iz8dwf | Making a MOS7501/8501 replacement adapter with a 6502 (Plus C16 upgrades). Part 2. @iz8dwf | Uploaded April 2023 | Updated October 2024, 1 hour ago.
This is my second (and I'd say successful) attempt at making a "socket add-on" to use the more commonly available 6502 in place of the 7501/8501.
The first attempt showed some flaws that I try to correct with a second revision. The adapter uses two 5V supply, 32-cells CPLDs.

Many thanks to Gerrit Heitsch for providing scope captures of real 8501 signals and discussing the implementation details of these CPUs.

First part video:
youtube.com/watch?v=z5Evpt0pU9s

6510 to 7501/8501 adapter and kernel hack:
hackjunk.com/2017/06/23/commodore-16-plus-4-8501-to-6510-cpu-conversion

TED architecture documents:
zimmers.net/anonftp/pub/cbm/schematics/computers/plus4/264_Hardware_Spec.pdf
zimmers.net/anonftp/pub/cbm/schematics/computers/plus4/264_Hardware_Spec_DocE.jpg

MOS 7501 preliminary datasheet:
zimmers.net/anonftp/pub/cbm/documents/chipdata/7501/index.html

MOS 6510 datasheet:
archive.6502.org/datasheets/mos_6510_mpu.pdf

MOS 6502 datasheet:
archive.6502.org/datasheets/mos_6500_mpu_nov_1985.pdf

Atmel/Microchip PLD design resources:
microchip.com/design-centers/fpgas-and-plds/splds-cplds/pld-design-resources

DLC5 III parallel JTAG cable schematic:
http://dev.ivanov.eu/index.php?page=dlc5-jtag

UrJTAG for Linux:
urjtag.org

Timeline:
00:00 - Welcome
01:01 - First adapter was not good
02:37 - C16 upgrade to 64k
05:16 - C16 5V regulator upgrade
11:01 - CPU adapter design fixes
14:10 - New adapter's PCB
17:12 - Testing on the C16
23:49 - Other adapters?
25:09 - Running a plus4 demo