JRD@cc.usu.edu (Joe Doupnik) (01/03/90)
Just to and yet another word to the "discussion" on protocol file transfer programs, this time on the foreground graphics vs background comms point. There's hope! National Semiconductor has a new UART chip NS16550A which has a 16 character receiver fifo. And what a difference that makes to losing characters! The chip can generally be plugged into an 8250 socket and do the job old-style with no changes anywhere. However, the gotcha is an applications program needs to engage fifo mode explicitly; MS Kermit v3.0 does so. The chips cost me about $26 apiece, the NS16550A, not a NS16550 which has bugs preventing use of the fifo (early runs of PS/2s reputedly had to settle for 16550's). When properly programmed for fifo mode in MS Kermit I ask it to generate an interrupt when either 8 characters have arrived or when fewer are present but 4 char times have elapsed (a fast timeout). I has allowed me to boost the speed of MSK to MSK transfers to 115KB from 386 to old 8 MHz AT on a very short wire (an RS232 problem, not a programming one). Previously the hard disk controller and/or video display would keep interrupts off too long and a character would be lost; very infrequent now. The effective file characters/second rate is limited by the cpu+disk performance to around 4000++ characters/sec (over 40KB); 386 to 386 is faster. But then speed is not everything. Joe D.