https://github.com/fpw/socdp8

A SoC implementation of a PDP-8/I for the PiDP-8/I console
https://github.com/fpw/socdp8

fpga-soc pdp-8 pidp-8 vintage-computers zynq

Last synced: 5 months ago
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A SoC implementation of a PDP-8/I for the PiDP-8/I console

• Host: GitHub
• URL: https://github.com/fpw/socdp8
• Owner: fpw
• License: agpl-3.0
• Created: 2019-07-21T16:27:03.000Z (almost 6 years ago)
• Default Branch: master
• Last Pushed: 2024-04-07T14:20:15.000Z (about 1 year ago)
• Last Synced: 2024-04-07T15:29:22.404Z (about 1 year ago)
• Topics: fpga-soc, pdp-8, pidp-8, vintage-computers, zynq
• Language: C
• Size: 37 MB
• Stars: 26
• Watchers: 5
• Forks: 2
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

Awesome Lists containing this project

README

        

# SoCDP8   [![Badge Hardware]][Hardware]   [![Badge Software]][Software]

This is an implementation of the 1968 **[DEC PDP-8/I]** on 


a **Xilinx Zynq**, a **FPGA** controller with an **ARM CPU**.

Built on the **[PiDP-8/I Console]** by **Oscar Vermeulen**, 


it acts as a replacement for the Raspberry Pi approach.









![Preview]









## Why a SoC?

Drawback of the **Raspberry Pi + Linux + SIMH** approach:

- **Inaccurate Simulation :** Doesn't allow for single stepping

- **Long Boot Times :** **Linux** takes a few seconds to boot and start **SIMH**

- **Dangerous Shutdown :** In the default Raspberry Pi setup, Linux needs a proper shutdown to avoid corrupting the file system




The **SoCDP8** implements the **PDP-8/I** in **VHDL**, targeting **FPGAs**.




#### Design

The system is modeled exactly as described in the 


**[Maintenance Manual]**  and **Engineering Drawings**.

*The manual is treated as the project specification, registers* 


*and signals are named as described in the book and register* 


*transfers are modeled as specified in the drawings.*




#### Peripherals

Peripherals are implemented on the **ARM CPU** on the **SoC**.

This makes device implementation such as the teletype fairly easy.

Code for peripherals can access the onboard 


**SD Card** to retrieve *tapes*, *disk images*, ..

When connected to the **Ethernet** / **WiFi**, the system, including 


its peripherals, can be controlled with a **Web Browser**.







## Project Goals

- Implementing the system as close as possible to the original specifications.

- Providing a *simple replacement* for the **Raspberry Pi**, 


ideally the project runs on a **SoC** board that snaps into 


the **PiDP-8/I Console** in the same way the **Pi** does.

- Have it be operable through a browser using 


a web socket connection between a web server 


on the **ARM** and the **PDP-8** on the **FPGA**.







## Supported SoCs

The project currently only targets the **Zynq** board 


and utilizes the **Pynq-Z2** for development only.




### Tested Boards

| Board |  |

|:-----:|:-|

| **[ZynqBerry]** | 
 ***Xilinx Zynq 7010*** 

 - `130€` \| Good Availability 

 - **Raspberry Pi** form factor 

 - No free **GPIO** pins 

 - Has the *smallest* **Zynq** 

 |

| **[Pynq-Z2]** | 
 ***Xilinx Zynq 7020*** 

 `132€` \| Good Availability 

 - Raspberry Pi Connectors 

 - Spare **GPIO** pins, such as a 

  **PMOD** pin, useful for sensors
 - Switches, buttons, LEDs 

 - Requires a ribbon cable to 
  fit in the **PiDP-8/I** box 

 |




### Other Boards

| Board |  |

|:-----:|:-|

| **[DE0-Nano-SoC]** | 
 ***Altera Cyclone V*** 

 - `125€` \| International Shipping 

 - **Incompatible** 40 pin connector, 

  requires adapter. 

 - Many free **GPIO** pins 

 - Switches, buttons, LEDs 

 |







## Project Status




### Functional

- **Base System**

- **Timesharing**

- **Data Breaks**

- **Interrupts**

- **EAE**

- **I/O**

*These features pass the **MAINDEC** tests and* 


*can be loaded using the **RIM** / **BIN** loaders.*







### Can Run

- `Focal69`

- `TSS/8`

- `OS/8`




### Peripherals

Implemented in software with only basic functionality.




### Deviations

To have the **PiDP-8/I** work with the **Zynq** boards, 


unfortunately a little modification had to be made.

The `1KΩ` resistors had to be replaced by `220Ω` ones 


to support the **pullup** resistance of the **Zynq** drivers.

Thankfully, `220Ω` is compatible with the **Raspberry Pi** as well so these resistors also support the original system.




[PiDP-8/I Console]: https://obsolescence.wixsite.com/obsolescence/pidp-8

[DE0-Nano-SoC]: https://www.terasic.com.tw/cgi-bin/page/archive.pl?Language=English&CategoryNo=163&No=941&PartNo=1

[DEC PDP-8/I]: https://en.wikipedia.org/wiki/PDP-8

[ZynqBerry]: https://shop.trenz-electronic.de/en/TE0726-03M-ZynqBerry-Zynq-7010-in-Raspberry-Pi-form-factor

[Pynq-Z2]: http://www.tul.com.tw/ProductsPYNQ-Z2.html

[Maintenance Manual]: docs/PDP8I_maintenance_manual_vol1.pdf

[Preview]: pictures/Preview.png

[Hardware]: LICENSE-HARDWARE

[Software]: LICENSE

[Badge Software]: https://img.shields.io/badge/License-AGPL3-015d93.svg?style=for-the-badge&labelColor=blue

[Badge Hardware]: https://img.shields.io/badge/Open_Hardware-1.2-21214e?style=for-the-badge&labelColor=292961