Ths is currently a work-in-progress, with the end goal of actually build one in real hardware some day. But right now I'm just aiming for a simulation which currently is very un-optimized both speed-wise and in regards of the chip count.
Step one is to get the simulation fully working with the built-in non-standard components. Then I'll convert the simulation design to use 74-series chips that still can be purchased - I expect some changes will be requred in regards of triggering at rising or falling edges and whether 3'rd-state outputs are available in the parts. Finally I'll spend some time optimizing the design, with a focus on the total chip count.
| Test tape | Description | Status | Run time |
|---|---|---|---|
| MAINDEC-8E-D0AB-InstTest-1 | Instruction test 1 | OK | |
| MAINDEC-8E-D0BB-InstTest-2 | Instruction test 2 | OK | |
| MAINDEC-8E-D0IB-Basic-JMP-JMS | Basic JMP-JMS | OK | |
| MAINDEC-8E-D0JB-Random-JMP-JMS | Random JMP-JMS | OK | |
| MAINDEC-8E-D0DB-Random-AND | Random AND | OK | |
| MAINDEC-8E-D0EB-Random-TAD | Random TAD | OK | |
| MAINDEC-8E-D0FC-Random-ISZ | Random ISZ | OK | |
| MAINDEC-8E-D0GC-Random-DCA | Random DCA | OK | |
| MAINDEC-8E-D0CC-AddTest | Adder tests | ok? | >30 hrs |
| MAINDEC-8E-D1AA-Memory-Checkerboard | Memory testing | ||
| MAINDEC-8E-D1EA-Memory-Address | Memory testing |
The run time show how long it took running the test on a Late 2013 MacBookPro until the first output on the TTY console (signifying that X number of passes have succeeded). On a real PDP-8/E the times are between five and ten seconds for most tests.
| Tape | Description | Status |
|---|---|---|
| FOCAL-8 | Focal interpreter | Print welcome message, crashes before questions about trig functions |
- /asm/ - Assembly source files. By using the assembler
tools/palthese are made into tape binaries (.bin/.rim) and put in the bin folder - /asm/slyngstad/ - Original interrupt test files from Vince Slyngstad
- /bin/ - Tape files in .bin or .rim format. These are converted into loadable files by the
tools/tape2bin.shutility - /doc/ - Pdf's and textfiles with info about the PDP-8 architecture
- /img/ - ROM/RAM images to be loaded into the simulated RAM
- /sim/ - The .dig files for the PDP-8/X simulation
- /tools/ - Executables like the simulator, compilers and converters
- /pictures/ - Screenshots and other images
I'm using Helmut Neemans 'Digital' for the simulation. It is required to use a pre-release version of it - v0.23-065 or higher. The standard v0.23 release lacks octal setttings that I use.
The prereleases are available from https://infdigital.dhbw-mosbach.de
The main repo of the Digital project is at https://github.com/hneemann/Digital
- 2019-10-07 v0.4 - MAINDECs ok, FOCAL-69 runs successfully
- 2019-09-27 v0.3 - Mostly ok, FOCAL fails
- 2019-09-23 v0.2 - Runs MAINDEC-8E-D0BB (Instruction test 2) successfully
- 2019-09-19 v0.2PA - Runs MAINDEC-8E-D0BB (Instruction test 2) until *2677. Uses 8-slot banked memory to ease changing of test images.
- 2019-09-19 v0.1 - Runs MAINDEC-8E-D0AB (Instruction test 1) successfully
Parts of this repo was written by others.
The MAINDECs and FOCAL is/was of course written and owned by Digital Equipment
The Interrupt tests in /asm/slyngstad/ was written and owned by Vince Slyngstad
In /tools/ there's a copy of Digital written by Helmut Neeman
In /tools/palbart there's the palbart assembler written by Gary A. Messenbrink