Without losing anything else in the already-full rack, I'd need to route that cable between two racks. It's already tricky to roll the cabinets back into place without rolling over the existing round snakes between the cabinets, and I figure that wide ribbon cables would be more cumbersome (or is the BC11A round?). I have the system in a tiny room where it's not practical to have space behind the racks to get rear access without rolling them. -- Mark J. Blair, NF6X <nf6x at nf6x.net> http://www.nf6x.net/

Nothing electtically... The problem is that the 11/730 mouting box (BA11-Z??) is a bit odd. The boards go in from the left. Cables end up going downwards (either straight down or over the top of the card cage, then down between the backplane and PSU). Then into a removeable tray on the bottom of the mouting box, round a flexible plastic sheet and to another tray fixed in the rack. The idea is to make the cables route nicely when yout slide the box in and out (something you have to do on the 11/730 to change the microcode tape or get to the main circuit breaker). I am not sure how a BC11A cable would like being folded back and forth like that. The official way was, I think a board in the Unibus out slot of the 11/730 that had 3 40 pin Berg headers on it. This took 3 normal 40 way ribbon cables which went round the cable routing thing and to a similar board in the Unibus in slot of the expansion box. I think there were even bulkhead panels to route the cables to another rack cabinet. I have the boards and cabling somewhere... My 11/730, which is a 'to be started soon' project has 4M of RAM and thus 2 spare hex height slots. One contains a DMF32, the other a TSU05 tape controller. I have a half-rack to put it all in. Obviously I am putting the CPU and R80 drive in that rack, the question is what else. I think an RL02 is pointless (the Integrated disk controller in the CPU of an 11/730 will talk to up to 4 drives. One can be a R80, the others are RL02s). The obvious thing is a TS05 (Cipher F880) tape drive, I have one but with a wrecked door so it needs repairs. I wonder if a Unibus expansion box would be more use though. Incidentally : It appears the DECSA (ethernet comms server) PSU is the same PSU as that in the 11/730 with the memory PSU board left out. The schematics are in the 11/730 printset, they are not in the DECSA printset. Similarly the LA100 printset doesn't include the PSU schematic, the LA210 one does, and it's the same unit again. Totally useless coincidence that I noticed while doing a cryptic crossword : 'ethernet' is an anagram of 'three ten', and the original ethernet speeds were three and then ten megabits/second. -tony

That's a much better description of the 730's mechanical peculiarities than I came up with. I was more concerned with cable management between the two racks, since I have them in a tiny room where I need to roll them around to get access to the back (it's literally a tiny bedroom in a manufactured home... basically a doublewide trailer that's been fastened to a foundation after having the axles and drawbar cut off!). It's already tricky to roll the racks back into place without running over the power cables, tape drive cables, serial lines and power controller cable. But managing the cables in the cable tray area is another thing that needs to be done right. Three narrower cables sound like they would be easier to manage than one wide one. Based on the hardware user's guide that I have (and which I do plan to scan and share), I gather that UNIBUS expansion cabinets would generally be used in a configuration that's in a larger rack and has both TU58 slots on the front panel. I haven't seen one of those in person before. My system is the configuration that's in one or two short racks. The main one is completely filled by the RL02, VAX-11/730 and R80 drives, from top to bottom. The other rack contains the optional TU80, with an unused bay below it. I haven't measured the size of that unused bay yet, but it looks like it may be tall enough for a UNIBUS chassis. Maybe I could adapt one of my empty PDP-11/44 chassis boxes for use as an expansion chassis? Or another possible use for that slot could be for my Kennedy 9610 tape drive. The TU80 looks like it probably has a Pertec interface, so I should be able to add the Kennedy drive to the chain to get more BPI options in the system. Now that I have a computer with a Pertec interface running, buying/building a Pertec adapter for my Mac or Sun doesn't seem so important. Assuming I can bring up networking on the VAX that is, and that I can figure out how to do block-level stuff under VMS. -- Mark J. Blair, NF6X <nf6x at nf6x.net> http://www.nf6x.net/

Sorry to hear that it's been decabled. Take your time to route those cables through the bottom pan properly, and based on my experience so far, I do not recommend trying to route anything but flat cables through the pan area. Route anything round up over the top and along the folding support arm (what I've been calling a "gantry", but not necessarily correctly). For anything temporary, might as well leave the cabinet slid out and let the cable dangle. The 730 is nicely made for sliding in and out easily, but really not optimized for frequent hardware configuration changes. Yup, you're exactly right about that. That makes sense to me, particularly if you will not be constrained by the original rack configuration like I am. The 730 has limited UNIBUS slots anyway, so might as well use an expansion rack for anything you might change frequently. -- Mark J. Blair, NF6X <nf6x at nf6x.net> http://www.nf6x.net/

In mine, an RL02 drive is the third unit of the rack containing the CPU cabinet, and the TU80 tape drive is too tall for that slot (though one of the later front-loaders would probably fit). If you don't need an RL02 drive, then i think the hole it would leave behind is just the right size for an expansion chassis. Hmm, if it's the same rack that originally had the RL02 in it, then there should be no top panel, as the top-mounted RL02 was meant to be opened without sliding it out. With an expansion chassis in its place, you should be able to get full top access to the expansion chassis without sliding anything in or out. That seems like it would be super awesome since you want easy access for swapping cards. And no need to run a BC11A cable between racks, either. I've played with the idea of making a top cover for my main rack that rests on the cabinet sides, straddling the RL02. If I unscrew the shipping bracket at the back of the RL02 then I could slide it out for pack changes, and leave other stuff like a terminal sitting on top. I usually seem to have stuff sitting on top of the RL02 and/or TU80 anyway, and then I need to shuffle the stuff around whenever I need to open one or the other. Ok, that's enough enthusiastic agreement for now. Off to the other thread for some more enthusiastic disagreement! :) -- Mark J. Blair, NF6X <nf6x at nf6x.net> http://www.nf6x.net/

Aha! I didn't know that. Makes a lot of sense, and takes up half the floor space compared to having a TU80 in a second rack. I think the documentation I have predates that configuration option. If you do have it, I wonder if it would be hard to add hinges for easy access to a top expansion chassis? -- Mark J. Blair, NF6X <nf6x at nf6x.net> http://www.nf6x.net/

On Tue, Jun 16, 2015 at 12:20 AM, tony duell <ard at p850ug1.demon.co.uk> wrote: The VAX-11/730 System Installation Guide (EK-SI730-IN-003) has information about how to load the catch pan. Given all the 90 degree and 45 degree folds, it's the sort of thing you only want to do to a fresh cable once. There might also be a specific 11/730-Z detailed installation manual. I have a memory of one but don't know the part number. My memories of those days (we had two 11/730s) is that if you don't do it the way they did, either things won't reach (or be on the wrong side to fit into bulkhead connectors) or you'll have to redo it. https://archive.org/details/bitsavers_decvax730E83_4699164 We did have that. It was nearly essential. We had the CPU, memory, and the default (as shipped) peripherals. Everything else went into our BA-11K FWIW, we only had the RB80/RL02 version. Tape was a TU80 with the controller in the BA-11K. Our COMBOARDs also went in the BA-11K, but that was also for our convenience of swapping out our own product for testing and firmware swaps, etc. -ethan

An expansion without a reapeater would work just fine electrically. I'm curious about whether some sort of repeater exists that uses a thin, round cable for an application where it's desirable to be able to move the expansion around easily. And also where it's cheap and easy to replace the cable after rolling a rack cabinet over it one time too many! :) -- Mark J. Blair, NF6X <nf6x at nf6x.net> http://www.nf6x.net/

Interesting! Thanks for sharing! I could probably make one "cheaper", but I couldn't make one "cheap". :) Another approach would be to build a BC11A-equivalent cable using multiple narrower ribbon cables (as previously mentioned in this thread), and use the round-jacketed-shielded ribbon cable. The stuff isn't cheap, though, and a couple of round-jacketed 40-conductor cables probably aren't any more flexible than the Pertec tape drive cables I already have snaking about between the racks. -- Mark J. Blair, NF6X <nf6x at nf6x.net> http://www.nf6x.net/