Golden Delicious

This project started as a portable Apple ][ by using the Mega-II chip from an IIGS. (This chip is precursor, and slightly different to the Gemini in the Mac LC compatibility card.) However, it evolved into making a miniture Apple IIe compatible computer.

This repo contains the KiCad design files, RP2040 firmware, and notes for the Mega IIe computer.

Rev 3 Video

This element14 Presents video documents the effort to get from an Applesoft Prompt to a fully functional computer, in a miniature case.

https://www.youtube.com/watch?v=gFCD4s_hsb4

You can find additional information on the element14 Community or in this Hackster.io article.

Bit Preserve

This project is why I started Bit Preserve, a project to archive vintage computer schematics.

Notes

When live streaming the probject, I kept some notes here for future reference.

(Off-)Stream Notes 2021-10-02

• Attempting to book the GD with a IIc ROM results in a lock-up.
  • graphics get initialized and the memory is dumped to the screen, but no beep and nothing past that.
  • Logic Analyzer suggests BASICINIT is doing a monitor version check in the F8 ROM, but failing. It calls a jump called HANG. Even though the 6502 should be jumping in a circle, it seems to keep doing other stuff. (Maybe it is just bus fetches that do nothing?)
• SLOTMAKER Bus Headers on the IO board are pinned out different from the SLOTMAKER Bus Header on the MEGA-65c02. For a ribbon cable, each pin-pair needs to be swapped, except for the last two. They are GND.

Stream Notes 2021-10-01

Golden Delicious Rev 2 booted! Yay!

• ~DMA is wrong level

  • The two `245 buffers have their enable pins connnected to ~DMA. I made the mistake of thinking that MEGA drove the ~DMA signal. That is not the case, nor does it make sense after thinking about it. For now, the `245s have pin 19 lifted and tied to ground to always enable them.
  • When connecting the IWM or a card to slotmaker, ~DMA situation needs to be resolved.

• IIe / 6502 decoder for Waveforms / Digitial Discovery has been updated.

• This forum post has Digilent Waveforms beta builds that are downloadable without filling out the annoying registration form. (Or just use asdf for all of the fields.)

Stream Notes 2021-06-02

• Wherefore no IIe ROM in the IIgs? Is it in the MEGA-II?
• Warphammer: this seciton looks rommy
• rjhelms: that's the big question mark - there could be logic in the Mega II that never actually gets used because the CYA is doing it all in this implementation
• al: keep it all breakouts
• can we decode ROMEN1 and ROMEN2 ourselves?

Stream Notes 2021-05-19

Things to look at on the scope:

• Composite signal out of the Mega II
• What is Mono-Color from VGC doing to Chroma into MC1377
• Is VGC refreshing apple II DRAM (or is it the Mega)
• why is the 28 MHz oscillator enabled/disabled from the VGC's !SYNC pin?
• PLCC Pinout Page

Renesas / IDT OSC: XLH735028.636360I

• XL H 7 3 5 0 28.636360 I
  • XL = 1,000,000 af
  • H = LVCMOS En/Dis Pin 1
  • 7 = 7.0 x 5.0 mm
  • 3 = 3.3 VDC
  • 5 = 100ppm for -40C to 105C only on tuesdays when the moon is full and it hasn't rained for a few days. also if you ate green skittles recently Note1

BoM for Protoboards

• Possible MC1377 Source

Stream Notes 2021-05-16

• WDC Application note on using 65C02 in Apple II and other old systems
• 65C02 Datasheet