HIGH SPEED MEMORY
The High-Speed Memory (HSM) in the RCA 301 System consists of 10,000, 20,000 or 40,000 characters. Each
10,000 characters consists of fourteen 50 x 100 matrices of magnetic cores. As each core represents one bit, a matrix
of cores represents 5,000 bits and a memory unit represents 70,000 bits. As each 301 character is made up of seven bits,
each memory unit can store 10,000 characters in 10,000 individual character locations.
Each location in memory has a unique address, consisting of four RCA 301 characters. Though oversimplified,
the HSM may be pictured as a rectangular array of locations, with the smallest address in the upper left-hand corner
and the largest address in the lower right-hand corner. The lowest address in the HSM is always 0000. The highest
address in a system with a 10,000 character memory is 9999. In the case of a 20,000 character memory the second
10,000 characters are addressed from &000 to 1999. In the case of a- 40,000 character memory, the third 10,000
characters are addressed from —000 to R999, and the fourth 10,000 characters are addressed from "000 to Z999.
If an address greater than the processor's maximum memory location is specified, a Memory Register Parity Error
alarm will occur and stop the Computer.
The HSM is constructed so that two characters (14 bits) in consecutive memory locations are accessed in a
single memory cycle. The computer cycle is 7 microseconds; this means that characters may be addressed, brought
into the memory register, and regenerated in their original locations every 7 microseconds. Each of these groups
of two locations, or the contents thereof, is called a "diad." Each diad begins with an "even" decimal address, and
ends with the next consecutive "odd" address (such as the diad with addresses 1134 to 1135). Diagrammatic
representations of portions of the HSM used throughout this manual are shown below.
The HSM address of each location is shown in the upper portion of the diagram, with the characters stored in
each location shown in the lower portion.
The primary purpose of the HSM is the storage of programs and data. These may be stored in any area of the
memory except for those locations reserved as Standard HSM Locations (see Appendix E).
THE BASIC INSTRUCTION
Each of the RCA 301 instructions consists of four parts:
1. Operation Code (one character)
2. N Character (one character)
3. A Address (four characters)
4. B Address (four characters)
An instruction, then, is made up of ten RCA 301 characters with the format:
III —. FUNCTIONAL DESCRIPTION