TLF Advert - September 1977

One of the most popular range of minicomputers in the 1970s was DEC's PDP - Programmed Data Processor - series of sometimes room-sized machines (once disk units and printers had been added).

The first of these to be commercially successful was the PDP-8, a 12-bit minicomputer which was first launched in 1965 and which sold over 50,000 units.

Unfortunately for DEC, these machines, whilst popular, were also very simple, being built from various forms of transistor logic rather than the integrated circuits of later computers.

According to some sources, this made the PDP-8 - with its large software library - susceptible to cloners^[1], long before Apple and IBM would suffer the fate with their Apple II and 5150 models respectively.

This machine from TLF of Littleton, Colorado, appears to be one such clone as it claims PDP-8E compatibility, possibly as it was likely built around Intersil's 12-bit 6100 "CMOS-PDP8" - a chip version of the transitor-based original, but which was obviously much smaller and which consumed much less power.

This made it suitable for sticking in a mini desktop box, nicely showing the progression of miniaturisation - of what is functionally identical to the refrigerator-sized PDP-8 - over the preceding decade.

TLF wasn't alone in offering compatibility with PDP minis, as the contemporary Heathkit H11 was doing the same thing with the PDP-11 - although in that case it was definitely in agreement with DEC, as the machine was produced as a partnership.

The Mini 12, which came with 8K of memory, an operating system, a serial interface and a controller for no fewer than eight digital tape drives, arrived fully assembled and debugged.

It retailed for $895, or about £5,200 in 2024. The first PDP-8 cost $18,500 when released in 1965^[2], which is around £300,200 now.

That was considered relatively cheap at the time, but the Mini 12 is nearly 60 times cheaper in real terms.

The PDP-8/E, which was still in production up until 1978, was a more modest $6,500^[3] - that's still over seven times more expensive.