DEC RL01/RL02 FPGA based Disk-Emulator+

The operation of the RL01/RL02 Emulator is best viewed with a VIDEO via YouTube, however, in the first version, based on the DE1-Board.

****** EMULATOR *****
READER ******
CLONER *****
(WRITER) *****
V2.8E Manual
Program-Start: Download:
All Open Source based on
Quartus V16.1 environment
It also works with the current Quartus version V22.1 or higher.

DE10-Nano Board Implementation
Complete port of the RL-emulator to a SoC/HPS environment based on the DE10-Nano board, primarily consisting of a CYCLON V FPGA with integrated ARM Cortex-A9 CPU. With the new software and firmware version V2.8E, the DE10-Nano Board works as an RL disk emulator (slave mode), RL disk reader / cloner / writer (master mode). The difference between slave and master mode is that in slave mode a real up and running DEC PDP-11 / -8 or VAX system must be available. Mixed operation of emulated and real RL01/RL02 disk drives is possible in both cases without any problems. The software supports reading and writing of the disk image format .DSK. This also enables a simple connection to the SIMH project. A detailed description with examples can be found in the Manual . The additionally required interface board is plugged onto the 40-pin GPIO, see picture. This interface board mainly consists of level converters and provides the 12 RL bus signals with the correct logic-level. The entire firmware and software based on a Quartus V16.1 environment is open source and is also available on GitHub. The LOM data are also available for a possible replica. Of course, it doesn't make sense to write on an old/real RL01/RL02 disk drive. I just implemented it as a personal challenge. In addition, I currently have no access to a real RL01/RL02 disk due to the corona pandemic. Perhaps someone would like to continue the project in this regard.

A full, ready for use configured SD-card-image for the DE10-Nano Board is also available. Download the image and copy it to the SD card with Win32DiskImager, for example. Login: root, PW: pdp11

Project informations

DEC FPGA-based RL01/RL02 Emulator

My challenge in this project is to achieve the vintage software and preserve it on new technology. However the Software is directly dependent on the condition of the disk drive, in my case a DEC RL02 disk drive. The RL02 drive uses removable disk packs to provide 10MB of storage; twice as much as its predecessor, the RL01. After the announcement ~1980 the RL02 turned out very fast to be DEC's all-round disk drive. Although other DEC disk drives like the DEC MSCP-protocol based disk drives ( e.g. RA80 ) would be easier to simulate I nevertheless decided in favor to simulate the RL02 disk drive. My decision was based on three reasons: First: The RL02 drive was available on most of all DEC systems like PDP-8, PDP-11 and VAX systems. Second: The RL02 drive was device-driver supported running on all DEC operating systems, like OS-8, RT-11, RSX-11, MUMBS, RSTS und VMS. Third: My personal challenge and a good chance to jump into the embedded systems world.

Aim of this project: Being able to use the RL02 Emulator on all DEC vintage computer platforms.

To be able to start such a project, we need an up and running environment including a RL02 disk drive and a DEC computer system with disk controller and attached RL02 drive. These RL02 disk drives are already very rare. Unfortunately, most RL02 disk drives don't work any more. Spare parts don't exist anyway. I had it left nothing else to build an operating disk drive from 2 to 3 faulty disk drives left. For me the most difficult part was to adjust the mechanical part via Oscilloscope based on the maintenance instruction following the alignment procedure . I am glad that I was successful and the most important prerequisite for this project was available now. Another problem still is related to the disk packs. A disk pack consists of 2 data surfaces and were pre-formatted by factory and can not be reformatted. After about 25 years, the format information on the surfaces has been already decreased in most cases which may result in Read-Error or in Too-Many-Bad-Blocks.

The project started. Nostalgia is surely also my motivation reason for this project. The main reasons are the love of the vintage computers and also to realize the challenge, something worldwide there is not yet.

Development history

The project started in 2009 and the first release based on the DE1 board in 2012 is clearly visible in a VIDEO . The further development is shown in the following picture. The product was always improved, also because continuously better and cheaper FPGA boards were available. A redundant power supply is provided by the modern and commercially available Power Banks.

Extensions and new versions
RL-Disk Cloninig/Reading

April 2021: Current Version V2.8E

This RL01/RL02 Emulator, rlemulator supports a combination of real and emulated RL01/RL02 disk drives. Thus, it is possible to copy the data from a real RL01/RL02 disk drive into the emulated environment. However, at present there is still a computer system, e.g. a PDP-11 required. With the new extension, this need is no longer necessary. A new program, called clonerl can directly read an RL disk and save it as a .DSK file. The difference between this two applications is that the rlemulator application works in Slave mode and clonerl in Master mode. For the hardware, this means that only(!) the 40pin flat-cable has to be plugged into the RL interface board by 180 degrees, i.e. reversed. However, there is one exception, the Power-OK signal. The necessary change is described in detail in the Manual on page 7.

Previous developments and information

Project Informations