The earliest PDP-8 model (informally known as a "Straight-8") used diode-transistor logic, packaged on flip chip cards, and was about the size of a refrigerator.
This was followed by the PDP-8/S, a desktop model. By using a one-bit serial ALU implementation, the PDP-8/S was smaller, less expensive, but vastly slower than the original PDP-8.
Intermediate systems (the PDP-8/I and /L, the PDP-8/E, /F, and /M, and the PDP-8/A) returned to a faster, fully-parallel implementation but used much less-expensive TTL MSI logic. Most surviving PDP-8s are from this era. The PDP-8/E is common, and well-regarded because so many types of I/O device were available for it. It was often configured as a general-purpose computer.
In 1975, early personal computers based on inexpensive microprocessors, such as the MITS Altair and later Apple II, began to dominate the market for small general purpose computers.
The last commercial PDP-8 models in 1979 were called "CMOS-8s" and used custom CMOS microprocessors. They were not priced competitively, and the offering failed. The IBM PCs in 1981 cemented the doom of the CMOS-8s by making a legitimate, well-supported small microprocessor computer.
Intersil sold the integrated circuits commercially through 1982 as the IM6100 family. The IM6100 was a straight-8 CPU. An IM6101 programmable interface element was a basic PDP-8 I/O port. The IM6103 memory extension, DMA and interval timer converted an IM6100 into something resembling a PDP-8/E's CPU. The IM6103 parallel I/O, and IM6402 UART were basic PDP-8 I/O devices on an IC. Intersil also offered compatible sizes of RAM and ROM. Although this family of ICs had less logic than many competitors, and could have had smaller silicon and therefore undersold competitors, it used CMOS, then a larger technology, and failed." (Wikipedia)
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DEC PDP-8 - Various - [BIN] (TOSEC-v2006-04-25)
DEC PDP-8 - Various - [PTP] (TOSEC-v2006-04-25)
DEC PDP-8 - Various - [RK5] (TOSEC-v2006-04-25)
DEC PDP-8 - Various - [RX1] (TOSEC-v2006-04-25)
DEC PDP-8 - Various - [TU6] (TOSEC-v2006-04-25)