24 Jul
2006
24 Jul
'06
3:15 a.m.
From "Parallel Port Complete" (1996) by Jan
Axelson:
If it's an ISA-bus adapter, the bus speed is essentially the limiting
factor, no matter what the type of port is. At an 8.33 MHz ISA bus speed,
that translates to about 1.3MB/sec. SPP, because of the requirement of 4
writes to do a handshake, can go at best 300KB/sec. ECP and EPP can move
at 1.3MB/sec because the handshake's done in hardware. If ISA shortened
cycle timings (0WS) are used, one can hit about 2.7MB/sec. If DMA is used,
this slows to about 1 MB/sec.
Somewhere, I've got a copy of the IEEE spec, but I don't know if it calls
out an upper lmit on transfer rates.
Cheers,
Chuck