The other 9 units in ENIAC were the Initiating Unit (started and stopped the machine), the Cycling Unit (used for synchronizing the other units), the Master Programmer (controlled "loop" sequencing), the Reader (controlled an IBM punch-card reader), the Printer (controlled an IBM card punch), the Constant Transmitter and 3 function tables.
According to a 1989 interview with Eckert, "We had a tube fail about every two days and we could locate the problem within 15 minutes." In 1954, the longest continuous period of operation without a failure was 116 hours—close to five days.
Numerous 6L6s and 6V6s served as line drivers to drive pulses through cables between rack assemblies.
Several tubes burned out almost every day, leaving ENIAC nonfunctional about half the time.
It had a speed on the order of one thousand times faster than that of electro-mechanical machines; this computational power, coupled with general-purpose programmability, excited scientists and industrialists alike.
This combination of speed and programmability allowed for thousands more calculations for problems, as ENIAC calculated a trajectory that took a human 20 hours in 30 seconds (a 2400× increase in speed).