tag:blogger.com,1999:blog-8108350772243606631.post1900009460044184251..comments2022-07-03T14:32:48.624-04:00Comments on Fornax Chimiæ: System ReadyMichael L. Umbrichthttp://www.blogger.com/profile/11491979686972851070noreply@blogger.comBlogger2125tag:blogger.com,1999:blog-8108350772243606631.post-73979455858520722192014-07-26T09:42:44.996-04:002014-07-26T09:42:44.996-04:00We typically have a work session about once per we...We typically have a work session about once per week where we power (parts of) the system up for around 8 hours at a time. So, we're not cycling the power every day. Each subsystem has a DC inhibit so we can selectively power on only what we are working on. We haven't done any work on the disks yet, and so those have been left off most of the time since the system arrived. We are installing a newer SCSI array to use in place of the stock drives. We only plan on using the original drives to recover software and to benchmark performance.<br /><br />At http://rcsri.org we've been restoring and running early machines for 20 years now and some of our members worked on these machines as field service techs for years before that when the machines were new. We're cautious about how we operate these historic systems. Even for machines from the early 1970s the majority of failures that we've seen are things like power supply capacitors drying out and tape drive capstans physically degrading. In theory you might expect solder joints to fail but in practice we only occasionally see intermittent failures from expansion causing cards with edge connectors to become slightly unseated.<br /><br />For the Cray there is a large amount of thermal mass in the backplane and also in each of the modules. The cooling system is very effective and after powering the system down the components are barely warm to the touch. We've been collaborating with our colleagues at http://www.cray-cyber.org who have similarly restored systems and they have not reported any problems of the kind that you describe.Michael L. Umbrichthttps://www.blogger.com/profile/11491979686972851070noreply@blogger.comtag:blogger.com,1999:blog-8108350772243606631.post-36129801942086280382014-07-26T04:52:09.945-04:002014-07-26T04:52:09.945-04:00You mention that you forget to then the batteries ...You mention that you forget to then the batteries off when you "are done for the day"; this implies you may be power cycling the machine daily--something they were not designed for, as a power cycle means a thermal cycle and a thermal cycle includes expansion and contraction of components which result in solder fatigue. Mechanical cycles are also hard on these old SCSI and IPI disks.David Michaudhttps://www.blogger.com/profile/04725105670033642642noreply@blogger.com