1974 finally saw an attempt to move from the old DOS operating system to RSX. The old system basically allowed the machine to be used by one user with a second having minimal access. The new RSX operating system allowed two users to access the system in a sensible manner.
Quite a bit of software had to be modified to perform the transition and quite a bit of 1974 was spent in debugging the software. With the arrival of the new FR80 microfilm recorder, it was eventually decided that this should take priority and work on installing RSX was shelved until some time in the future.
The core of the FR80 was a III15 which was Information International Inc's carbon copy of the PDP15 so the people with expertise on the PDP15 moved over to the FR80. Quite a lot of PDP15 time was spent developing software for the FR80. Once the FR80 was in service, more time was available for development using the PDP15. Also, the systems developed for the SC4020 such as graphics previewers were redeveloped for the FR80.
A fuller description of the activities that took place on the PDP15 are given in the Quarterly Progress Reports of the Graphics Section and Basic Software Group.
A case was successfully made to the Atlas Computer Committee for the purchase of a fast interface for the PDP15.
This paper asks the Committee to approve the purchase of a DECWRITER teletype and a DEC LT19 interface for the Laboratory's PDP15 computer. The total cost should not exceed £2,000, including VAT.
Provision for these items has been made in the Estimates for 1975/76. However, they can be installed and paid for in the current financial year if this proves more convenient to SRC.
A pre-release version of RSX, the multi-program operating system, has been available to the Laboratory for a few months. This was requested in paper ACC 72/3. With modifications that the Laboratory is making, two people will be able to access the machine simultaneously when the official version is released, with the possibility of more if the processes are well-defined.
The main use of the system is graphics and two terminals are currently in use. One of these, a Tektronix 4010 storage tube, can be accessed through RSX by a user, who does not require the full responsiveness of the VT15 refreshed display, while the latter is being used. However, at the moment, the Tektronix is connected on a slow line (11O bits per second) and, although graphics is possible and some simple software for it has been written, it is not feasible for a moderately complicated picture. Purchasing a modified LT19 interface will upgrade this speed to 2400 bits per second and make graphics viable. Tektronix will also double as the second user terminal.
The cost of the LT19 interface is £529. It will also be necessary to add a clock at a cost of £90. Delivery and installation is £76. All prices include VAT. It is relevant to mention that the price of the LT19 is not dependent on line speed.
The main terminal on the PDP15 is a Teletype KSR35, modified by DEC, running at 110 bits per second. This device is not very reliable and, since it is a slow-speed terminal and the PDP15 has no lineprinter, other methods have to be adopted to obtain software listings. DEC manufacture a better terminal, a DECWRITER, which runs at 300 bits per second and is a modern, reliable device. Replacing the KSR35 would enable listings to be obtained at the PDP15 and, as this terminal is also one of the user terminals under RSX, the extra speed will be of benefit there.
The KSR35 could remain as an active spare (the system goes down completely if the master terminal is unavailable) or could be converted to a V24 interface and used in an office to the 1906A.
The DECWRITER costs £1,175, including delivery, installation and VAT.
