Val has an excellent post providing at length and even-handedly the facts on this topic. Like most liberal folk tales, the truth bears little resemblance to the mythology.
Update: Bernhardt Varenius at Anti-Socialist Tendencies has this post about Allende’s attempt to create a computer database to centrally manage the Chilean economy. What madness. This led me to flip through the chapters on socialist planning in Hayek’s best book Individualism and Economic Order. I thought I recalled a passage where he discusses how a central planner, even if he had every scrap of articulable knowledge that could be gathered, and even if he could digest it all in a timely fashion, would still be missing most of the essential knowledge which is required to carry on the daily business of life. I did not find a pithy one-liner, but I do recommend that you read those essays, written in the 1930s and not outdated one iota. In fact, the idiocy they rebut is still prescribed with a straight face routinely to this day.