• The W-2K

    Buzz Pendarvis07/24/2020 at 21:16 0 comments

    All of the following was done months ago, but i forgot to upload anything on it.

    Recently I created a version of the breadboard computer i made on a perfboard. Because of the amount of RAM, I decided to name it the W-2K. Right now, the only form of IO that it has is a board with decode logic for a character LCD, though i planned for a PIO on the same board to drive a keyboard. I dont really like using character LCDs as they have microcontrollers on them, but in this case it was the easiest way to just get something working. Below are a few videos of different tests i performed as i was developing the machine.

    As for the text LCD, i never got a video because the whole process was really just pressing the reset button and seeing the text on a screen, so all I have is this very very low resolution image:

    (At the bottom you can see where the PIO would have gone)

    Since the creation of this computer, I've made a lot of progress with the W-32 itself. I ordered, received, and assembled one main board (having  just RAM, ROM, the clock and the CPU), though I found a few problems and have ordered a revised version. With the new CPU boards, I've also ordered a keyboard interface board that uses a PIO to read from a keyboard matrix i ripped out of a broken TI-99/4A. Though that board is untested, I'm hoping it will work. 

    Here is an image of the completely assembled (not working) W-32 board without the clock or ROM put in their sockets:

    That's all for now. I'll be getting my new boards some time around Wednesday of next week, so expect another update in a week or so.

  • Updates

    Buzz Pendarvis02/02/2020 at 07:14 0 comments

        Sorry for the long break, I've been really busy with school recently, and haven't worked much on the project. I've decided to make changes to what my current goals are, although I plan on improving on/modifying the computer when I have more time.

        The biggest change is that it will no longer be the W-64. To speed up the design process, I'm getting rid of the memory banking idea for now. I may still include some circuitry on the main board that will make memory banking possible later, but for now it will have to be the W-32. It will only have 32KB of RAM and 32KB of ROM (might make this 16KB of built in ROM and 16KB of cartridge space. Not sure yet). 

        I'm going to put a connector (or a few) on the board so that I can add video, disk, more memory, or whatever else later when I have more time. Because I wont have any real I/O when i'm done with the main board, I'm going to put an 8 bit data latch with some LEDs on the main board for testing purposes.

        That's all for now. I'll be able to work on the computer on Saturdays every week, but not a lot other than that. I can't wait to get the computer working and start writing programs for it, but for now, I'll start redesigning the computer and making sure I have everything i need. Thanks for reading!

  • Prototype on breadboard

    Buzz Pendarvis11/13/2019 at 06:28 0 comments

    I constructed a prototype on a breadboard just to learn about how the CPU works. It has an 8 bit input, an 8 bit output, 2K ROM and 2K RAM. I wrote a test program that takes two inputs and adds them together.

    Here is the YouTube video.

    in the video I add 3 and 1, and it outputs 4.
    the clock is very slow, only a few Hz. not sure exactly how fast it is.