quadra marginal video we are having a problem with a quadra that has stumped a couple of techs sent to us by the vendor as well as us this quadra is stuffed with mb ram mb vram and some large disk mb i think what happens is that after a certain variable interval of time the video circuitry loses vertical sync it is quite apparent that the mac cpu is still ok and the problem really seems to lie with the video circuitry since you can still save your documents quit your aplpications even pull down menus etc only the display is scrolling lik crazy so it s pretty hard to hit menu items we had the original logic board replaced twice now and the same problem has been occurring on all boards although the inteval between occurrences has varied the first board had this problem every about hr more often if the cache was turned off yes off this is the only symptom that is not obviously related to the video circuitry after all the cache is on the cpu right the second board had the problem every about minutes we did not keep it rather we put the original back the current board we have has this problem a lot less often has gone about a week without doing it but did it twice within an hour yesterday the technicians that have come out to try to figure it out seemed pretty sharp and tried a number of sensible things most of which we had previously tried ourselves anyway these included swapping the ram swapping the vram swapping monitors different apple rgb and apple rgb swapping cables disconnecting hd and booting from floppy sacrificing various small mammals here are some other facts when we put a rasterops procolor on the nubus the problem is fixed it does not occur with the internal video or the procolor video out the vendor cannot reproduce the problem back in their shop on the boards that exhibit it in our lab apple is said to be getting a little bit pissed off at shipping us boards that they cannot find anything wrong with and getting them shipped back as faulty according to us here are some speculations i bet that neither apple nor the vendor has tested these boards with that much ram and vram on them simultaneaously which may have something to do with their finding it hard to reproduce the problem though we can reproduce it with just mb of ram so this is probably a red herring the vendor s representative blames metal in your walls claims that our walls have metal in them which interferes with the mac s operation we have another in the lab which works like a charm though it s not in the exact same spot please don t tell me this is probably it i do not want to believe it it s probably not poltergeists since they do not have badges to get past security at the entrance to our site has anyone any ideas please please email as well as posting cause i seem to be spending a lot of time rebooting my mac lately and have a lot less time available to read news thank you in advance carlo tiana nasa ames research center carlo vision arc nasa gov carlo cvs rochester edu carlo white stanford edu we always remember you have a choice carlo vision arc nasa gov
