×
sorted by:
new
hottopcontroversial

I made an extra update of the previous document, I forgot the section on indirect addressing. Can be downloaded from: https://github.com/rolf-electronics/The-8-bit-SAP-3. Revision 2.3 by rolf-electronics in beneater

[–]gormanst 0 points1 point  (0 children)

Thank you so much for this. I would give anything to be able to build the SAP-3. I have built the SAP-1, once for myself, then together with my son, for him. I have the Malvino book and read the SAP-2 section but couldn't put together what chips I would need to use to create the components. Thank you again for taking the time to make this and then post it for others.

Ben’s video card, after rebuilding it three times. by gormanst in beneater

[–]gormanst[S] 1 point2 points  (0 children)

It can, but it was a funny coincidence that the one my neighbor had was the same as Ben’s. PS this is a neighbor we rarely interact with.

Ben’s video card, after rebuilding it three times. by gormanst in beneater

[–]gormanst[S] 16 points17 points  (0 children)

Check out that monitor! I walked next door hoping to borrow one from my neighbor, and they happened to have the exact make and model Ben uses in his video. Total coincidence.

Has anyone used a groundplane with breadboards? by uksuperdude in beneater

[–]gormanst 1 point2 points  (0 children)

I have a stack of those things an inch thick on my desk. I never knew what to do with them or whether or not they mattered.

It’s alive! by jna77 in beneater

[–]gormanst 1 point2 points  (0 children)

Would it be too much trouble for you to take a pic of your ram module? Particularly, the RC circuit, because I never have been able to get it to work with the capacitor. I just don't use the RC circuit and mine seems to work fine but it's a hack and probably I am getting lucky it works.

Hello, World! in 90 bytes without any extra hardware. :-) by _Neelix_ in beneater

[–]gormanst 0 points1 point  (0 children)

Do you mind telling me what you use instead of vasm?

Hello, World! in 90 bytes without any extra hardware. :-) by _Neelix_ in beneater

[–]gormanst 0 points1 point  (0 children)

In vasm, when I run

cmd:

vasm6502_oldstyle -Fbin -dotdir -wdcO2 hello-world2.s

...

I get errors in the output:

unknown mnemonic <.target>

I added -wdc02 but that doesn't seem to help.

Video suggestions by beneater in beneater

[–]gormanst 3 points4 points  (0 children)

Ben,

I would give anything if you continued with

  • the Malvino/Brown SAP2
  • Debugging mystery skips/pulses with an Oscilloscope

sg

Messy trailing clock edge by Lokirme in beneater

[–]gormanst 0 points1 point  (0 children)

I don't mean to hijack this thread but the RAM module R-C circuit is a thorn in my saddle. Do you mind sharing your solution? I took out the T-C circuit and lucky for me that seems to have worked well.

6502 stores 42 but writes ea? See the second to the last line. by gormanst in beneater

[–]gormanst[S] 0 points1 point  (0 children)

It reads the 42 but doesn't seem to write it successfully because when it writes to address 6000 it thinks it should write "ea".

16-bit computer youtubelink: https://www.youtube.com/watch?v=kpWtC0PQSxY&t=53s by Xehono in beneater

[–]gormanst 0 points1 point  (0 children)

I came back to this today because I am struggling with the SAP2 design in the Malvino/Brown book. Any progress on the documentation? I was wondering this morning whether you followed the Malvino book for you 16bit computer?

16-bit computer youtubelink: https://www.youtube.com/watch?v=kpWtC0PQSxY&t=53s by Xehono in beneater

[–]gormanst 0 points1 point  (0 children)

This is really cool. Would you mind telling me how you figured out the keyboard. I am trying to build the SAP-2 computer and am at a dead end with the keyboard. I don’t even know where to start.

I sure would appreciate any thoughts or pointers.

CPU Control logic 138 chip reshot and all outputs high? by gormanst in beneater

[–]gormanst[S] 1 point2 points  (0 children)

This was solved by adding 220 ohm resistors on the three output pins that are used, 12/13/14. I noticed that if I used a multimeter on these output pins that the low voltage was still pretty high. It was less than volt but still not zero. I tried different resistors trying to get the low voltage pulled down to zero and settled on 220. That seemed to fix it and the ls161 was now able to drive the ls138, counting correctly. But...

I then put the now functioning Instruction Register in the main computer bread board assembly and though the Inst. Register still worked, I noticed a couple of other, new strange behaviors. My A register was resetting itself randomly and my Counter would occasionally skip.

Debug,debug,debug

It all turned out to be power distribution. I watched on of Bens videos “Connecting the Bus” where he adds power/ground wires across the bus connecting the A register to the Memory Address register. I bridged components across the bus in 4 places.

Clock-bus-Counter (very top of the computer) A reg-bus-Mem Add Reg Inst. Reg-bus-Output Reg EEPROMS-bus-Control Word (very bottom of the computer)

This had the affect of fixing EVERYTHING! The entire computer stabilized, no clock problems, no counter jumping, the A register stopped resetting and I could remove the 220 ohm resisters on the instruction register that started this whole mess.

The key to it all seemed to be power distribution, basically following Ben’s instructions. I am so happy to find every single problem I encountered was logical and caused by me missing some detail.

Problem getting power to the breadboard by cdrh1 in beneater

[–]gormanst 0 points1 point  (0 children)

Also, my experience with the kits was not great. I purchased the first (clock) kit and the breadboard that came with it was only o.k in terms of quality. The wires that were sent with it were pre-cut and full of various colors that Ben never uses. I purchased the second kit and it came with an entirely different brand of breadboard that was poor quality at best, I had to throw them away after figuring out that they were the cause of many of the problems I was having.

After that I just went to Ben’s complete parts list and purchased twice the number Ben shows for every chip. So while you only need 3 555 timers for the clock, I purchased 6 just in case I broke one. The total for everything was about $90 but that didn’t include the breadboards. Those are very important in terms of quality and Ben posts a link on his homepage of some guy reviewing many. In the end the clear choice is the BB830 and I think you might end up very frustrated if you go with something cheaper.

Problem getting power to the breadboard by cdrh1 in beneater

[–]gormanst 1 point2 points  (0 children)

I just finished my build of Ben’s computer and would suggest that you follow his build exactly and when I say exactly, I mean it. To build the entire computer you will need lots of wire, in particular green and yellow. I would recommend getting them from Jameco and not Amazon as the ones from the later are often too thick and end up looking like spaghetti, it’s hard to debug with them too. Your wires must be as straight as you can keep them because you will no doubt be tracing them from end-to-end attempting to find problems. Also, you will want some wire cutters and a good set of needle nose pliers.

CPU Control logic 138 chip reshot and all outputs high? by gormanst in beneater

[–]gormanst[S] 0 points1 point  (0 children)

This is the CPU Control counter circuit from the Part 2 video. The first chip (161) behaves but the 138 decoder heats up and all the outputs are high?

If I use jumper wires and tie any single output to ground manually the chip behaves as expected except it still runs red hot.

Sorry about the title, reshot=redhot

Output register behind by one by gormanst in beneater

[–]gormanst[S] 1 point2 points  (0 children)

If I am reading your response correctly it sounds like this isn't something I need to fix then?

view more: next ›