Setting up a VAXstation

OK, a higher-level description would be 'something that records a number of digitla signals and displays their relative timing'. The sorts of things you might use one for would be to trace machine code (or microcode!) instructions/addresses on a processor bus (but cache memory and even a pre-fetch buffer makes that a little hard!), checking things like handshake sequencies on an interface, recording bit-seiral signals so you can decode them later, checking state machine sequences, and so on. What it is _not_ is a majic box that finds all digital electronic faults. It's a tool, which if used intellegently will help, though. You mean oyu've not been on the receiving end of my flames about this :-). Suffice it to say I've just written a presentation where I describe that as a 'ridiculous method'. I tried it twice when I was young-and-foolish and both times it not only didn't find the fualt, it actually left me more confused. I ended up tracing the fault using test gear in the traditional way, and it took me a lot less time. The main prolems are : 1) You have to know the module you're swapping in works. This is not always certain, particulalry on classic machines. Whre would you find known-good boards for an obcure 30-year-old system? 2) E very careful if the old and new boards are not the same revision. This caught me once, I swapped in what I thought was the same board (same part number, etc), only to find (after _much_ testing) it was a later version that needed a backplane modification to work. 3) A fault elsewhere in the machine could have damaged the origianl board, and might damage the replacemetn too. An obvious example of this is a defective power supply that's damaging chips on the logic boards 4) Even if you replace a board and the machine works, you may not have found the fault. One example of this (which happened to me) can be simiplified into a system of 2 modules linked by some interface. Let's call them 'A' and 'B'. You replace 'A' and the machine works. Unfortunately, the old 'A' was working fine _and was withing tolerance for things like interface timing (but towards the edge of that tolerance_, module 'B' was failing and couldn't handle the timing of the old 'A'. The new 'A' was on the other side of that tolerance, so it worked with the fialing 'B', but in time 'B' got worse and worse and the machine failed again. Things were even more different before that IMHO. In many of my machines (and those of others on the list), theres isn't a processor chip. The processor is several boards of fairly simple chips -- simple gates, flip-flops maybe some small RAMs or PROMs. I actually wonder how you can be 'competent with hardware' and 'know bugger-all about electronics' To me those are contradictory statements. We also ssem to have different attidudes about learning new things. I tend to spend the time to learn whatever I need to fix the problem. I don't claim to be a programmer, I;d never write an OS or a compiler or an emulator, or.. from scratch. But when I had a problem which was clearly due to a device driver not correctly hadnling the somewhat odd hardwre in my PC, I learnt enough C to understand how said driver worked, and then editied the sources to get it to work. Actually, there are some ISA boards I am still looking for. Top of the list is an origianl IB< PGC. I don't suppose your Apple bits include Laserwriter spares, do they? I am looking for partially-dead boards to raid for custom chips (PALs, microcontrollers, etc) -tony