DCT11 Processors
Overview
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)
Summary
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.
References
- M8063 Falcon SBC-11/21 Single-Board Computer User's Guide, Second Preliminary, December 1981 (EK-KXT11-UG-PR1)
- SBC-11/21 Single-Board Computer User's Guide, First Edition, June 1982 (EK-SBC01-UG-001)
- SBC-11/21 PLUS Single-Board Computer User's Guide, First Edition, March 1984 (EK-SBC02-UG-001)
- LSI-11 Systems Service Manual, January 1985 (EK-LSIFS-SV-005)
- Digital Equipment Corporation Option/Module List, April 21, 1983
- Digital Equipment Corporation Option/Module List, June 13, 1991
Additional Resources
- MicroNote 5 - Q22 Compatible Options
- MicroNote 7 - User Defined Memory Maps for the FALCON and the FALCON+
- MicroNote 15 - Q-Bus Hardware Bootstraps
