This web site is being brought to you from a homebrew
computer designed to emulate a PDP-11/34. The core of the
computer took about two years of spare time to design and
build. The machine has a 32-bit wide microcoded instruction
decoder and a 96-bit wide microcoded sequencer with a basic
microcycle time of 250 nanoseconds. The 32-bit CPU uses 8
AMD-2901C 4-bit slice arithmetic/logic units wired to
perform 8, 16, 24, and 32-bit operations. The machine has
4K words of instruction decoder and sequencer microcode.
The machine was coded to emulate the venerable PDP-11/34
instruction set and uses UNIBUS I/O. Additionally the
FP-11 and FIS (PDP-11/35) floating point was also coded.
The basic PDP-11 instruction set programmed in 256 words
of decoder and sequencer microcode. The EIS, FIS, and FPU
microcode required 768 additional sequencer words. This
code was programmed into bipolar proms as the machines native
instruction set. The remaining 3K of decoder and sequencer
microcode is high-speed programmable static ram which can
be loaded on the fly with whatever extension instructions
you might wish to implement (e.g. a block memory-to-memory
move instruction). The machine executes most single operand
register and double operand register-to-register
instructions in .75 microseconds (3 microcycles). The
machine is benchmarked at slightly faster than the
PDP-11/34 (with a FPU). This machine was my development
platform for many microprocessor based projects and uses
the RT-11/TSX-Plus operating systems.
The core computer, which includes a keyboard, a hand pull
paper tape reader, video controller, serial printer interface,
and the power supplies, was constructed on 11 14x20 inch
planes. Each plane contains 4 7x10 inch single sided printed
circuit boards. Each circuit board only distributes power
to wire-wrap sockets for the core processor components. Most
components are small and medium scale TTL devices abundantly
available from 1976-1985. Pictures of the system and
individual panels were taken in 2012. Some video clips of
the computer can also be viewed.
Current System Configuration |
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The current system configuration, as of August 2012, includes
the following items:
1) Core processor with a microprocessor (6800) console
with video output for a CCTV B/W monitor.
The microprocessor includes built in boot code for
the RX01 (DX), RX02 (DY), RK05 (RK), and TM11 (MT)
devices and a general support program KUS (Keyboard
Utility System) which features a non RT-11 file system
used to save/load image files for diagnostics.
A console pass through serial port was initially used
to connect to a LA120 DEC Writer as a printer but now
is connected to a secondary console terminal.
2) peripherals chassis with
a) UNIBUS DD11 backplane
b) ADAC Model 1900 UNIBUS to QBUS converter
c) QBUS DDV11 backplane
3) UNIBUS peripherals
a) CRDS 411 Double-Sided / Double-Density
8" Floppy Disk System
b) TD Systems Incorporated Viking Series
SCSI Host Adapter UDT Disk/Tape Controller
with a Seagate disk drive and
Transitional Technology, Inc. (TTI)
Series 2200 Cartridge Tape System
c) Western Peripherals 131 TM-11 Tape Controller
with Cipher Data Products 100x 9-track
45 ips 800/1600 BPI tape drive
d) DELUA network interface card
e) MDB-11C general parallel interface card
f) Homebrew EPROM and Bipolar PROM programmer
4) QBUS peripherals
a) Heath Kit H-11-5 Serial Port Cards (6)
b) an ADAC 1953BR QBUS repeater interface
connected to a Data Display system
c) a Decmation D201/D100 Z80/8088 Co-Processor
running CP/M and MSDOS 2.1 from virtual
disks
5) Heath Kit H19 terminal with the SUPER-19
replacement ROMs emulating an enhanced
VT100 terminal.
6) SB180 microcomputer with four 5 1/4" floppy disks
connected via serial ports (console and modem).
ZCPR3 is the installed operating system.
Comparative Execution Speeds |
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Some relative execution speeds for compiling the TCP/IP
Package for RT-11/TSX-Plus on the homebrew-11, LSI-11/73,
PDP-11/44, and John Wilson's Ersatz-11 PDP-11 emulator
are interesting:
Homebrew-11 5261 seconds x0.64 ( 7 Apr 2012)
PDP-11/44 3920 seconds x0.86 (25 May 2012)
LSI-11/73 3370 seconds x1 (11 Apr 2012)
(AMD Phenom II @3.6GHz):
Ersatz-11 V2.1 49 seconds x68 (15 Sep 2012)
Ersatz-11 V6.0 18 seconds x187 (15 Sep 2012)