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A B series FLIP CHIP used in a KA10

FLIP CHIP was DEC's trade name (a registered trademark for DEC) for a lengthy series of small cards used to build computers, and devices for them. It was a successor to DEC's earlier System Modules. The earliest FLIP CHIPs performed generic, simple functions, similar to an integrated circuit.

(They should not be confused with the generic technology term 'flip chip'; the DEC version, properly spelled with all capital letters, as in the trademark filing, got its name from the fact that some early FLIP CHIPs used flip chips. The latter was a component mounting technique which quite rapidly faded. The name was retained although the majority of FLIP CHIPs never were flip chip-mounted, as it became apparent that the flip chip mounting technique was highly un-reliable.)

FLIP CHIPs were used in the DEC PDP-7 (referred to in documentation as the "FLIP CHIP"), PDP-8, PDP-9 and PDP-10, beginning on August 24, 1964.

They were introduced as a cost-reduction measure; a FLIP CHIP plugged directly into a 144-pin connector block backplane with wire-wrap pins on the back side; automatic Gardner-Denver wire-wrapping equipment could wire the connector blocks to produce larger functional modules.

Early FLIP CHIP modules were single-height, normal-length modules, approximately 4 inches long and 2.5 inches wide. These had 18 contact fingers on one side of the PCB only (the so-called 'solder' side); the contact pads were 'numbered' from the DEC Alphabet.

The earliest FLIP CHIPs, introduced in 1964, used discrete transistors. FLIP CHIPs incorporating IC technology soon followed, and the limited number of contact pins eventually became a problem, so that eventually contact fingers were added on the other ('component') side as well, for a total of 36 connectors, 18 on each side.

DEC continued to use the name up into the period when extended-length quad-height cards started to appear, e.g. in the KA11 CPU. However, although these special-purpose cards are labelled 'FLIP CHIP's, they are generally not considered to be 'true' FLIP CHIPS; the name is generally only used to refer to the smaller, general-purpose cards.


There appeared to be some confusion inside DEC at the time, as various manuals refer to it as "FLIP CHIP", "Flip Chip", "FLIP-CHIP", "Flip-Chip" and "Flip Chip", with trademark and registered trademark symbols.

Flip-Chip families

Flip-chips in different forms and a rainbow of colours, in a PDP-8.

The following FLIP CHIP families ('series', in DEC terminology) were introduced over the years. The various series were colour-coded: the first letter denoted a colour, which was the colour of the plastic which the handle(s) were formed out of.

A series

See the list of DEC parts.

The A stands for 'Amber'. The A series were used for analog functions - ADCs, DACs, amplifiers etc.

B series

The B stands for 'Blue'. First used on the PDP-7, and later in the famous KA10 PDP-10 CPU, they used silicon transistors, and were used as the main logic in the higher-end CPUs.

G series

The G stands for 'Green'. The G series were specialized modules that are part of a specific larger system (e.g. core memory drivers).

K series

The K stands for 'Black' (blacK handles); they were used in industrial control applications, and could tolerate higher voltages, more noise, etc.

M series

See the list of DEC parts.

The M stands for 'Magenta' (a purple colour). When first introduced, they carried the then-new TTL chips; they were first used in the PDP-8/I. Later on, they became quite complex (see list of DEC part numbers). They replaced the R series, which used discrete transistors..

  • Power supply: 5 V
  • Operate at up to 6 MHz

R series

The R stands for 'Red'. Intended to be easy to use, they used diode gates and diode-capacitor-diode circuits; they were slower logic than the B series, but cheaper. They were used extensively in the I/O circuitry of computers.

  • Slower logic than B series, cheaper
  • Used in a variety of systems, e.g. PDP-8
  • Power supply 10 and -15 volts
  • Operational to 2 megahertz
  • Signal level 0 volts, logic 0 and -3 volts, logic 1
  • Typical price $20 to $30

S series

The S series (also with red handles), first developed for the original PDP-8, is identical to the R series, except that its transistors switch faster, and it also used lower resistance resistors, allowing more cards to be wired in series, and also operate somewhat faster.

W series

The W stands for 'White'. These are components that plug into connector block slots that can hold a FLIP CHIP, but have no logic of their own; they are used for input/output to external circuitry.

External links