Clock for CLD and LODSB in TASM - Programmers Heaven

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Clock for CLD and LODSB in TASM

nklnkl Posts: 14Member
Could somebody tell me what is the purpose of clock in CLD and LODSB? The clock in CLD is 2, while the clock in LODSB is 12. May i know what steps, i should care if i write a program which having this two terms? How is the clock will affect CLD and LODSB?

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  • AsmGuru62AsmGuru62 Posts: 6,519Member
    : Could somebody tell me what is the purpose of clock in CLD and LODSB? The clock in CLD is 2, while the clock in LODSB is 12. May i know what steps, i should care if i write a program which having this two terms? How is the clock will affect CLD and LODSB?
    :
    [blue]The clock is a time for CPU to execute that instruction. LODSB is (read: WAS) 6 times longer than CLD. Of course, these numbers are for very old CPUs. The CPU today are much faster, so CLD may be 1 clock and LODSB may be 2 clocks. Interesting, that latest Intel manuals do not have the CLOCK field anymore - maybe all instructions are timed at a single clock?

    Simply write your code and do not count clocks. When code works - THEN start optimizing. There are few optimization techniques possible. Making your code and data properly aligned and making instructions shorter. Example:

    'xor ax, ax' is better than 'mov ax, 0'

    or

    or ax, ax
    jz AX_IS_ZERO

    is better than

    cmp ax, 0
    je AX_IS_ZERO

    or

    L1:
    ...
    LOOP L1

    is slower than

    L1:
    ...
    DEC DX
    JNZ L1

    and so on... - read the Intel manuals on optimization. Of course, the most speed up in the correct data layout and good algorithms, so design your project BEFORE actual coding.

    [/blue]
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