Looks like John beat me to it ;-) Steve played with expanding the buffer a long time ago while we were playing with the M100-on-the-Internet but never got it working 100% reliably, so we ended up handling XON/XOFF in the bridge hard/software instead which could respond instantly.
m ----- Original Message ----- From: John R. Hogerhuis To: Model 100 Discussion Sent: Monday, October 17, 2016 5:05 PM Subject: Re: [M100] mComm 1.5 On Mon, Oct 17, 2016 at 1:11 PM, Kurt McCullum <kurt.mccul...@att.net> wrote: John, Thanks for info. Is that a TELCOM limit? The reason I ask is because when running virtual T with TS-DOS, I notice that the buffer can go to 255. Or at least the byte which holds the buffer size. In my experience I've found that all 8-bit bytes go to 2^8 - 1 = 255 Just teasing :-) It could but it should never in practice have a value > 64. Have you observed a higher value than 64? It's not a limitation of TELCOM per se, it's a limitation of the receive interrupt handler logic and the size of the circular queue-on-array reserved for receiving bytes. The same receive handler is used for TELCOM and BASIC access to the serial port. See http://www.club100.org/ftp/m100-hiddenpowers-3.pdf Page 186 It shows a receive buffer of 64 bytes. If it went beyond the bounds, unmasked, I would expect it to corrupt other data structures. The high-water mark for the buffer is 40 (the point at which the receive handler sends XOFF), which probably makes more sense in the context of a 64 byte buffer than a 255 byte buffer :-) -- John.