rayan@ai.toronto.edu (01/29/87)
We have 3 CDA array processors sitting on a VAX-11/780. I hope eventually to replace the VAX with Suns of some ilk. However, in order to do that, it is necessary to find some way to retain the functionality of the CDAs; we use them primarily as display devices. To do that, there are two possibilities: 1. Sell the CDAs and buy something VMEbus compatible. 2. Find a way of hooking the UNIBUS-only CDAs to a VMEbus. Item 1 is not likely to be practical without a large infusion of funds from somewhere... unless of course someone who reads this would like to buy them off of us. Comes with lots of cross-development tools. Of course, if somebody would give us a Grinnell or a Pixar, that would solve the problem. I digress... Item 2 is the object of this query. Since the CDA is a dumb device, and since hopefully the '780 will go away at some point, we are left with a bunch of relatively dumb cards sitting on a UNIBUS backplane, without a processor to keep them company. The problem is how to get them to talk to a Sun & vice-versa. We have looked into the following approaches: - Dig up a busconverter. The company that everyone seems to think is making VME-UNIBUS converters doesn't, and basically told us to not count on them for such an item. If you know of someone who makes one or is about to bring one into production, please let me know! - Dig up a UNIBUS-to-any-other-bus-that-there-is-a-VMEbus-converter-for. We know of no proven solution. If you do, please please let me know! Daisy-chaining bus converters is likely to be the cause of wonderful problems.... - Put a DR11W on the UNIBUS and use standard VMEbus--DR11W interface. This won't work without coding and burning new proms for the CDAs, since the DR11W is just as dumb a device as any other and needs a processor to make proper use of. Theoretically, the CDAs could be reprogrammed to poke it appropriately, but we don't want to do that. - Get an El-Cheapo PDP-11 to stick them onto. The change from the present environment (4.xBSD) on the VAX to the PDP would be just as traumatic as changing to a Sun. The OS would be eminently non-standard in our environment. This seems like a good idea for the hardware, but a bad idea for the software. - Get an El-Cheapo VAX-11 to stick them onto. Something like a '730 perhaps. We can run sane UNIX on it, and no tools need to be ported or changed. Is the best solution from a hardware/software point of view. The possible problem here is economics. How little are people willing to let their '730s go for? The market for these things isn't exactly overwhelming, so I would expect them to be quite cheap. All that is needed is a barebones system -- we can always add in some distributed file system if we need gobs of disk space. - Get a not-so-El-Cheapo microVAX-II to stick them onto, along with a Qbus-UNIBUS converter. Fine solution, except a bit too expensive unless we can get a used microvax for the same price as a '730... I gather that the Qbus-UNIBUS mapping in uVAX-I's isn't transparent, which seems to make them less desirable for the purpose. Is this correct? - Build a busconverter in-house. Not infeasible technically, but we have better things to do with people's time. If anyone has done this already, I'd like to hear. Questions: 1. There is this crazy idea of using a VMEbus-Qbus converter, and hook it to a Qbus to UNIBUS converter. Comments on the practicality of this idea? [ I can hear people fainting... ] I am not sure if the VMEbus-Qbus converter is transparent or uses (sigh) a DR11W interface. Anyone know? 2. Anybody know of a UNIBUS-to-any-other-bus converter that does NOT use a DR11W, and which might eventually be connected to a VMEbus? 3. If you have a 730 (or uVAX-II) taking up valuable rack space, what would you be willing to sell it for (I would just like an idea of what we would have to pay to get such an item, but if you want to more or less give one away now, I'm listening)? 4. Are the prospects of selling off the CDAs as bleak as we think? 5. Any other approaches we haven't thought about? One would think there is a large market for VME-UNIBUS converters. How come no one seems to be making one? If VME-Qbus converters exist, what is the big difference to explain the lack of UNIBUS ditto? Any and all help would be appreciated. rayan