SUBJECT : Disk dumps with IMP

FROM	: Irv Hoff

DATE	: 01 June 87



	The distribution copy of IMP sets the file transfer disk buffer
to 16k.  This is one "file extent" in length.  (MODEM7 used to dump
every 2k, MDM7 every 16k.)  Minimizing the number of disk dumps helps
to increase the efficiency of a file transfer.

	Should you notice an error frequently occurs every 128 records,
it is likely caused by your small floppy disk taking over 10 seconds to
dump 16k to disk.

	The solution is simple.  Change byte 0BFF from 80H (128 decimal
for 16k) to perhaps 40H (64 decimal for 8k).  This byte is easy to re-
member as it is one less than 0C00, where the telephone library starts.
It was placed at this position just so it could be easily found.

	You can also use the I2NM-2.ASM telephone overlay and change the
label XFRSIZ from 16 to 8.  Then use MLOAD.COM to merge that overlay
onto the main program.	This may be easier for you than using DDT.

	Since only a few people have this problem it seemed better to
tell them, rather than penalize those with faster disk system by making
it 8k for everybody.  (The name of the game is to minimize delays - this
is the main reason for adding 1k block sizes, going to 2400 bps modems,
etc.)

 	 NOTE:  The 1571 disk system used with the
		Commodore C128 is exceptionally slow.
		The I2C8-x.ASM overlay for this com-
		puter has an option included to set
		the disk dumps to 4k.

					- Irv Hoff
					  Los Altos Hills, CA
					  (415) 948-2513 PRACSA RCPM
					  (415) 948-2166 voice