ALU当然是处理器内核的一个重要单元，我们来看图说话：
再来一张放大图：
ALU的全称是Arithmetic Logic Unit！中文是不是应该叫算术逻辑单元？还是来英文吧。
Two 40-bit ALUs operating on 16-bit, 32-bit, and 40-bit input operands and output 16-bit, 32-bit, and 40-bit results.
Functions
- Fixed-point addition and subtraction
- Addition and subtraction of immediate values
- Accumulator and subtraction of multiplier results
- Logical AND, OR, NOT, XOR, bitwise_XOR, Negate
- Functions: ABS, MAX, MIN, Round, division primitives
- Supports conditional instructions
Four 8-bit video ALUs ：Explained in more detail as part of Advanced Instructions section
ALU Operations ：Conditional Code (CC) Bit in ASTAT
CC bit is used in several instructions
- Action taken in the instruction depends on the value of CC
- If cc jump here; //if cc = 1, jump to label “here”
- If cc r3 = r0; // perform move if cc=1
CC bit value is based on a comparison of two registers, pointers or accumulators；CC bit can be moved to and from a data register or ASTAT bit；CC bit can be negated；
下一篇就准备简单说一下MAC，全称：MULTIPLY-ACCUMULATORS |
