HOMEBREW ONE
[./KL_DEC_J11.jpg] * DEC J-11 @ 10 Mhz
* ? 64? KiB Dual Ported S-RAM ?
There's nothing here yet, (EXCEPT FOR THIS GALLERY OF THE CHIP I GOT!!!
[./DEC_J-11_Gallery]) but I'm buildingn a weird machine around a J-11 CPU.
I want this machine to be self-contained, that is, not just a board with a
serial port.
Ideally, I want to have the entire memory be dual ported S-RAM, and I want all
of it to be exposable as a frame-buffer too.. Maybe.. it'd be kinda neat..
maybe.
RESOURCES
DEC-DCJ11 Users Guide [./datasheet-DEC-DCJ11_Microprocessor_Users_Guide_OCR.pdf]
Article saved to PDF about S-100 cars with same CPU [./S100 Computers - PDP_J11
CPU Board.pdf] from s100computers.com
[
http://www.s100computers.com/My%20System%20Pages/PDP11%20Board/PDP11%20Board.htm]
PDP-SBC-J11-Hack at vcfed.org mforums
[
https://forum.vcfed.org/index.php?threads/pdp-sbc-j11-hack.55374/]
https://www.chronworks.com/J11/ [
https://www.chronworks.com/J11/] (local mirror
of chronworks j11 hack as of 2023-10 [chronworks])
Use EEPROMs as programmable logic [
https://github.com/DusteDdk/eepromlogic]
"BUILD LOG"
2023-10-18 So I've gathered some resources, and a few days ago I found a seller
claiming to sell "new old stock" J-11 chips for about $30, so I thouhgt.. I'll
risk it, for that price, if I get even a defective one, it'll be worth it.
So today the chip arrived, and oh damn, it came in what looks to be a real
(though opened) DEC cardboard box! This might be the real deal.. Upon visual
inspection, I can't tell that the chip has been inserted, there's no markings at
all on the pins, which I'd expect there to be after an insertion, but, what do I
know..
It's absolutely beautiful, so I had a little photo shoot(see link in caps above)
and also documented the packaging with my phone (the crappy looking pictures).
Next up, I've ordered some assorted crystals, my plan is to breadboard it with a
4 mhz crystal (because that was the slowest I could find for next-to-free) and
then bread-board it with an arduino mega. My plan is to try and use the mega for
bootstrapping it, there's enough pins, and I kind of hope the mega will be fast
enough to do _SOMETHING_ with it, at the very least I can pull the pins in a
right enough fashion that I can see the CPU trying to do something. Ideally, I
can emulate a piece of memory and the registers for the console with it, but I'm
not sure it's fast enough, the cpu at 4 mhz and the mega at 16 leaves very
little room for instructions, however, I don't actually know if driving the J-11
at 4 mhz will make it do stuff on the bus at 4 mhz, I know it's microcoded, and
so I hope the bus speed is some division of this. At least I will be able to
verify something with my logic-analyzer on the clock output pin of the J-11.
2023-10-24 I got the crystals and misc stuff I needed to try and at least get it
powered on, no smoke! The scope showed a nice digital clock output at 2 mhz, the
digital logic analyzer confirmed life on both the clock and AIO0..3. Great
success!
During the weekend, I wrote a program for describing complex logic and
generating a binary file that can be written onto an EEPROM and allow it to be
used as a programmable logic device [
https://github.com/DusteDdk/eepromlogic].
I'm going to code the bus control stuff and other glue logic with this pacakge.
[pics/first-clock-s.jpg] [pics/first-clock-l.jpg] [pics/first-powerup-s.jpg]
[pics/first-powerup-l.jpg] [pics/first-analyze-s.jpg] [pics/first-analyze-l.jpg]
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Last edited: 2023-10-28 - No need for a disclaimer, I've done nothing wrong!
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