68 Katy – 68000 Linux on a Solderless Breadboard

Post by sparky » Tue, Nov 18, 2014, 3:34 PM UTC

VLM wrote: post #21

chubot wrote: post #7

This is amazing! It's pretty surprising to me how little there is on the board. It looks comprehensible. I wonder if you could do this with a modern CPU and RAM. What would it look like?

userbinator's comments are good, and to extend his remarks obviously the solution to clock skew is to simply lower the clock rate. Good luck using a solderless breadboard at 500 MHz digital LOL. But breadboards work just fine at single digit MHz rates. There is a problem. Many processors use dynamic registers and require a clock above a certain rate to refresh the registers. Yes, no kidding, dynamic ram cells as CPU…

Post by bigmessowires » Tue, Nov 18, 2014, 3:58 PM UTC

dfox wrote: post #9

unwind wrote: post #4

The article spoke about a suspected memory leak in setenv(), I assume it uses uClibc but it was a bit light on the details (no source code links in the article, that I could find). I dug up this link: http://git.uclibc.org/uClibc/tree/libc/stdlib/setenv.c?id=30... which I believe is the relevant function. Unsurprisingly for this level of library code, it's not 100% super-obvious or easy to understand. Especially the…

The whole putenv()/setenv()/unsetenv()/environ API is inconsistent hack that is essentially impossible to implement without introducing memory leak in at least one of these operations without introducing some complex additional book keeping. The good news is that there aren't that many reasons to actually use these functions, as only reasonable usecase for modifying environment is changing environment of spawned subp…

Post by [deleted] » Tue, Nov 18, 2014, 5:17 PM UTC

vt240 wrote: post #11

josteink wrote: post #3

That is seriously good work and an amazing DIY project! I remember when I was a kid, trying to just get a pre-made Linux-image boot on my Amiga. I had a 68020 CPU, but due to no MMU and no FPU (neither being "normal" accessories at the time) I just couldn't get the thing to boot at all. Later, when I acquired a 68030 CPU, I at least had the MMU covered, but I was still a kid and didn't have a budget for a FPU. So I s…

Your post just brought back a flood of memories for me about the frustration I went through as a kid trying to port free software to 68k BSD. I started out running MachTen [1] which ran under System 7 on the Mac. There was something odd about the way it did dynamic linking, I can’t remember now, but it just turned any port into a nightmare. I don’t know why it took me so long to figure out there was a mac68k NetBSD,…

Post by lgeek » Tue, Nov 18, 2014, 9:13 PM UTC

sparky wrote: post #31

VLM wrote: post #21

Earlier quoted context omitted.

userbinator's comments are good, and to extend his remarks obviously the solution to clock skew is to simply lower the clock rate. Good luck using a solderless breadboard at 500 MHz digital LOL. But breadboards work just fine at single digit MHz rates. There is a problem. Many processors use dynamic registers and require a clock above a certain rate to refresh the registers. Yes, no kidding, dynamic ram cells as CPU…

Cheapest possible toaster oven + cheap multimeter thermocouple for manual temperature control + {paste flux, solder paste+stencil} works better than you'd think for soldering BGAs. Even honest-to-goodness reflow ovens can be had on eBay for $300-$400 (search "T962"), which would give you another one or two nines of reliability by circulating the air and having more precise temperature control. Schmartboard also makes…

Post by pantalaimon » Fri, Nov 21, 2014, 11:33 AM UTC

zurn wrote: post #30

pantalaimon wrote: post #14

Earlier quoted context omitted.

Wasn't uClinux merged into mainline a long time ago?

You can build it from the mainline git repo, but what you get is a version of the kernel with defining features of Linux/Unix missing.