On 6 Jul, 2007, at 18:07, cctalk-request at classiccmp.org wrote: Whilst working on my 1301, I was chatting to a friend who was an ICT/ ICL field engineer and later manager into the Fujitsu years. I told him that all copies of 1900 executive have been lost and he said that he might have a copy tucked away but that, if he had it at all it was on 7 track tape and we don't have a deck to read it, but maybe someone somewhere has a way of reading a tape which has not been touched for many years. I will let you know if he finds it, but don't hold your breath, like me he has a lot of buildings and does not go in some of them for long periods. With the 1301 we have a copy of 'Initial Orders' on the drum, a numeric dump of a slightly different version from another machine and also (dyleine?) copies of the original manuscript. Its only two drum bands (so less than 800 instructions), but it is the nearest thing to an operating system that the 1301 had. The 1302 Exec has not survived, nor even details of all the extra instructions in the machine, we know everything about a few, sketchy details from sales literature for others and there are probably a few we know nothing about. A recent documentary series "The Trap, What Happened to Our Dreams of Freedom" had clips of old footage, and in one there was a chap with a book open at a page showing what I immediately recognised as a 1300 instruction summary, the only coloured page in the 1300 programming manual. On freeze framing it and comparing with the 1300/1301 version, I see the arrangement is quite a bit different, and I think it must be a 1302 manual, but of course the image resolution, even on the original 16mm film would probably not allow it to be read, and certainly not off the video now on YouTube. Well, when and if he finds it, maybe what's written on the spool will give us a clue to if its any use or not. We've had some weird ones with Flossie too. We found a fault three weeks ago, all the read-modify-write instructions were randomly causing a subsequent instruction to fail, about once a minute. This is just long enough to get from the console to the oscilloscope, so you start a program and it seems like the machine is being a bitch and waiting for you to NEARLY get to find out what is wrong, but not quite letting you do it. At the heart of the machine is a shift register which is supposed to have exactly one '1' in it at all times. The duration of the instruction is controlled by how far along the register the '1' gets. With two of us working on the fault, I was probing various signals and eventually we traced the fault to the shift register when my friend shouted over that the fault had seemed to have disappeared. I found that the impedence/resistance of the scope probe on one of 25 pins on one of 4000 cards seemed to make the fault disappear (and reappear when removed). We think we were getting two '1's in the shift register, but anyway, we changed that PCB and all has been well since. Roger.