I used one back around 1963-1965. Also used it's predecessors the vacuum tube based IBM 709 and the transistorized version of it, the IBM 7090.
The 7094 was what would now be called a 500 KHz (yes, kilohertz!!!) machine. But, it had a 36-bit word and all the basic instructions were performed in one cycle.
The standard machine had 32K words of core memory. The address field part of the machine instructions was 15-bits so its nor possible to address more memory. However, MIT paid IBM to have a second bank of 32K word memory with a machine instruction to switch which memory bank was active.
Great times!