I did add a 3.8V LDO, internal 3.3V would be free but I like to get to 75% of 5V as high.
6x PLL from dotclock so will always be in phase for your cycle-counting 8bit c8051 code.
Every single expansion port pin is hocked up to a gpio.
Can fit seven 8KB carts images.
USB bootloader lets you swap in and out cart images.
Can also be programmed from the C64, as it will work as a 64KB REU,
but as it's flash, you should write-once-read-many.
Emulate a math-coprocessor as it does 12MHz multiplication
and 6MHz divisions (something that was available in 1980's)
Makes for a great dead-test cart.
No buttons, it checks nmi (restore key) so hit it twice within 1sec etc.
It then reads keyboard to see what other key you hold down.
You Tri-state in software, so some care is needed before/after MOVX.
In theory you could move data at 3MHz while Phi2 is high but C64's DRAM is 160ns, so 1MHz it is.
Only sticks out 12mm as usb is snug against c64 case
![Image](https://i.postimg.cc/hGWx8Wkc/2022-01-11-1.png)
What pad goes to what pin AFTER i put the must be routed traces, could not be done on a 2layer board otherwise.
![Image](https://i.postimg.cc/06NrNfb2/2022-01-11-2.png)
I ordered 4 boards ($7.50 each shipped) with digikey DK Red service, So Feb I will send carts to 3 top co-code helpers.