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6502 retro computer

Retro computer utilizing classic MOS6502 microprocessor.

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After buying original MOS6502 microprocessor I decided to use it to build a retro computer.

The classic MOS6502 fascinated me for a long time. In Poland It was never quite popular among the electronics hobbyists in the eighties and the early nineties. Zilog Z80 was much more common in amateur projects back in the days. So I was a little bit intrigued, when I discovered that huge amount of original MOS6502 is available on popular Chinese auction site. Initially I suspected there are probably broken or counterfeit parts, but out of puer curiosity and due to low proce I decoded to order a couple of them, not thinking much about it.

One month later, when I almost forgot about my order, the package containing CPUs finally arrived. I spent few hours building simple test circuit on the breadboard, to check if they are real 6502s. To my pleasant surprise, they were!

So, my another project began. I designed, etched and soldered base PCB containing CPU, clock generator, on power reset circuit, 64kB of RAM (32kB accessible directly and another 32kB visible as four 8kB banks), 16kB of EPROM memory and simple address decoding logic. there is also an address bus buffer (2x 72HCT245) and single output port for LED blinking (74HCT373).

The board is compatible also with parts designed for the Intel bus, I was able to connect it to the 8251 and 8253 chips installed on the breadboard, using them to run EhBASIC. Now I need to design another board with all needed I/O components: UART, GPIO, kayboard and CRT controller, maybe even RTC.

My 6502 retro controller board was in fact an offshoot of this project.

  • 1 × MOS6502AD Connectors and Accessories / Power Connectors
  • 1 × D43256C Memory ICs / Static RAM (SRAM)
  • 1 × M27128 Memory ICs / PROMs, OTP PROMs
  • 1 × 74HCT138 Electronic Components / Misc. Electronic Components
  • 1 × 74HCT139 Electronic Components / Misc. Electronic Components

View all 9 components

  • The I/O board is working now!

    Marek Więcek10/03/2019 at 07:42 0 comments

    Recently I had some free time to work on I/O board for my 6502 computer. It is complete now. I consists R65C51P2 UART controller, 8242 AT keyboard controller, MC6840 timer, M6245B RTC and 8255 GPIO chip (some of its pins are wired to form Commodore IEC port). Project also provides possibility of using CF card, but connector has not been soldered yet.

    At this point the computer works. It uses serial terminal and EhBasic. Now I need to add routines to support other peripherals.

    What's next? CRT controller, probably with TMS9929A chip.

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Dave's Dev Lab wrote 02/06/2019 at 21:31 point

nice looking design! any schematics available?

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Dan Maloney wrote 02/04/2019 at 21:26 point

Sometimes you get lucky with China orders, sometimes you don't. I'm still waiting for a batch of piezo sensors I ordered before Christmas. Glad you got the chips, and that they turned out to be legit.

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Alexander wrote 02/04/2019 at 19:06 point

Very cool! If you like the 6502, check out the 6809. It was even lesser-known than either the 6502 or the Z80, and it has some really unique features and quirks that make it fun to work with. Cheers, and awesome work! I love the homebrew etching, it matches homebrew computers perfectly (:

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