On 10 Dec, 2008, at 05:53, cctalk-request at classiccmp.org wrote: An interesting question. I would have said they were common in the late 60s but not in the early 60s. None of the 1301s (built 1962-65) I have seen were on raised floors, maybe because 700 square feet of raised flooring would have been expensive, but I suppose not compared to 247,000 pounds for the computer itself. When I first started programming them in 1969, I think all the ones I visited were on raised floors, had 'tacky mats' and air conditioning, which often blew out of the floor. On the other hand, when I went to work for a company which made computers (in 1974) and which used them extensively for software development, there were no raised floors, no tacky mats and only one of the computer rooms had air conditioning because it was the only one to used exchangeable hard disks, the rest used paper tape or cartridge mag tape or one inch analogue tape for audio data which was used as test input to sonar processing computers. Just my experience, maybe not typical, and in the UK. Roger Holmes