Improvements
The instruction set of the i486 is very similar to its predecessor, the Intel 80386, with the addition of only a few extra instructions, such as CMPXCHG which executes the compare-and-swap atomic operation and the XADD which executes the fetch-and-add atomic operation returning the original value, unlike the ADD instruction that only returned some flags.
From a performance point of view, the architecture of the i486 is a vast improvement over the 80386. It has an on-chip unified instruction and data cache, an on-chip floating-point unit (FPU), except in the SX and SL models, and an enhanced bus interface unit. Simple instructions (such as ALU reg, reg) execute in one clock cycle. These improvements yield a rough doubling in ALU performance over the 386 at the same clock rate. A 16-MHz 486 therefore has a performance similar to a 33-MHz 386, and the older design has to reach 50 MHz to be comparable with a 25-MHz 486 part.
Read more about this topic: Intel 80486
Famous quotes containing the word improvements:
“A country whose buildings are of wood, can never increase in its improvements to any considerable degree.... Whereas when buildings are of durable materials, every new edifice is an actual and permanent acquisition to the state, adding to its value as well as to its ornament.”
—Thomas Jefferson (1743–1826)
“The improvements of ages have had but little influence on the essential laws of man’s existence: as our skeletons, probably, are not to be distinguished from those of our ancestors.”
—Henry David Thoreau (1817–1862)
“... these great improvements of modern times are blessings or curses on us, just in the same ratio as the mental, moral, and religious rule over the animal; or the animal propensities of our nature predominate over the intellectual and moral. The spider elaborates poison from the same flower, in which the bee finds materials out of which she manufactures honey.”
—Harriot K. Hunt (1805–1875)