Problems With Data Dependencies
Executing instructions in parallel (i.e. simultaneously) raises problems with data dependencies, meaning that some instructions may be dependent on the results of others, and hence care must be taken to execute in the correct order.
Take for example these sequence of instructions:
r1 = r2 + r3
r7 = r1 + r4
We have a RAW (Read After Write) data dependency here, meaning that we must wait for instruction 1 to finish before executing instruction 2, as we require the correct value of r1 (register 1). Hence these instruction cannot be executed simultaneously.
Read more about this topic: Shelving Buffer
Famous quotes containing the words problems and/or data:
“I have said many times, and it is literally true, that there is absolutely nothing that could keep me in business, if my job were simply business to me. The human problems which I deal with every day—concerning employees as well as customers—are the problems that fascinate me, that seem important to me.”
—Hortense Odlum (1892–?)
“To write it, it took three months; to conceive it three minutes; to collect the data in it—all my life.”
—F. Scott Fitzgerald (1896–1940)