next time you do a > >DIR or something the buffers get flushed and the file mysteriously disappears. > > On MS-DOS, the shell (command.com) normally provides a command to > enable or disable verification of disk writes. This is the 'verify' > command. At the DOS prompt, issue the command 'verify'. You will be > notified of the current state of verification ('on' or 'off'). If it is > off, try setting it on; enter the command 'verify on'. This is a common misconception. When you enable VERIFY in MS-DOS it only verifies that what is on the disk is readable. It most definitely does NOT compare what it reads to what what written. The confusion is understandable given the terrible description given in most DOS references. For example, the MS-DOS Encyclopedia description of VERIFY refers to COPY/V which says (notes in [] are my comments): The /V switch causes a read-after-write verification of each block of the destination file [blatently misleading]. Its effect is equivalent to that of the VERIFY ON command [don't you just love circular definitions?]. No comparison is made between the source and destination files [finaly, the key phrase!] -- the /V switch simply causes MS-DOS to verify that the destination file has been written correctly [again somewhat misleading]. All that VERIFY does is call INT 13, Function 4, Verify Disk Sectors, which just verifies that the sector is readable, not that it contains any particular data. ---- Larry Jones UUCP: uunet!sdrc!thor!scjones SDRC scjones@thor.UUCP 2000 Eastman Dr. BIX: ltl Milford, OH 45150-2789 AT&T: (513) 576-2070 It doesn't have a moral, does it? I hate being told how to live my life. -- Calvin