antiquekid3
Veteran Member
If someone's willing to help with the hardware, I'm very willing to tackle the software!
Kyle
Kyle
Flip Chip Tester for Negative LogicThe Flip Chip Tester has become long neglected. Finish that work on the
negative logic tester, or abandon it.
The Flip Chip Tester needs more module descriptions/test cases.
Possibly related to that is an old idea about using handlers in dumprest.
How best to do that with respect to non-standard media, like reading
LINCtape on TD8E?
SIMH could use LINC/PDP-12 emulation.
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Vince
I've been running through the SIMH PDP-8 emulation, adding code to simulate LINC instructions. It is helping me deepen my understanding of the LINC instruction set. It also raises questions about what we mean by emulation for a machine that's meant to control lab equipment. The I/O and co-processor scheme is also quite different. Both the LINC and the PDP sides are full of quite complex CISCy instructions.SIMH could use LINC/PDP-12 emulation.
This is beyond my capabilities to do, but I could help and compare behavior to a real PDP-12.
Thanks!What’s been helpful to me in the past is:
Documentation / diagrams that have been preserved or recreated (especially accurate/corrected ones)
Preserved original software and the tools for preserving old software
Helper tools (software and hardware) to get a system running
Replacement or recreation parts for unobtainable originals, or unreliable/degrading parts (disks, tapes)
Knowledge of common failure modes, how to identify and fix
This is what has me, personally, excited about this project. Being able to make emulated replacements for missing parts of a larger system, while leaving the bits that are present, working as intended.And I should add that, to me, the beauty of this sort of project (that is, describing a PDP-8/I system in Verilog at the Flip-Chip™ module level) means that you can scribe a line at any point between gate array hardware and real DEC hardware.
Don't have a TC08? Great, there's a tested, synthesizable model of that waiting for someone to put on a board and hook up to a real 8/I. Don't have a TU55 but have a controller? There's a tested model of that, too (you'll probably want to bypass the G888s, though). Don't have extra memory, an EAE, etc.? Yep, those are tested and operational as well.
May or may not be viable for this project, but I just learned of these today... the "colorlight 5A-75E"; a chinese board intended for some sort of lighting thing, but with what seems to include a reasonably capable FPGA, a whole slew of 5v I/O, support from an open-source toolchain, and what appear to be plentiful stocks from various sources despite the shortage. Biggest downside, the 3.3v->5v I/O level shifters are HC parts, which would need replacing with 74HCTXX parts in order to properly interface with the 74XX or 74LSXX ones in a real -8. Surface mount, so annoying, but not impossible.Well, theoretically yes. No hardware has been constructed to support that yet. The only hardware the model has been run on is a PYNQ board, as I was able to leverage another 8/I FPGA implementation to use the PiDP-8/I front panel.
Given the chip shortage, finding an appropriate development board for others to play with may be challenging. Optimally, I'd find something that's a regular old FPGA (or a number of ATF1508s for our friend Vince!) and not the Zynq SoC with its dual ARM cores. Even though I'm not using those, the fact they exist alongside the 8/I implementation disgusts me!
I do remember seeing those a while back. Thanks for pointing them out again! Seems like an interesting choice to play with, for sure. Might have to pick up a few!May or may not be viable for this project, but I just learned of these today... the "colorlight 5A-75E"; a chinese board intended for some sort of lighting thing, but with what seems to include a reasonably capable FPGA, a whole slew of 5v I/O, support from an open-source toolchain, and what appear to be plentiful stocks from various sources despite the shortage.
I wondered how to get inputs into the FPGA? Does it have to be networking?Seems like an interesting choice to play with, for sure. Might have to pick up a few!
Probably have to un-ground the DIR pin or some such.Wait a second...those are HC245, which are transceivers. So in that case, they should be just as capable as inputs as they are outputs!
From the reading I did, they seem to be worried about the CMOS inputs not being driven to their respective rails. One source suggested leaving the CMOS parts, but powering them from the 3V supply (and lifting DIR). Not sure how much current the 3V supply is prepared to deliver, though.The documentation on the GitHub link suggests you have to replace them with 74LVC245s, along with isolating both VCC and DIR. I don't see a schematic, so I'm not sure what the deal is with VCC.