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guenthert
notsurenymore
I used it a while back to simulate something in the HP 1000 series.
Funny enough, I actually had a machine from that family, along with a variety of other more obscure and niche retro computers and other equipment, sadly I lost all of it, but the reality was it was just costing me a ton of money to get them working again.
pmcjones
The time sharing system on the SDS 940 (https://en.wikipedia.org/wiki/Project_Genie) led to TENEX on the PDP-10.
nikau
As cool as this is, I cant see it being the same experience as using a real Royal McBee jukebox style console with built in oscilloscope
https://upload.wikimedia.org/wikipedia/commons/e/e3/LGP-30_G...
mikewarot
I've had a lot of fun installing and running VAX/VMS on a simulated VAX 11/780.
Automatic versioning of files is still a very nice idea. The general format is
FileName.Ext;1
FileName.Ext;2
Etc.mikewarot
Ugh... I can't get it to build under Termux on my phone.... I need gcc, and don't know how to get it installed. Walking around with a running VMS system in my pocket would be soooo cool. ;-)
My netbook has plenty of horsepower to run it... the phone should too.
mikewarot
Update.... I've got it running... and can telnet into the VAX/VMS 7.2 system in my pocket. ;-)
boringalterego
Same, got it emulating an old tape recovery image of a vax 3100 m76.
tgv
Sounds like a good idea, but it had little value in practice (for me). Since disk space came at a premium back then, it led to constant manual/auto purging.
hulitu
There are areas (CAD) where it made a lot of sense.
Tor3
It's so long since I was using VMS, but one thing I do remember is the constant purging. It was necessary.
musicale
Actually running/using Multics is remarkable. I still want to try ITS to continue my computing archaeology journey.
miki123211
I wonder what the challenges of emulating 36-bit machines on 32 and 64 bit systems are.
Can you even do JIT? You probably don't need to, considering how slow these PDPs actually were, but it's an interesting question nevertheless.
flohofwoe
For ALU ops and address computations, if the 36-bit machines are also using the 2s-complements convention you can just do all computations in 64 bits and ignore the top bits.
For memory accesses you could simply round up the data bus width of emulated CPU to the next power-of-2 as the "host word size". For instance if the emulated CPU accesses memory as 12-bit words, use an uint16_t array on the host CPU and treat the top 4 bits as junk.
JIT-ing probably wouldn't make much of a difference with this approach as long as your host CPU is wider, since you just ignore the top-bits.
When writing a chip emulator, it's actually not uncommon to deal with 'odd' bit widths. For instance a sound chip might have 3- or 5-bit wide counters.
Also, in a language like Zig this stuff is quite convenient since Zig allows integer types of any width (e.g. you can have u3, u5, u36 etc...). Just have to be careful about how those types are represented in memory (e.g. bit-packed or not).
ngcc_hk
Quite a bad thing to contribute and make the whole project to change name as openxxxx. Sad. Do not aware of this last time working on one project.
codezero
Someone on HN must have been browsing similar Tindie listings as I have recently :)
https://www.tindie.com/products/obso/pdp-11-replica-kit-the-...
wkat4242
That's not a recent thing. I've had that replica here for years. I built it during the first lockdown (it only took a day anyway)
I've got their PDP-8 too. Really great kits.
I think the designer was working on a PDP-10 too. But got sidetracked.
aap_
The PiDP-10 will be available in the near future. I've also been working with him on the PiDP-1, which will hopefully be available soon as well.
codezero
It was recent for me! but fair point :)
Glad to hear the kit is great, helps me make up my mind!
wkat4242
It's great indeed. Extremely well designed, great instructions. Even comes with an alignment bar to make sure all the switches end up straight.
And the frontpanel is truly a work of art. The multilayer printing on the plexiglas in particular, but also the surround.
I soldered it all in a few hours but I'm very experienced. Even if you're new to soldering it'll be fine as long as you follow the instructions and take it slow. Double-check every switch type (there's several different types!) and position before you solder it. Make sure all the LEDs fully hit the board so they point the same way, the switches are aligned etc.
It's really an amazing kit. You can feel the love that went into it.
If there's anything I'd change I'd make it 1:1 scale. And the switches don't really feel like the real thing. I've played with a real PDP-11 and the switches really have that "someone paid 100 grand for this back in the day" feel to them. That satisfying affirmative thump. Which is very hard to replicate with off the shelf components of course.
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nxobject
I'm curious – is the Alpha simulation here as a proof of concept, or are its goals beyond that? I don't imagine a simulation of a complex architecture like this would live well in the same framework hosting, say, a PDP-8 simulation.
rnd0
People ask about it from time to time -it seems to be more of a proof of concept than anything else. Patches welcome, of course.
guerrilla
Yeah, really old. No 8086.
zare_st
Use https://86box.net/ There's a ton of hardware profiles embedded. I found my old XT PC which is not that common. Goes up to Pentium era.
It is not perfect tho. My XT has a Plantronics card which is a CGA+, with double memory granting few additional modes, but it's not emulated. There is some historical software targeting this graphics card, even some contemporary retro-indie games.
thristian
> In May 2022, the MIT License of SIMH version 4 on GitHub was unilaterally modified by a contributor to make it non-free, by adding a clause that revokes the right to use any subsequent revisions of the software containing their contributions if modifications that "influence the behaviour of the disk access activities" are made.
That seems weirdly specific. Looking at the actual LICENCE.txt file:
> Any use of this codebase that changes the code to influence the behavior of the disk access activities provided by sim_disk.c and scp.c is free to do that as long as anyone doing this is explicitly not licensed to any subsequent changes to any part of the codebase in the master branch of the git repository (https://github.com/simh/simh) made by Mark Pizzolato after the LICENSE.txt was added to the master branch of repository. Changes that qualify for this restriction at least include: changing the behavior or default of SET AUTOSIZE/NOAUTOSIZE, or any code in scp.c and sim_disk.c or any simulator components that use the sim_disk routines.
I'm guessing this Mark Pizzolato made some changes to the implementation of "disk access activities" that he deemed were important but which other people found controversial, and he wanted to make sure they stayed?
EgoIncarnate
It seems Mark Pizzolato was at the time the primary maintainer and recent contributor (by a large margin) (https://groups.io/g/simh/message/1501).
Mark made a change to how the virtual disk system worked that broke an esoteric use case (using dd to image multiple disk images to an SD, without an actual file system). The user didn't want to use a workaround (specifying the transfer size in the dd command), and proceeded to use twitter to get people to harass Mark. (https://www.bentasker.co.uk/posts/blog/the-internet/toxicity...)
Mark got sick of the harrasment and decided to take his toys and go home.
Toxic user prompts toxic reaction by developer.
userbinator
I'm sure glad I don't work with developers like that, because that complaint makes perfectly reasonable sense to me and I certainly wouldn't consider it "toxic". Expecting a raw disk image file to be the exact size of the virtual device is not at all an "esoteric use case".
Being a prolific contributor doesn't mean you get to force your mistakes on others and cry about it when your decisions come back to bite you. See what Big Tech is doing to us for a great example of what this "feelings-driven design" crap has given us.
Words to live by: "if everyone tells you that you're wrong... maybe you are."
EgoIncarnate
It sounds like there was a config option available to disable the signature addition to the image file ( https://github.com/simh/simh/issues/1059#issuecomment-108689... ). I could see a benefits for having an embedded image signature for preservation and corruption detection issues.
I don't think complaining about the design is toxic, but recruiting uninvolved people on twitter, and harassing out of band certainly is. Also reading the bug thread it seems the person with the issue wasn't the same as the one who instigated the harassment. (https://github.com/simh/simh/issues/1059#issuecomment-108675...)
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dark-star
That "esoteric usecase" was one reason people opposed that change. There are other concerns as well (you can find them if you read the discussion in the GitHub issue linked elsewhere in the comments).
For example, it made SimH alter disk images by itself, without warning, even if you only wanted to use them in a read-only manner.
There was also concern that sticking metadata right into the data itself was bad from a preservation standpoint.
Also there was the point that such things should be opt-in instead of just appearing ferom one version to another, without warning.
All of these concerns were dismissed as unimportant or flat out ignored by Mark. Then he went full overboard with his license change (which made a free project non-free)
Edit: removed incorrect reference to the GPL
trn
> you're not allowed to add additional usage restrictions to GPL software
SIMH is not GPL'd software.
parker_mountain
> an esoteric use case (using dd to image multiple disk images to an SD, without an actual file system).
fwiw this is an _extremely common_ use case. it's literally one of the tasks that dd was created to do
johnklos
Calling the use case esoteric is flatly wrong. It's literally how many disk images across decades of software work. It's how things like vnd(4) work.
Nobody would've cared if it 1) wasn't turned on by default, and 2) didn't destructively change disk images.
It's a bit extreme to call people toxic because they got upset that a deliberate change caused data corruption.
toast0
I don't think getting upset is toxic. But when you don't get the response you want from a small open source project, your next steps shouldn't be to encourage more people to bother the developer(s); that's the toxic behavior IMHO.
mlyle
Nobody cared for a couple of years until one person started recruiting lots of people to bug the developer.
It doesn't destructively change disk images; it appends something to the end. Other usages of disk images are fine: it's only if you want to use the disk images without a filesystem that you run into trouble.
Metadata is useful. Metadata is a whole lot less useful if it's off-by-default.
xvilka
It just resulted in the open and official fork - OpenSIMH[1].
ziotom78
I didn't know this project existed, but that controversy on the license made me curious, and I have had a look at the repository. I stumbled upon this discussion, which shows another controversial decision by the new maintainer regarding the way disk files are managed by the emulator:
eschaton
He’s not “the new maintainer,” he’s “one maintainer” but he decided he knew better than everyone else. Hence why the official SIMH repository is at open-simh.
mlyle
He's the overwhelming majority of contributions to the codebase for the last decade.
What he did was toxic, but in fairness, there was out-of-band harassment coordinated towards him for nearly a year.
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I found the selection of computers emulated to be interesting. Other than fairly popular (in their time) computers like various VAXen, also machines like the SDS 940 of which only a few dozens were ever made. What the the SDS 940 lacks in numbers it makes up in historical importance though (first node on ARPANET, host of first BBS, host used for the Mother of All Demos etc.).