I could tell you a story about an 11/780 at Fort Monmouth that ran without air conditioning and with the windows upen for 3 months. Serious intermittant problems sprung up. The humidity had rust on the TU45 tape drive motors. The problem isn't heat -- it's the rate of change. You get serious expansion cracks in the boards when the etches expand and contract. The faster the rate of change in temporature when running (both up and down) the worse the issue. The machine was flaky as hell. The thing would crash VAX/VMS about 5 times daily. I actually would boot the machine and hit each one with my little brass hammer. If it crashed... the board was replaced. Swapped about 6 boards in the data path and cache sections and the box was then stable for over three years. The 11/34's a lot lower in power draw and slower. It's probably less sensitive with some larger etches. I'd worry more about the peripherals. Disk drives with rusty parts in them are probably a bad thing. I know the tape drives would have a problem. The RL02's might even have a different flying height depending upon the temperature which could end in head crashes. If you kept the internal temp under 100 degrees you're probably ok... but if the outside temp's above 100... The real trick is to keep the temp as steady as possible. Perhaps strategic fan placement to keep it from getting too hot in certain places. Bill -- d|i|g|i|t|a|l had it THEN. Don't you wish you could still buy it now! pechter-at-gmail.com