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Use Caution when copying LMFS partitions (XL400/1200 Block Size)

    Date: Thu, 9 Apr 1992 13:02 EDT
    From: sobeck@STONY-BROOK.SCRC.Symbolics.COM

	Date: Thu, 9 Apr 1992 02:16 PDT
	From: p2@porter.asl.dialnet.symbolics.com (Peter Paine)

	    Date: Wed, 8 Apr 1992 18:23-0000
	    From: smith@icat.larc.nasa.gov (Steven L. Smith)

	    I want to save my lmfs.file.1 (not a file WITHIN the LMFS) file, however,
	    I need to set the byte size in the file attribute. What is the byte
	    size of a block for a XL400/1200? It's not the same for 3600 machines.

    You mean the Length in Bytes attribute, accessible from dired by hitting the period key.

	    Steve Smith                          | Internet: smith@icat.larc.nasa.gov
	    NASA Langley Research Center         |
	    M/S 152                              | Voice: (804) 864-2004
	    Hampton, VA 23665                    | FAX  : (804) 864-7793

	Do a Dired of your Fep, pick the largest world.
	Divide the world byte size by its block size.

	For the 36xx machines (36 bit) (World - Genera-8-1)
	  (floor 40950144 35547) => 1152
	For Ivory machines (40 bit)
	  (floor 51759360 40437) => 1280

	Double check that you have not been doing funny things with the number
	base on the machine (ie. everything is in decimal).

    The length of a FEP block  is the number words addressable by one byte, or 256 words.  
    For an Ivory-based computer, with its 5 byte word, this is 1280.  For a 36XX, which has 
    an even more exotic 4.5 byte word, a FEP block is 1152 bytes.

If you are writing software for this task, it is best not to hardwire
these constants.  Use (* SI:DISK-SECTOR-DATA-SIZE32 4) to get the number
of 8-bit bytes per block for the machine the code is compiled for.