Peter Farr & the Ferranti Argus Computers

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In Peter's words ...

"In your picture, the green and red DIL packs each provide two DC isolated drivers, which is an NPN transistor with its base driven by a pulse transformer. The 16 red coloured DIL packs are C17804/29116 and are the Drive Transformer Packs (DTP) for the address lines of the core matrix. Each plane is organised as a 64 * 64 matrix, the FSA2500M you have described form the diode matrix which reduce the required drive lines down from 64 * 64 to a more manageable 8 * 8. Each of these 16 lines requires 2 drivers one to drive Positive when writing and the other to drive negative when reading.

The 4 Green coloured DIL packs are C17804/29116 and are the Inhibit Transformer Packs (ITP) for the inhibit lines of the core matrix, 1 being required for each of the 8 bit planes. As all 8 planes are driven by the same X and Y drivers, then to stop a 1 being written for a specific bit an appropriate inhibit pulse (opposite sense) is generated for an individual plane to cancel the XY driver selection pulse.

One of the big advantages of core store (which most people forget) is that it did not require power to 'remember' its content. So with correctly written software you could simply power the computer off and at a later date power it back on and continue where you left off.

Contrary to Andrew Graham's very brief description of the Argus 600, it was an 8-bit machine (13-bit address). It was never intended to be a continuation of the previous Argus range but to replace the hardwired sequence controllers which were used throughout industry at that time. The complete Argus 600 with power supplies (which occupied 40% of the space), Input output cards and core store (which occupied another 40% of the space) was only 19 x 23 x 10.5 inches (W x D x H). The actual processor was built on a single multilayer PCB (about 18 x 0.5 inches), and consisted of only 159 TTL logic DIL packs.

You mention about the IC legs being bent so they could be surface mounted. The Argus 600 was designed for field repair and the user manuals provide a complete technical description of the equipment and fault-finding details. If you were brave enough you could fault find and repair the computer yourself!

With a multi layer printer circuit board with plated through holes, the only safe way to remove a component is to cut all its legs, and then remove each leg individually. This surface mounting technique allowed an individual IC leg to be lifted for test purposes, or the whole component to be safely removed without damage to the board. The spares kit for the Argus 600 also include the appropriate temperature controlled soldering Iron.

There were two basic variants Argus 600 with a cycle time of 4.6 usec and the Argus 600-2 with a cycle time of 1 usec. The maximum amount of core store was 8192 bytes for program and data, though there was a later modification that allowed an additional 8192 bytes for data only to be fitted. The core store was addressed as 256 pages of 32 lines (8192).

The instruction set is beautifully simple and consisted of only 8 instructions that carried address information and 15 non-address instructions.

Each basic instruction consisted of a 3-bit instruction field and a 5-bit line field. The instructions are:

That is it, from those few instructions you can do anything! I first came across the Argus 600 when at grammar school around 1971, we had one in the Physics department and it was running Basic. For that era, it was almost the equivalent of the personal computer. Data input and output was through a Teletype with your program stored on paper tape. I would think it was about as powerful as the Sinclair ZX80, but without any graphics capability. Andrew is right in that the Argus 700 series is a very popular industrial computer and is still in use today. I know of one Argus 700 system that was decommissioned only a few years ago by one company, to be shipped immediately to another company and re-commissioned for a totally different task. I joined Ferranti as an apprentice in 1973 and spent the next 23 years happily programming Argus 500s, 600s and 700s for a variety of tasks. It was a great time when you were in total control of the computer, unlike today where there are Gigabytes of poorly written software that just get in your way and do their best to hold you back."

Peter Farr, November 2006