On Sat, 20 Jun 1998, Ward Donald Griffiths III wrote: Weeelllll.... let's do some Research. From "The Annals of the Computation Laboratory of Harvard University", vol XVI, 1948.... one can find a few references to what we would term 'clock speed' in the descriptions of the various machines (the IBM ASCC Mark I, the ENIAC, Bell Telephone's Relay Computing System, the IBM Dahlgren Calculator Mark II). The Mark I "...operates at a speed of 200 cycles per minute." I make this to be over three cycles per second... and by cycles is meant *machine* cycles... I would posit an engineering-educated guess that the actual timing pulses were coming along a few multiples faster than this, though the description does not call out the actual master timing freq. The ENIAC, of course, was all electronic, but for example it's clock ran at 100 kHtz, with a duration of 2uSec. Bell Labs does not specifically say a clock rate, or any operational speeds, but the I/O were Teletype tape transmitters and Model 15 page printers. You do the math. (note: this article is full of cool pictures and examples of coding instructions and tables. If there's interest I could maybe do some scanning and uploads to my webpage.....) The Mark II Calculator was faster than the Mark I (and much bigger). Some timing references: "There are 100 storage registers in the entire machine. Any quantity standing in one of these is available to the computing parts of the machine in 33 milliseconds." "There are about 13,500 electro-mechanical relays in the Dahlgren calculator. The operating times of these relays in either direction are from six to ten milliseconds." "....cam operated contacts, about 800 in number, are used for this purpose. [the cams sync the machine and carry the heavy currents, sparing the delicate relays] The impulses...... are of 16 2/3 milliseconds in duration. A large margin of safety is thereby provided.." SO: The first American relay machines operated at speeds considerably in excess of 1 Htz. I have no data on the Zuse. neener neener neener, Ward ;} Trivia: The first Binary Adder was built by two Bell Labs engineers in the mid thirties, and called the "K2" because it was assembled one a Kitchen table in thier free time. I will look up the reference if anyone's interested. I really must scan the pix of the Mark II... they have a fish-eye shot of the whole machine, and also the various units, and even one of inside the relay cubicles... tres cool, no? Oui? Cheers John