Module Comparisons Third-Party Products Functional Information

DCT11 Processors


The DCT11 is a single-chip microprocessor, with a 16-bit address bus and a user-selectable 16-bit, or 8-bit data bus. It was used in the SBC-11/21 line of Q-bus single board computers, often referred to as FALCONs, as well as several other peripheral devices. FALCONs were sold strictly as OEM products for industrial control and other related applications.

The table below contains a breakdown and comparison of the DCT11-based single board computers.

DCT11 Processors and Their Capabilities
Processor SBC-11/21 SBC-11/21+
Module Number M8063-AA M8063-BA M7676-AA
Model Number KXT11-AA KXT11-AB KXT11-BA
Introduced 1981 1982 1984
Discontinued 1987 1989
Module Size Dual Dual Dual
Chipset T11 T11 T11
Est. Performance (VUP) 0.25 0.25 0.25
Clock Period (ns)5 203 203 203
Q-bus Address Size 16-bits 16-bits 16-bits
Q-bus Interrupts 1-level 1-level 1-level
RAM Capacity 64 KB 64 KB 64 KB
Onboard ROM optional1 optional1 optional2
Onboard RAM 4 KB3 4 KB3 16 KB4
Onboard LTC yes yes yes
Onboard LTC Register no no no
Onboard Serial Ports 2 2 2
Onboard Parallel Port yes yes yes
ODT Microcode no no no
ODT Firmware optional optional optional
Self-Test Diagostics no no no
Memory Refresh no no no
Termination 220 ohms 220 ohms 220 ohms
AC Bus Load 2.4 2.4 2.7
DC Bus Load 1 1 0.5
+5V Load 2.5 A 2.5 A 2.8 A
+12V Load 0.06 A 0.06 A 0.06 A

1 Up to 32 KB is supported, using four 8 KB EPROMs.
2 Up to 48 KB is supported.
3 Up to 36 KB is supported, using four 8 KB SRAMs.
4 Up to 48 KB is supported, using four 8 KB SRAMs.
5 Clock frequency = 1 / Clock Period (e.g. 1 / 400 ns = 1 / 0.0000004 = 2,500,000 Hz, or 2.5 MHz)


The KXT11-AA and KXT11-AB are nearly the same board, but with slightly different artwork. The KXT11-AA uses etch revision C, whereas the KTX11-AB uses etch revision D. The KXT11-BA is a completely different board and is generally referred to as the FALCON+.

The production dates are a bit murky, but as early as 1983, DEC was calling the KXT11-AB the FALCON+, with 16 KB of RAM. This board actually only has 4 KB of onboard RAM, which is soldered to the board. This board can, however, support more RAM in either set of open sockets. The M7676 had 16 KB of onboard RAM and was introduced several years later.

KXT11-AB was very poorly documented, until its user guide recently surfaced. None of the DEC service manuals or catalogs discuss this board - only the KXT11-AA. With the new artwork, the curcuit board has different identifiers for the chips and jumpers. Some of the jumpers have slightly different functionality, compared to the KXT11-AA.

Any of these boards can function as Q-bus masters, or as standalone computers, which provides the system designer quite a lot of flexibility. The M8063 has a less cluttered memory map and therefore, may be more desirable for managing a larger Q-bus system. The M7676 might be better suited for standalone applications.


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