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PDP-8 Summary of Models and Options (posted every other month)
Section - What is a PDP-12?

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Date of introduction:  1969 (February or earlier).
Date of withdrawal:    1973.
Total production run:  3500?
Price: $27,900

Technology:  DEC M-series flip Chip modules, as in the PDP-8/I.

Reason for introduction:  This machine was developed as a follow-up to
	the LINC-8.  Originally it was to be called the LINC-8/I, but
	somehow it got its own number.  In effect, it was a PDP-8/I with
	added logic to allow it to execute the LINC instruction set.

Reason for withdrawal:  The LAB-8/E and the LAB-11 (a PDP-8/E and a
	PDP-11/20 with lab peripherals) eventually proved the equal of
	the PDP-12 in practice, and LINC compatability eventually proved
	to be of insufficient value to keep the machine alive in the
	marketplace.
		
Compatability:  This machine is fully compatable with the PDP-8/I, with
	additional instructions to flip from PDP-8 mode to LINC mode and
	back.  IOT 0 could enable the API, causing trouble with later
	PDP-8 code that assumes IOT 0 is "Clear all flags".  Also, the
	DECtape instruction DTLA (6766) becomes part of a stack-oriented
	extension to the instruction set, PUSHJ, on late model (or field
	updated) machines with the KF12-B backplane.

	The PDP-12 supported trapping of those LINC functions that were
	emulated by software on the LINC-8.  This allowed it to run many
	LINC-8 bootable systems (but not all, due mostly incompatabilities
	in LINKtape support), and it allowed such things as emulation of
	LINKtape instructions for reading and writing disk.

	The TC12F Linktape controller could, with appropriate software,
	read or write DECtape.  This support is unreliable, and is not
	software compatable with the TC01 or TC08 DECtape controller.

Standard configuration:  PDP-8/LINC CPU with 4K of memory, plus 110 baud
	current loop interface, plus output relay registers.  In
	addition, the standard configuration included either two TU55 or
	one TU56 drive, with a PDP-12 only controller allowing it to
	handle LINCtape.  In addition, a 12" scope was always included,
	with a connector that can connect to a second scope.

Expandability:  An analog to digital converter and multiplexor was needed
	to fully support knob-oriented LINC software.

	Other options included:

	-- the KW12 programmable lab clock.
	-- additional TU55 or TU56 drives (up to 8 transports).
	-- the BA12 expander box
	-- the PC05 paper tape reader punch (needs the BA12).

	Fabritek made a 24K memory box that could be added to a PDP-8/I or
	PDP-12.

Survival:  A few PDP-12 systems are in operating condition.

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Top Document: PDP-8 Summary of Models and Options (posted every other month)
Previous Document: What is a PDP-8/L?
Next Document: What is a PDP-8/E?

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Last Update March 27 2014 @ 02:11 PM