Control Data Cyber 170 State Hardware Reference Manual page 146

PP Arithmetic Instructions
Arithmetic Subtract
17d Subtract d
SBN d
This instruction subtracts d (treated as a 6-bit positive quantity) from the
content of the A register.
32d Subtract (d)
SBD d
This instruction subtracts the content at location d (treated as a 12-bit
positive quantity) from the A register.
42d Subtract ( (dl )
SBX
d
This instruction subtracts from the A register a 12-bit operand (treated as
a
positive quantity) obtained by indirect addressing. Location d is read from
PPM, and the word read is used as the operand address.
52dm Subtract (m
+
( d ) ) SBM m,d
This instruction subtracts the 12-bit operand (treated as a positive quantity)
read by indexed direct addressing from the A register.
In indexed direct addressing, the quantity m, which is read from PPM location P
plus 1, serves as the base operand address to which the content of d is added.
If d equals 0, the operand address is m, but if d is not equal to 0, m plus the
content in d is the operand address.
Therefore, location d may be used as an
index quantity to modify operand addresses.