Today was rather impressive, in the span of 4 minutes the S&P dropped ~60 points, overall spread of ~100 points today between the high/low. Some comments I’ve come across:
“while bad this is nothing compared to 1987. i was a retail broker at the time. phone lines jammed. computers locked. ibm bid $90 / ask $120 that day.” Bromhead on slope
“The panic in the middle of the day was market makers that just disappeared, and every machine on Wall Street was trying to sell into a market that didn’t exist. That was a bizarre electronic quant panic of people selling into a black hole. I don’t know if somebody pressed the wrong button, but the intraday was a panic machine-led move,” Peter Bookvar, U.S. market strategist at Miller Tabak.
And they managed to keep the machines running the whole time “during the market’s brief 900-point plunge” NYSE: No techical glitches as market declined
And for future reference, “The new Buy Like Hell Zone is 9% below the previous day close… just before the circuit breakers kick in and shut the markets down. 
” Iguanadon on slope