4 ms·

PDP-11/Hack (2014)

91 points by dcminter 4y ago

ggm 4y ago
I had a ceramic DIP 11/70 but never worked out what to do with it. Eventually I gave it away. It was a single chip afaik not this dual chip on one carrier.
louwrentius 4y ago
Awesome, project, way beyond my skill level. If you are interested in the PDP-11, A youtuber (Usagi Electric) bought a PDP-11/83 and is going to try and get it working again. https://www.youtube.com/watch?v=SB95dlrS5kU https://www.youtube.com/watch?v=SB95dlrS5kU
JPLeRouzic 4y ago
I have a LSI-11 CPU card (M7264), it even has 4K RAM, I wonder if it would be possible to make a similar card with two UARTs for its Qbus?
- kjs3 4y ago
  In theory, sure. In practice, it's a little more complicated than that. First, it would need to talk to the Q-Bus, which is something like "more complicated than the ISA bus, but not as complicated as PCI bus". It's at least very well documented and lots of people have made their own cards (recently, even). There's also the fact that while there are "close but not quite" modern replacements, the bus interface chips DEC used haven't been made in decades and are hard to find without stripping another Q-Bus board (and the ones on eBay are almost certainly fake or fried). Probably fine for a 2-card system to use modern replacements; gets to be a problem with bigger backplanes. Google will get you exhaustive discussions of what is and isn't likely to work ("DS8641 qbus" is probably a good search term to get started). Obviously, easier to find one of the DLV11 Q-Bus serial board variants. One other note, there are multiple versions and revisions of M7264 boards. You'll want to know exactly which one to know what to expect to get it running (e.g. read the doco).
  - JPLeRouzic 4y ago
    Thanks for your remarks. > the bus interface chips DEC used haven't been made in decades and are hard to find People seems to use 7438/74LS38 and 74LS02 with some success. https://forum.vcfed.org/index.php?threads/which-receiver-and-driver-ics-for-q-bus.64369/ https://forum.vcfed.org/index.php?threads/which-receiver-and... An example could be seen from page 116 in February 1980 edition of Byte magazine: https://ia600307.us.archive.org/11/items/byte-magazine-1980-02/1980_02_BYTE_05-02_Graph_Theory.pdf https://ia600307.us.archive.org/11/items/byte-magazine-1980-...
    - kjs3 4y ago
      Like I said, the alternatives can certainly work. Until they don't. And some alternatives work better than others. I checked some notes and found the Eric Smith[1] page where I learned about this. Eric has been around the retrocomputing and DEC world for a long time. I also have a note that the Russian КР559ИП3 is the equivalent to/copy of the original driver chips. I've never seen one. [1] http://www.brouhaha.com/~eric/retrocomputing/dec/interfacing/chips.html http://www.brouhaha.com/~eric/retrocomputing/dec/interfacing...
ChicagoDave 4y ago
I believe there's a guy that attends the THE VINTAGE COMPUTER FESTIVAL MIDWEST that had this working. I saw something like it 2 years ago.
dingosity 4y ago
I especially love how Brent is using (what looks like) a VT220 to communicate with the ODT.
kjs3 4y ago
This is really nifty work, and I wired it up a couple of years ago when he published and it worked with one of my DCJ-11s. Fooled around in ODT for a whole afternoon. Unfortunately, most of the PDP-11 operating systems expect a lot of non-trivial system infrastructure in place to boot. I thought about doing something in ROM (maybe a Forth?), but moved on to other projects.

PDP-11/Hack (2014)

91 points by dcminter 4y ago

ggm 4y ago

I had a ceramic DIP 11/70 but never worked out what to do with it. Eventually I gave it away. It was a single chip afaik not this dual chip on one carrier.

louwrentius 4y ago

Awesome, project, way beyond my skill level. If you are interested in the PDP-11, A youtuber (Usagi Electric) bought a PDP-11/83 and is going to try and get it working again. https://www.youtube.com/watch?v=SB95dlrS5kU https://www.youtube.com/watch?v=SB95dlrS5kU

JPLeRouzic 4y ago

I have a LSI-11 CPU card (M7264), it even has 4K RAM, I wonder if it would be possible to make a similar card with two UARTs for its Qbus?

kjs3 4y ago
In theory, sure. In practice, it's a little more complicated than that. First, it would need to talk to the Q-Bus, which is something like "more complicated than the ISA bus, but not as complicated as PCI bus". It's at least very well documented and lots of people have made their own cards (recently, even). There's also the fact that while there are "close but not quite" modern replacements, the bus interface chips DEC used haven't been made in decades and are hard to find without stripping another Q-Bus board (and the ones on eBay are almost certainly fake or fried). Probably fine for a 2-card system to use modern replacements; gets to be a problem with bigger backplanes. Google will get you exhaustive discussions of what is and isn't likely to work ("DS8641 qbus" is probably a good search term to get started). Obviously, easier to find one of the DLV11 Q-Bus serial board variants. One other note, there are multiple versions and revisions of M7264 boards. You'll want to know exactly which one to know what to expect to get it running (e.g. read the doco).
- JPLeRouzic 4y ago
  Thanks for your remarks. > the bus interface chips DEC used haven't been made in decades and are hard to find People seems to use 7438/74LS38 and 74LS02 with some success. https://forum.vcfed.org/index.php?threads/which-receiver-and-driver-ics-for-q-bus.64369/ https://forum.vcfed.org/index.php?threads/which-receiver-and... An example could be seen from page 116 in February 1980 edition of Byte magazine: https://ia600307.us.archive.org/11/items/byte-magazine-1980-02/1980_02_BYTE_05-02_Graph_Theory.pdf https://ia600307.us.archive.org/11/items/byte-magazine-1980-...
  - kjs3 4y ago
    Like I said, the alternatives can certainly work. Until they don't. And some alternatives work better than others. I checked some notes and found the Eric Smith[1] page where I learned about this. Eric has been around the retrocomputing and DEC world for a long time. I also have a note that the Russian КР559ИП3 is the equivalent to/copy of the original driver chips. I've never seen one. [1] http://www.brouhaha.com/~eric/retrocomputing/dec/interfacing/chips.html http://www.brouhaha.com/~eric/retrocomputing/dec/interfacing...

ChicagoDave 4y ago

I believe there's a guy that attends the THE VINTAGE COMPUTER FESTIVAL MIDWEST that had this working. I saw something like it 2 years ago.

dingosity 4y ago

I especially love how Brent is using (what looks like) a VT220 to communicate with the ODT.

kjs3 4y ago

This is really nifty work, and I wired it up a couple of years ago when he published and it worked with one of my DCJ-11s. Fooled around in ODT for a whole afternoon. Unfortunately, most of the PDP-11 operating systems expect a lot of non-trivial system infrastructure in place to boot. I thought about doing something in ROM (maybe a Forth?), but moved on to other projects.