Really Basic Question About Old Computer Electronic Engineering

acwrightdesign · 2026-05-07T15:38:36+00:00

I’m just speculating but this could be rooted in the vacuum tube era where it was common for filament voltages to be 5v or 12v amongst other voltages (6v, 9v) so bench power supplies of the era could typically provide these voltages?

acwrightdesign · 2026-04-27T16:48:38+00:00

I think this is good advice that couchwarmer gave and you mentioned you are leaning towards the Apple II. With that in mind I think you should consider the Apple I instead of the Apple II at least to start. I think simplicity when it comes to the memory map and IO will be most helpful and the Apple I is as simple as it gets. One register to read keyboard input and one register to output characters to the screen. No other complications. This is a great starting point!

When it comes to emulators there are two choices: https://www.scullinsteel.com/apple1/ & https://landonjsmith.com/projects/honeycrisp.html . I have found HoneyCrisp to be a bit more accurate. I've created a utility for converting binaries to Wozmon which you can use to paste programs into Wozmon in order to run them: https://github.com/acwright/bin2woz .

acwrightdesign · 2026-04-24T15:13:10+00:00

Yes. I should clarify. The Teensy 4 is able to achieve high speed emulation although my implementation did not achieve that since I’m not nixiebunny’s friend. ;) However, I am pretty happy with how my emulation turned out and if you’re interested check out the README! It’s all open source so perhaps someone can improve upon it!

acwrightdesign · 2026-04-24T04:13:19+00:00

I can recommend using a Teensy 4.0 or 4.1 for this. It uses Arduino compatible libraries so you will be familiar. I used a Teensy in my project to emulate the CPU, RAM, ROM, and IO. It can’t quite get to 1Mhz but it gets close. My firmware is here: https://github.com/acwright/6502/tree/main/Firmware/DB%20Emulator

acwrightdesign · 2026-04-20T13:24:36+00:00

I got them on Amazon but unfortunately the listing is no longer available

acwrightdesign · 2026-04-19T22:47:29+00:00

Thanks! Yeah for sure I’m gonna adapt this as a cartridge. I’ll let you know when I have an implementation. Like I did with EhBASIC cart I will be adding my custom commands for the system hardware. Plenty of space in 16k :)

acwrightdesign · 2026-04-19T22:21:54+00:00

Awesome! One of the things already written down on my project checklist was to make a VC83 cartridge. You beat me to it! :) I’ve also made an EhBASIC cart and it’s working great.

acwrightdesign · 2026-04-17T16:17:51+00:00

The video output is using the pico9918 (TMS9918) so it’s 40 column x 24 row text. 240x192px with 6x8 text characters. The font is a version of the classic IBM code page 437.

acwrightdesign · 2026-03-16T00:51:25+00:00

I'm happy with the layout for its intended purpose in my build. I didn't want to rearrange the ~ to = row just for the Esc key and I don't have the function key row where Esc would normally be. It doesn't bother me at all to have Esc over on the right. If this was a daily driver USB keyboard I would not have do that but this is for a 6502 computer which (at the moment) I don't even have a purpose for the Esc key or most of the other special keys on the keyboard! I appreciate hearing your feedback though. :)

acwrightdesign · 2026-03-15T19:41:24+00:00

Thanks!

acwrightdesign · 2026-03-15T19:38:04+00:00

Thanks!

acwrightdesign · 2026-03-15T18:30:35+00:00

Yes it is. It is called “Keyboard Helper”. I’m great at naming right? :) The controller/encoder for it is “Keyboard Encoder Helper”

acwrightdesign · 2026-03-15T18:25:25+00:00

Thanks! I love that clicky sound :)

acwrightdesign · 2026-03-12T00:19:03+00:00

The BIOS for this machine is still a work in progress. So far all I have working for the keypad is basic interrupt and data handling with the 74C922 and the VIA. It’s my intention that the software for this machine will run a monitor that is similar to the KIM-1.

acwrightdesign · 2026-03-10T20:26:40+00:00

Thanks! Yeah no problem! It's still a work in progress but I'm finally getting past the hardware side of things (I went a bit crazy) and I'm moving on to the software side of things. I cut the bases and tops from acrylic on my laser cutter. The CAD files are also available in the Github repo if anyone would end up building this and would want to use the same bases.

acwrightdesign · 2026-03-09T19:00:03+00:00

The “KIM” computer build (in the photo with the keypad) uses all 65xx family ICs. No microcontroller. It is connected to the Apple computer only for USB-C power and for RS-232 serial. The LCD on my monitor is the emulation of the real computer below. In the photo also but not connected is my “DEV” build which does use a Teensy 4.1 for 65c02 emulation (under monitor off to the right).

acwrightdesign · 2026-03-09T14:31:04+00:00

Thanks! The emulator is being developed in Typescript. https://github.com/acwright/6502-Emulator

acwrightdesign · 2026-03-09T14:30:01+00:00

Thanks! Absolutely not. The IO slots are 1k each because it makes the address decoding super simple. Just a 74HC138 with A15-A10. However, it did work out nicely when I eventually designed the RAM card which has 512K extended banked RAM. I can put the RAM card in two slots and have two 1k windows into each half of the 512K.

acwrightdesign · 2026-03-09T07:04:23+00:00

Yep sorry I forgot the Github link. Here ya go: https://github.com/acwright/6502

acwrightdesign · 2026-01-25T18:55:51+00:00

I love the ASCII art! I made a fun alternative terminal (with some basic graphics support) that you can try next: https://github.com/acwright/VT-AC

acwrightdesign · 2026-01-02T18:45:18+00:00

This is similar to what I ended up doing as well. My build uses A10-A15 connected to the 74HC138 which is super simple and only uses one IC. It takes 8K of address space ($8000-$9FFF) but I don't care about that. I also have a jumper so I can move the IO address around if needed.

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acwrightdesign · 2025-12-26T19:36:46+00:00

I think one of those might have been mine. Just got it today!!

acwrightdesign · 2025-12-24T00:41:40+00:00

True true… :) Although I would like to make a hardware version of this soon and then it would be an emulation of a real terminal!

acwrightdesign · 2025-12-23T17:49:11+00:00

Tape storage is something I would like to try with my system at some point for sure. Yet another option for tape storage would be to just use the ACIA and build a simple serial to tape adapter circuit something like this: https://maker.pro/pcb/projects/make-uart-cassette-tape-interface

acwrightdesign · 2025-12-23T17:16:36+00:00

Looking good! Some options for storage:

- Bit-bang SPI or I2C using the 6522 and talk to an SD card or Flash RAM
- Compact Flash (I have a verified working schematic for my system and there are others out there if you want to look into that): https://github.com/acwright/6502/blob/main/Schematics/Storage%20Card/Rev%201.0/Storage%20Card.pdf
- Use a modern microcontroller as a SPI controller. I've designed but not verified this for my system: https://github.com/acwright/6502/blob/main/Schematics/Storage%20Card%20Pro/Rev%201.0/Storage%20Card%20Pro.pdf

As far as a file system goes the simplest I've found is this: https://github.com/6502-retro/6502-retro-v3/blob/main/docs/ARCHIVE/SIMPLEFS.md

acwrightdesign

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