The ALWAC III-E was an early commercial vacuum tube computer employing a rotating magnetic drum main storage unit.
The invention of the ALWAC III-E is attributed to Axel Wenner-Gren, and the name is derived from Axel Leonard Wenner-Gren Automatic Computer. The ALWAC III-E contained 132 - 275 vacuum tubes, 5000 - 5400 silicon diodes, and cost $60,000 - $80,000. Word size was 32 bits + sign + recoverable overflow bit.
Instruction execution times (including average memory access times) were 5.25-5.75 milliseconds for addition and subtraction, and 21.25 ms for multiplication and division.
An ALWAC III-E was installed at the University of British Columbia in March 1957 and remained in service until October 1961. Another was installed at Oregon State University (then College).
Memory
"The arithmetic registers of the ALWAC computer are circulating loops of information one word in length. The information is changed when the magnetic writing head is switched to an input device or to some reading head other than the one which makes up the loop with it. In addition to four one-word registers, the drum has four 32-word channels of working storage from which instructions are picked up to be carried out and data picked up to be operated on in the arithmetic registers. The working storage, through what is essentially a loop arrangement, has faster access than the remainder of the drum, the main storage.
"Main storage consists of 128 channels, 32 words in each. Any main-storage channel may be copied in a block to one of the working-storage channels, and a working-storage channel may be copied in a block to any main channel."