On Mon, Apr 27, 2020 at 5:16 PM Stephen Adolph <twospru...@gmail.com> wrote:
> Interesting. > So I have some data now for TPDD transfer @76800, 38400 and 19200. > 32kb transfer from PC to M100 (actually writing to ram sequentially) > 76800 == 9 sec > 38400 == 14 sec > 19200 == 23 sec > > strange though, I have my 56800 result @ 7 sec. weird. > > Unless my code is very inefficient, it seems that TPDD protocol overhead > really slows things down, because TBACK was able to do the same at 6.6 sec. > > Maybe TBACK is the right way to go here, and abandon TPDD protocol for > large transfers.. > > > Maybe, maybe not. TBACK is it's own special animal closely tied to the M100 ROM. Yeah TBACK streams data as fast as the machine can go. It does no acknowledgements or checksums. TBACK assumes the communication channel is perfect. Which in general a RS232 cable connection seems to be. In practice I've found that it holds up. Now if you're going over a telephone line and modem that's a horse of a different color. I feel that the happy medium would be Zmodem to replace TPDD protocol. Zmodem is able to support streaming data while sending ack's and checksums asynchronously and/or over much larger byte ranges. This can get pretty close to the speed of the channel while adding some peace of mind with the checksums. As to why your code 57600 is faster than 76800, I don't know. I am still curious why you had to do something to the FTDI driver to get it to allow 76800. I never had to do that. -- John.
