Cray CRAY-1 - CRAY-1 Instruction Formats

INSTRUCTIONS
INSTRUCTION FORMAT
Each instruction is either a one-parcel (16-bit) instruction'or a t~/O
parcel (32-bit) instruction. Instructions are packed four rarcels per
word. Parcels in a word are numbered from left to right as 0 through 3
and can be addressed in branch instructions. A two-parcel instruction
may begin in any parcel of a word and may span a word boundary. A two-
parcel instruction that begins in the fourth parcel of a word ends in
the
first parcel of the next word. No padding to word boundaries is
required.
Instructions
have the following general form:
g h i j k m
~First parcel~Second parcel~
Figure 4-1. General format for instructions
Five variants of
this general format use the fields in different ways.
T~!o of these vari ant forms are two-parcel formats, two are one-parcel
formats,
and one is either a one-parcel or a two-parcel format.
ARITHMETIC, LOGICAL FORMAT
For arithmetic and logical instructions, a 7-bit operation code (gh) is
followed by three 3-bit address fields. The first field, i, designates
the
result register. The j and k fields designate the two operand
registers or are combined to designate a 6-bit B or T register address.
This format
is illustrated in figure 4-2.
2240004
4-1
E
4