Epson GT-6500 EN - Manual (Page 91)

Problem:
After connecting a scanner with a higher function level than the
previous scanner, the new scanner does not operate properly.
Cause
Although you used the ESC I command to obtain the
function level information, your program was set up
to work only when the function level was the same
as the previous scanner.
Solution
EPSON scanner function levels are designed so that
higher levels encompass all the commands of lower
levels. Change your program so it works with
scanners of equal level or higher.
Problem:
The speed of image data transfer remains the same, whether you
use a SCSI or bi-directional parallel interface.
Cause
Your program is writing each line of image data to
your hard disk as the data is received.
Solution
When using scanners of B4 level or higher, always
use block data transfer.
Command Usage 2-53