How to get the clock accuracy in one thousandth of a second

Typedef struct _ binint32

{

_ Int32 i32 [2];

} Bigint32;

Typedef struct _ bigint64

{

_ Int64 i64;

} Bigint64;

Typedef union _ bigint

{Bigint32 int32val;

Bigint64 int64val;

} Bigint;
The following code obtains the high and low clock counters from the operating system. Fill in two 32-bit sections of _ int64 data respectively:

Bigint start_ticks, end_ticks;

_ ASM {

Rdtsc

MoV start_ticks.int32val.i32 [0], eax

MoV start_ticks.int32val.i32 [4], EDX

}
 
Rdtsc (read time stamp counter) is an assembly instruction that loads the content of the timestamp counter into the eax and EDX registers. After the code is executed, start_ticks contains the complete clock count. Call the above Code again, replace start_ticks with end_ticks, and subtract start_ticks from end_ticks to get the clock cycle that passes during the two calls.