Wikipedia
DYSEAC
DYSEAC was the second Standards Electronic Automatic Computer. (See SEAC.)
DYSEAC was a first-generation computer built by the National Bureau of Standards for the US Army Signal Corps. It was housed in a truck, making it one of the first portable computers (perhaps the first). It went into operation in April 1954.
DYSEAC used 900 vacuum tubes and 24,500 crystal diodes. It had a memory of 512 words of 45 bits each (plus one parity bit), using mercury delay line memory. Memory access time was 48–384 microseconds. The addition time was 48 microseconds and the multiplication/division time was 2112 microseconds. These times are excluding the memory access time, which added up to approximately 1500 microseconds to those times.