Foonlies

If you are comparing 74S/AS/F TTL to 10K ECL, you are making a unfair comparison. When the 74S and 10K were introduced in the very early 1970s, 10K ECL was not the fastest ECL available, MECL III was. MECL III was almost three times faster than 10K, but was expensive and difficult to use. It remained in front line use until the mid-1970s, simply because nothing could touch it. 10K became the popular ECL family because it was the easiest to use and would not break the bank. Additionally, when 74AS was introduced, 100K had already been established, with 10KH following shortly thereafter. 100K was very easy to deal with, as long as ALL the rules in the databooks were followed, but like MECL III, very expensive (a normal glue logic chip, like a 100101 triple OR/NOR was seven bucks in DIP, compared to thirty cents for something similar in TTL). Later still, 10E/100E was even faster, down to typical 400 pS gate delays - still something that TTL could not touch at the time. To top in off, 10G was a little faster that 10E/100E. Also, running 74S at full throttle often results in a real shitshow on the circuit board. It is far easier to run ECL at full speed potential. CMOS killed ECL, not TTL. -- Will