I ordered a bunch(2) bet goodies from Michael Hill at bitfixer.com; a PETdisk MAX and a ROMulator. The former is a floppy drive emulator that plugs into the PET's IEEE-488 port, the latter is a RAM/ROM replacement daughterboard that plugs in between the motherboard and the 6502.
When I got my PET 4016-N, I immediately knew I had to upgrade my RAM to 32k and have some form of disk drive. The thing is, Commodore punched holes through where the 8 extra 4116 SRAM chips would go on the mo
The Compaq Portable II is a really weird computer. I've found a few blog entries and videos that are supposed to explain how this is supposed to work but none seem that helpful. So I decided it'd be nice to make a complete how-to for people that can't figure out how to get their Compaqs working(like me a week ago). All disk images required can be found at the bottom.
Before I begin, a huge thanks to @wierd_w for helping me get the Compaq working and sending me the diskettes nd variou
I watched through most of Ben Eater's 6502 computer video series a while back (if you haven't yet I really recommend you go watch them; I really learned a lot). He uses a 65C02, a 65C22, a 62256, 28C256, and aather crude address decoding to make everything tick. I didn't watch all the way through the video series, but I don't think he made the system to be programmable without using the EEPROM and an external system. So, I thought it would be rather cool if I could make what was essentially the
This was originally planned to be a status update but evidently became too long to be one. So here goes:
I’m not a fan of Ernest Cline. I loved Ready Player One, and I’ve probably read it over 50 times. Armada was fun too, but much less so than RP1 because half the book is “borrowed” from similar books including RP1, so much so that one could argue it is more plagiarism than homage.
I didn’t even know RP2 came out until like 15 minutes ago, and from what I can gather it’s a
I had a theoretically working computer by the end of the last entry. It could input and output binary data to and from RAM, ROM, a 65C22, and some LEDs. I was heavily considering a form of video output and keyboard input, and settled on using the Motorola MC6847 for the former, and was undecided about the latter. I decided to think of a list of things I wanted to add onto the computer (from most to least important), and here it is:
PS/2 Keyboard
Another 65C22
Some sort of s
Remember how I made that PS/2 keyboard interface? Yeah, I decided to get rid of it. Too complex on the software side. Now I have this 8x8 keyboard matrix. It has every key I thought I might need for the computer.
I know the drawing of the matrix is messy, but who cares. This is how the matrix works: the computer outputs a 1 to all 8 PA bits upon initialization. The other side of the switch matrix is ORed to CB1. If any key is pressed, CB1 will go high and trigger an interrupt. The co
I'm terrible at 6502 programming. Thankfully, programming a simple BIOS can be done by only using simple commands like LDA, JSR, TXA, etc. I wrote a simple program that set up all the ICs such as the 65C22 and MC6847 to whatever mode I wanted them to be in apart from the YM3812, since I've yet to figure out how to program it. I also made a "video counter" to keep track of at what memory location the previous character was placed. This acts as the cursor. Also, the I don't think the MC6847's data
Like I mentioned in the status update, I was attempting to port WozMon to my 6502 computer, until I remembered something; I hadn't written a proper keyboard decoding routine! Well, this was mainly because I had no idea how to program something like this, and was trying to test every bit of the matrix manually to decode the key presses. That was obviously much too inefficient, and it didn't even work because there were so many lines of code, resulting in out of range branches. Not good.
So, it's been, what, four months, since I last posted an entry on the 6502 computer? I've been slacking off, doing Blender and Lua stuff in the meantime. Then I got bored and decided to work on the computer a bit.
The progress so far. To oversimplify things, I'd made everything that makes the computer... a computer. The CPU, I/O, RAM, ROM, video chip, and address decoding. I'd only planned on the sound, UART, IDE, and floppy interface, without making much progress due to them being c
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