Multiplication

• Multiply two 32-bit numbers to obtain a 64-bit result that is spread between an even-odd pair of registers

• RX Format: label M R,D(X,B)

  • R is an even numbered register representing an even-odd pair of registers. The number to multiply must be in the odd numbered register

  • D(X,B) is the address of a fullword number to multiply by

• RR Format: label MR R₁,R₂

  • R₁ is an even numbered register representing an even-odd pair of registers. The number to multiply must be in the odd numbered register

  • R₂ is the number of a register containing the number to multiply by

Example 1:  M  4,TWO    where  TWO  DC  F'2'

BEFORE:    R4 = 05002037    R5 = FFFFFFFD  (-3 in decimal)

AFTER:     R4 = FFFFFFFF    R5 = FFFFFFFA
            64 bit representation of -6 

Example 2:  MR  2,1

BEFORE:    R1 = 00000004    R2 = 0000FFFF    R3 = 00000005

AFTER:     R1 = 00000004    R2 = 00000000    R3 = 00000014
                             64 bit representation of 20 

Example 3: MR  2,3  =>  squares the value in register 3

Division

• Divide a 64-bit number that is stored between an even-odd pair of registers by a 32-bit number.

• Results in a 32-bit quotient stored in the odd register and a 32-bit remainder stored in the even register.

• The remainder will ALWAYS have the same sign as the number being divided

• Could cause a S0C9 - Fixed Point Divide Exception, which is usually caused by division by 0

• RX Format: label D R,D(X,B)

  • R is an even numbered register representing an even-odd pair of registers. The dividend (ie. the number to be divided) must be spread between the two registers

  • D(X,B) is the address of a fullword number to divide by (ie. the divisor)

• RR Format: label DR R₁,R₂

  • R₁ is an even numbered register representing an even-odd pair of registers. The dividend (ie. the number to be divided) must be spread between the two registers

  • R₂ is the number of a register containing the number to divide by (ie. the divisor)

EXAMPLE 1: DR   2,8

Before:    R2 = 00000000    R3 = 00000007    R8 = FFFFFFFE  (-2 in decimal)

After:     R2 = 00000001    R3 = FFFFFFFD    R8 = FFFFFFFE
             REMAINDER        QUOTIENT
                          (-3 in decimal)

EXAMPLE 2: D    4,=F‘2’

Before:    R4 = 00000A00    R5 = 00000007

After:     Error (SOC 9) because the quotient will not be 32 bits



To get the desired results:

M   4,=F‘1’   to zero out the even register
D   4,=F‘2’

After:     R4 = 00000001    R5 = 00000003