On Monday, April 24, 2023 at 11:31:39 PM UTC-4, gah4 wrote:
> It seems that TOPS-10 gets an interrupt for every character typed, and that if you type fast enough, possible to overflow some buffer.
> The story I heard was that there was someone who could type that fast. (I believe a Diablo terminal at 300 baud.)
Yes, both TOPS-10 and Tops-20 could run into this. Tops-20 at least had the TRMOP bits that could be set to
let the front-end PDP-11 just echo simple characters. But teco and later tv, would change the action of printable
characters based on whatever mode you were in.
I don't think human typists could actually trigger it. (I did have a systems programmer who was trained as a classical pianist, he could really press the keys, he could type 200 words per minute, which was very fast). But in the last 70s, a lot of vendors
moved from simple glass teletypes like the VT52, VT100, ADM-3, etc. and supported a "forms" based display
with prompts and blanks for entering business forms. Most of these just buffered up the input, and submitted it all at 1200 or 2400 bps when you hit enter. This could over run the processing unless the form submission supported X-on/X-off (^S ^Q)
Other systems, like the HP3000 used a more sane protocol, the "enter" sent a string to the host, which would allocate a 2000 byte buffer, and then tell the terminal to dump its local buffer down the serial line.