Hacker News Reader

Comment by PhilWright | Hacker News Reader

Hackaday project owner here...

The idea of the project is the fun of playing around with electronics, something I have not done before, and trying to understand everything about a real computer. Starting with the CPU and then building it out with a simple graphics card. After that create an assembler/compiler for RISC-V and write a small OS. Yes, all of these will be relatively simple and not of a commercial standard, but building a machine and watching it run with all the hardware and software written from scratch is the longer term goal.

View on HN

> building a machine and watching it run with all the hardware and software written from scratch is the longer term goal.

This is an awesome & crazy project! I'll be watching. Would love to read a little bit about how much time it's taking as you go, and how it balances against your work & life.

Ever since I was an undergrad many moons ago, I thought a 4-year CS degree that ran on this same premise would be amazing. Say, spend your first year learning hardware logic and building a CPU. Year 2 is a basic operating system & compiler. Year 3 networking & a graphics system, and year 4 maybe a game or application or research project of the student's choice. Or something like that. Wouldn't it be cool to graduate having built your own computer from the ground up?

A couple points. First you could use surface mount ICs and fit a whole lot more circuitry onto one board. Soldering is harder but it should be better in every other way.

Second. The register file could be implemented with far fewer chips if only a single output was used. The A and B register select bits would need to go through a quad 2-1 multiplexor and the output would need to be latched for either A or B and some sequencing logic added to make it work. In other words it would take 2 cycles to read from both A and B operands.

Oh, and don't forget that in RISC-V register 0 is always read as zero so no actual storage is needed for that one.

Once you get over the initial effort of switching to surface mount and get a toaster oven/griddle setup, it can actually be quite a lot faster, especially for doing stuff in quantity. Using a stencil you can quickly place paste for all components, then hand place all components and bake it. Of course finding solder bridges and debugging can become a bit tricky...

Desoldering is all much faster if you have hot air and some tweezers.

In other words it would take 2 cycles to read from both A and B operands.

Or you could read one register on the rising and the other on the falling edge of the clock, if timing permits. A lot of real microprocessors were designed with this techinque.

Did you consider using KiCAD or another open EDA tool instead of Eagle?

Have to admit I never heard of those two tools! Given I use PCBWay for cheap production of boards I can only create boards that are 100m x 100m at a max anyway. So the Eagle restriction of free use up to 100m x 80m is not bad.

This is awesome. One tiny request: please change the board dimensions text on the page to "100mm x 80mm", or "100x80 mm" or something.

I had to stop and think about this for a second or two, since I wondered what on Earth you were doing building 100-meter boards. Units matter, and the symbol for "millimeters" is "mm". Thanks.

Mods: also it would be awesome to have "RISC-V" in the title.

It's possible to work around the restriction easily. This tool (https://github.com/p12tic/eagle-brd-merge) can move a single Eagle board around, so whenever you want to move a component outside the allowed window you simply move the board. You can panelize the boards without any board size restriction using that tool too.

cool project.. I'm curious about your experience working with China PCB manufacturer. The costs seem low from my experience ($10 for 10 boards + $25 shipping). Was the quality there? How fast was the shipping? Did you attempt any homebrew PCB etching?

I have ordered from them 3 times and each time they arrived in ~1 week to Australia. Takes 2 or 3 days for them to be made and then another 3 or 4 days to be delivered by DHL. I have not had problems with any boards so far. I have never ordered from anyone else so I have no idea how they compare to others but for a home project with simple designs they are just fine. You can combine orders for several different boards into a single postage so it becomes even better value.

I'm not the author, but I've etched my own boards. My graduate thesis project contained a couple dozen homebrew boards by the time all was said and done.

I used a photo-resist process based on transparencies that I made in the department Xerox machine.

The biggest improvement in moving to real manufactured boards was plated-through holes. For that reason alone, I wouldn't go back. Not only are boards easier to route with PTH's, but they are also more robust -- it's harder to lift a pad off the board when removing a component.

Solder mask is a boon as well, especially for surface mount.

Dirtypcbs[1] did a bang up job with amazingly fast turn around. Even got 4 extra boards; we used them for our alienflight[2] builds.

[1]: http://www.dirtypcbs.com [2]: https://www.youtube.com/watch?v=6LCuZCmttIQ

I ordered several times from shenzhen2u. I had a few questions and some issues at first with their store. I always got a friendly (and useful) answer within 24 hours. Actually better answers, than what I got in Europe (some of them very expensive in comparison). Quality for my requirements was always better than expected. E.g. I made several boards for a Raspberry Pi and the through holes were all fine (on all boards). I had zero issues to put them on top of the 2 x 20 header of the Raspberry Pi.

This is great! I remember as a teenager back in the 80s I built a 4-bit CPU (actually, not much more than an ALU really) using 74-series chips I'd salvaged in part from old mainframe boards I found at my local scrapyard.

I loved inventing the instruction set, which made me realise why opcodes are encoded the way they are. Probably one of the best learning experiences I ever had.

Fantastic. I'll follow this with great interest, I've had the same urge to make my own 'relatively simple everything' for years, but not even close to this (already) in execution.

This is neat. I'm looking forward to reading updates.

Reply on news.ycombinator.com