When I came into the DEC world I had to decide whether my employer should get a high end PDP-11 or a VAX. Decided that the VAX would be a better investment, since we were going to hook up custom hardware for data transfer from instruments and we would be writing programs to manage the data and do statistical analysis of very large volumes of it. When the big instrument started a scan and dumped volumes of data to the VAX, I assigned high software and hardware priorities so we wouldn't miss anything as it went by. Everything else stopped in its tracks for about a minute. We started with version 2.x of VMS and by version 4 DEC had fixed most of the places where it could be sluggish in response to the interrupts for data acquisition.
A few years later, another group at the same place talked management into buying them a VAX, but planned to use Unix. One of them came to me and asked me how to format a hard drive so they could load the operating system from tape. Sent them over to Rice U. where the could find people who enjoyed that sort of challenge. I had work to do, and didn't think the other group did a good job of planning the installation. Later after I left that job I worked a contract converting and enhancing software for the management of a gas pipeline system. We went from PDP-11 to a network of VAXes. At least the VAX assembler made a nominal distinction between an address and data of same length. We did most of the software in FORTRAN, but there were routines that used assembler for speed in handling real time data. We rewrote in FORTRAN some of the routines that had been in assembler on the PDP-11s. One problem with the PDP-11 was the need to bounce among operating systems, since RT-11 was needed for data acquisition handling. Choppy At 06:57 AM 6/1/03 -0500, Edmund Cramp wrote: >Prior to the VAX line, you could get quite acceptable performance out >of a PDP-11 running RSX11-M with 5-10 users and 256kB running on a >pair of removable 10Mb disks - of course this was using character >based terminals like VT-100's but you could do quite a lot of graphics >using vector based devices like the Tektronics 4006 etc... see >ftp.emgsrus.com/pictures/lab02.jpg for a picture of an 11/23 running a >real-time video data collection system (7 cameras) and 3 terminals.
