Editing EDVAC (section)

==Technical description==
The EDVAC was a [[Bit-serial architecture|binary serial computer]] with automatic addition, subtraction, multiplication, programmed division and automatic checking with an ultrasonic serial memory<ref name="Wilkes"/> capacity of 1,024 44-bit words, thus giving a memory, in modern terms, of 5.6 [[kilobyte]]s.<ref>[http://ed-thelen.org/comp-hist/BRL61-e.html#EDVAC BRL report 1961]</ref>

Physically, the computer comprised the following components:
* a [[magnetic tape]] reader-recorder (Wilkes 1956:36<ref name="Wilkes"/> describes this as a [[Wire recording|wire recorder]].)
* a control unit with an [[oscilloscope]]
* a dispatcher unit to receive instructions from the control and memory and direct them to other units
* a computational unit to perform arithmetic operations on a pair of numbers and send the result to memory after checking on a duplicate unit
* a timer
* a dual memory unit consisting of two sets of 64 [[mercury (element)|mercury]] acoustic delay lines of eight words capacity on each line
* three temporary delay-line tanks each holding a single word<ref name="Wilkes"/>

EDVAC's average addition time was 864 microseconds (about 1,160&nbsp;operations per second) and its average multiplication time was 2,900 microseconds (about 340&nbsp;operations per second). Time for an operation depended on memory access time, which varied depending on the memory address and the current point in the serial memory's recirculation cycle.

The computer had 5,937 [[vacuum tube]]s and 12,000 [[diode]]s, and consumed 56 [[kilowatt|kW]] of power. It covered 490&nbsp;ft² (45.5 m<sup>2</sup>) of floor space and weighed {{Convert|17,300|lb|ST MT}}.<ref>{{Cite web|url=http://ed-thelen.org/comp-hist/BRL-e-h.html#EDVAC|title=EDVAC|last=Weik|first=Martin H.|date=December 1955|website=ed-thelen.org|series=A Survey of Domestic Electronic Digital Computing Systems}}</ref> The full complement of operating personnel was thirty people per eight-hour [[shift work|shift]].

EDVAC could also do [[floating-point arithmetic]].  It used 33 bits for the [[Significand|mantissa]] and one bit for its sign.  It used 10 bits for the power of 2, including the sign bit.

For executable instructions, the 44-bit word was divided into four 10-bit addresses and four bits to encode the index of an operation.  The first two addresses were to the numbers in memory being used in the operation, the third address was for the memory location to store the result, and the fourth address was the location of the next instruction to be executed.  Only 12 of the possible 16 instructions were used.