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Web PDP emulation

RetroNewbie

RetroNewbie

Experienced Member
Joined
Dec 13, 2023
Messages
125
Location
Italy
Hello everyone, I wanted to share my project in this forum in order to get feedback and suggestions about it, from expert users of such systems. The broader aim of the project is to be an online interactive museum, and I'm starting by emulating a PDP-11 and I will eventually move on to a PDP-1 (and maybe 8), before moving to other historical minicomputers/mainframes.

The PDP-11 emulation aims for an original setup with a PDP-11/20 dated around ~1972 with some peripherals. Since the aim is to be a museum setting, I would like to stick with time accuracy, so I'm aware that things such as the VT100 won't be in the final version. What I'm particularly interested in is getting feedback about the sound design and general look and feel, and any inaccuracies you may find (there are many of which I am aware of, but I'm sure there are many that I don't). Timing accuracy for peripherals devices is also somewhat of a goal, even if not a top priority. Also suggestions about what you would personally like to be added to play around with are very welcome!

Booting into RT-11 and operating the TU56 dectape. (Using ASR33)

View attachment part1.mp4

Booting into RSTS-11 and concurrent execution:

View attachment part2.mp4
 
I have been thinking along the lines of something similar but using VR (e.g. Metaquest or Apple Vision).

I just don't have the time to do it.

Something like what you appear to be doing would also be welcome...

Dave
 
I think this is great. Well done!

I think the inclusion of sound is particularly important. Whilst SIMH and other emulators are fantastic, they don't do a good job of representing the physical and environmental aspects of old computers - the clatter of a teletype, the back-forth spooling of a reel-to-reel tape, a set of drives spinning up, the rack fans, the air con! The sound and realistic speed are so important to understanding and appreciating the constraints and realities of working with large computer systems in the 70’s and (in my specific experience) the ‘80’s.

Good work.

Suggestions:

- sound for drives (spin up and down)
- rack fan sound
- background air con sound
- Line printer perhaps?
- How about being able to select the vt100 and get directly into a SIMH environment with blinkenlights front panel?!
- How realistic to be able to ‘type’ on the ASR33?

Keep going!
 
daver2 said:
I have been thinking along the lines of something similar but using VR (e.g. Metaquest or Apple Vision).

I just don't have the time to do it.

Something like what you appear to be doing would also be welcome...

Dave
Click to expand...
I see how a VR application would be even more immersive, but I decided to implement it as a website to make it as accessible and easy to use as possible.

But it is very time consuming, thankfully I've been managing to work on and off on this while studying.
 
Rob G5RMP said:
I think this is great. Well done!

I think the inclusion of sound is particularly important. Whilst SIMH and other emulators are fantastic, they don't do a good job of representing the physical and environmental aspects of old computers - the clatter of a teletype, the back-forth spooling of a reel-to-reel tape, a set of drives spinning up, the rack fans, the air con! The sound and realistic speed are so important to understanding and appreciating the constraints and realities of working with large computer systems in the 70’s and (in my specific experience) the ‘80’s.

Good work.

Suggestions:

- sound for drives (spin up and down)
- rack fan sound
- background air con sound
- Line printer perhaps?
- How about being able to select the vt100 and get directly into a SIMH environment with blinkenlights front panel?!
- How realistic to be able to ‘type’ on the ASR33?

Keep going!
Click to expand...
Thank you!

That's exactly the reason why I started this project and what I'm aiming for, with the added bonus of running in a website, making it more accessible than traditional emulator such as SIMH (no installation or commands to learn, other than the ones of the computer itself).

Also a big thank you for the suggestions, sounds are a big missing part of the emulator and I am definitely going to address it. Just like with 3D modelling I will have to learn the tools of the craft from zero and I have many doubts about the right approach for it. I wonder if trying to make synthetic noises from zero to match real ones is even possible or if I should find someone with real hardware to record some audio to use. I've used both methods in the little sounds that there are, with mixed result.

Line printer is definitely feasible, even the ability to save the paper output as an image file should be easily implementable.

I didn't get the suggestion about SIMH/vt100 and blinkenlights, I am not using SIMH as the underlying emulator but one written from scratch so not sure if whatever you were suggesting is feasible

I didn't really get "How realistic to be able to ‘type’ on the ASR33?". Sorry english is not my first language.
 
daver2 said:
Rob is asking "can the human operate the keys on the ASR33 to enter commands etc."?

Dave
Click to expand...
Oh I see thank you, in that case, I will definitely add provisions to switch between LOCAL-LINE mode and any other functions the ASR33 might have other than normal "terminal" input/output, right now it's just a model that sends/receive characters. Not sure if'll implement such changes with special key binds or actual user clicks on the real buttons/switches.
 
daver2 said:
So you can already 'type' on your ASR33 keyboard (in LINE mode) to interact with the PDP-8 software?

Dave
Click to expand...
Yes, in the attached videos, that is me typing on my keyboard as if I were typing on the ASR33, using RT-11/RSTS-11. The basic program written in the second video in RSTS on the ASR33 was being written by me on my keyboard (so sent through the emulator as if it was coming from the serial line input). (If that's what you are asking)
 
RetroNewbie said:
Thank you!

That's exactly the reason why I started this project and what I'm aiming for, with the added bonus of running in a website, making it more accessible than traditional emulator such as SIMH (no installation or commands to learn, other than the ones of the computer itself).

Also a big thank you for the suggestions, sounds are a big missing part of the emulator and I am definitely going to address it. Just like with 3D modelling I will have to learn the tools of the craft from zero and I have many doubts about the right approach for it. I wonder if trying to make synthetic noises from zero to match real ones is even possible or if I should find someone with real hardware to record some audio to use. I've used both methods in the little sounds that there are, with mixed result.

Line printer is definitely feasible, even the ability to save the paper output as an image file should be easily implementable.

I didn't get the suggestion about SIMH/vt100 and blinkenlights, I am not using SIMH as the underlying emulator but one written from scratch so not sure if whatever you were suggesting is feasible

I didn't really get "How realistic to be able to ‘type’ on the ASR33?". Sorry english is not my first language.
Click to expand...
i think if you're looking for realistic sound samples you could probably ask around here, chances are good that someone owns the hardware you want to sample and would be happy to help with recording. if not an individual collector we have representatives from a couple of computer museums on here who may also be able to help. a decent field mic like a zoom h2n can be had for pretty cheap on ebay and they're simple to use.
 
hush said:
i think if you're looking for realistic sound samples you could probably ask around here, chances are good that someone owns the hardware you want to sample and would be happy to help with recording. if not an individual collector we have representatives from a couple of computer museums on here who may also be able to help. a decent field mic like a zoom h2n can be had for pretty cheap on ebay and they're simple to use.
Click to expand...
Rob G5RMP said:
@vaxorcist has an interest in adding sound to simulations and might be able to help with this.

Rob.
Click to expand...
Thank you for the hints, I'll probably go about doing it this way then. Especially for sounds such as the RK05 spinning/TU56 I wouldnt know where to start otherwise.
 
Rob G5RMP said:
I think this is great. Well done!

I think the inclusion of sound is particularly important. Whilst SIMH and other emulators are fantastic, they don't do a good job of representing the physical and environmental aspects of old computers - the clatter of a teletype, the back-forth spooling of a reel-to-reel tape, a set of drives spinning up, the rack fans, the air con! The sound and realistic speed are so important to understanding and appreciating the constraints and realities of working with large computer systems in the 70’s and (in my specific experience) the ‘80’s.

Good work.

Suggestions:

- sound for drives (spin up and down)
- rack fan sound
- background air con sound
- Line printer perhaps?
- How about being able to select the vt100 and get directly into a SIMH environment with blinkenlights front panel?!
- How realistic to be able to ‘type’ on the ASR33?

Keep going!
Click to expand...
Ah yes, the sounds of a nice LA-120, when RSX starts up. But, there's nothing like the sound of a giant IBM line printer literally spitting out reams of paper at (based on my memory) seems like 60mph.
 
In the last couple of days I had lots of free time and I grinded a PDP-8 emulator + 3D models in just 3/4 days which would have been unthinkable just a couple of months ago, all the time spent making a common environment to use with any computer really paid off. Here is a demo video of the straight 8 running a simple echo program with the ASR33. The emulator is just missing the memory expansion and the IOT instructions meant for the processor but other than that it seems to be working fine (and cycle accurate). Definitely one of the easiest emulator to implement out there, simple state machine well described in the documentation. Any straight 8 peripherals/usage stories that you may want to share to get idea for the emulation?

View attachment Screencast from 2026-01-29 20-11-09 (online-video-cutter.com).mp4
 
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