TITLE
    DOS Compatibility Card: DOS SCSI Drive Retry Error (3/95)
Article ID:
Created:
Modified: 		17353
3/13/95
5/24/95
TOPIC



    I have a DOS Compatibility Card and I have installed a DOS formatted SCSI hard drive on my Macintosh. When I switch to MS-DOS and attempt to read or write to the DOS SCSI drive, I frequently get "X: Drive Unavailable" errors, Drive retry errors, and general protection errors. Why do I get these problems so often?

DISCUSSION


    To find out what is causing the problem, first turn off filesharing in the Mac OS. Restart the DOS Compatibility Card and try to access the programs you had problems with. While doing this, do not insert any floppy disks and make sure nothing in the Mac OS is accessing the hard disk. You should also run CHKDSK or SCANDISK to make sure the drive media, file allocation tables and directory structure is in proper working order. If CHKDSK and SCANDISK do not find problems, the errors you are receiving may be related to the fact that only one operating system can access the SCSI bus at one time. If you are working in DOS/Window and some Macintosh operation needs to read or write to the SCSI drive, the Mac OS has priority and forces the DOS/Windows software to wait. This can cause the errors you mentioned. If filesharing is on and someone is accessing your hard disks while a program on the DOS/Windows side is reading or writing to its SCSI drive, it is forced to wait for the Mac OS to complete its tasks. In some cases, if you insert a floppy disk while DOS/Windows is doing a read or write, the Mac OS again takes precedence and force DOS/Windows to wait, sometimes causing the errors you described. In most cases, selecting "retry" may allow the DOS/Windows program to access to the SCSI resources it is trying to read or write to. However, DOS/Windows still has to wait for the Mac OS to finish using the SCSI bus.

    If you have a problem starting up windows or you are getting errors with the windows swap file (sometimes its OK and Windows just thinks it's corrupted), examine the same items discussed above. Remember, the MacOS has priority over the SCSI Bus and if Windows is trying to startup using its files while a Mac OS application is reading or writing, Windows is forced to wait causing an error.


    Article Change History:
    30 Mar 1995 - Corrected Mac OS name.

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Document Information
Product Area: Computers
Category: DOS Compatible
Sub Category: DOS Compatibility Cards
Keywords: kwindows

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