Search found 218 matches

by marcelk
23 Apr 2019, 00:25
Forum: Kit assembly
Topic: Assembling Gigatron the hard way
Replies: 6
Views: 84

Re: Assembling Gigatron the hard way

The simulation is weird. ld $ff definitely makes AC7 high.

I've seen one board that didn't come through the mem test, and it turned out to be an ungrounded condition decoder IC (cold solder joint).
by marcelk
23 Apr 2019, 00:02
Forum: Hardware and software hacking
Topic: Rudimentary vCPU support for the lcc C compiler
Replies: 8
Views: 223

Re: Rudimentary vCPU support for the lcc C compiler

Indeed, there is no heap. There is no malloc. There is no standard lib. There is no non-standard lib either. There is nothing. Wait: there is 1 function in memory at 0x1f0: vReset(). The closest we have to a system description is interface.json, with locations and names of the standardised items. Th...
by marcelk
22 Apr 2019, 23:26
Forum: Hardware and software hacking
Topic: Rudimentary vCPU support for the lcc C compiler
Replies: 8
Views: 223

Re: Rudimentary vCPU support for the lcc C compiler

I have got it working, but with some tricks. I have no idea if any of the stuff below is how it should be done, but I get a GT1 file out... I did this on an older Raspberry Pi with an old installation of Raspbian. Downloading and building LCC: $ git clone https://github.com/pgavlin/lcc $ cd lcc $ gi...
by marcelk
22 Apr 2019, 20:10
Forum: Hardware and software hacking
Topic: Rudimentary vCPU support for the lcc C compiler
Replies: 8
Views: 223

Re: Rudimentary vCPU support for the lcc C compiler

Ok I understand. vCPU isn't really designed with C programs in mind, so many things will never be efficient. But efficiency doesn't matter, because this connects the Gigatron to another domain people are familiar with, and that's what makes it great . FYI: Our port of Tiny BASIC does proper comparis...
by marcelk
22 Apr 2019, 19:53
Forum: Hardware and software hacking
Topic: Rudimentary vCPU support for the lcc C compiler
Replies: 8
Views: 223

Re: Rudimentary vCPU support for the lcc C compiler

Congratulations! Just wow! :o It's the first compiled high level language for the system! This looks like a gift from heaven. I see this can be of enormous help after we have SD card block reading and writing working over the SPI interface: that is to speed up the porting of a FAT library to the Gig...
by marcelk
22 Apr 2019, 17:10
Forum: Hardware and software hacking
Topic: High resolution mode?
Replies: 25
Views: 1073

Re: High resolution mode?

One important detail is that the bit mapping for OUT is optimised for the PCB layout. So D0 isn't receiving ALU0, etc. All our diagrams above are therefore wrong on this aspect. The lower pins are in reverse: Screenshot 2019-04-22 at 19.06.32.png Of course I found out with the multimeter only after ...
by marcelk
22 Apr 2019, 11:33
Forum: Hardware and software hacking
Topic: 10MHz and Beyond!
Replies: 12
Views: 826

Re: 10MHz and Beyond!

I made eye diagrams for a 74HCT board with the 55 ns RAM that comes with the kit, and one with the 10 ns RAM you kindly sent me. I'm not a SMT soldering hero, so I'm surprised it works after the heat abuse I let it undergo. Each trace was captured for somewhere between 1h15m and 1h30m while running ...
by marcelk
22 Apr 2019, 10:33
Forum: Hardware and software hacking
Topic: High resolution mode?
Replies: 25
Views: 1073

Re: High resolution mode?

It's a neat hack. I'm almost tempted to try out this mod in dead bug style, without any PCB. The pin layout between the 2 chips match well for this. Or you can have 10 or so made for ~5 dollars excl. shipping at JLCPCB. For a smaller board, you can win some space by overlapping the "socket" with one...
by marcelk
21 Apr 2019, 23:57
Forum: Kit assembly
Topic: Assembling Gigatron the hard way
Replies: 6
Views: 84

Re: Assembling Gigatron the hard way

Wow, that's cool. It's definitely possible of course. PLEASE share photos. If you're hanging in the mem test's infinite loop, it's pretty close to working already! My original diode decoding looks like this, and believe it or not, I never had any issues with this part of the prototype. IMG_5173.jpeg...
by marcelk
21 Apr 2019, 16:33
Forum: Hardware and software hacking
Topic: High resolution mode?
Replies: 25
Views: 1073

Re: High resolution mode?

I like to confirm the stability at 10 MHz as 60 ns is a huge chunk to chop off the timing budget. My concern is if the high-nibble adder can always keep up in combination with all addressing mode changes. Almost nothing will immediately fail if it doesn't. A sound sample may be off, or Mandelbrot sh...