Project 816 at a glance, as its specification describes it. Nothing is built yet: these are planned values, and some remain to be defined.
Processor
Processor
WDC W65C816S, 16-bit, in native mode, at 3.3 V
Speed
8 MHz at most (the processor’s maximum at 3.3 V); effective speed estimated at 4 MHz for isolated accesses and up to 8 MHz for sequential reads; average estimated at about 6 MHz on a real program (100 MHz QSPI link), to be measured
System controller
Gowin GW1NR-9 FPGA soldered on the board (“the 9K”), 8,640 LUTs
ROM
None. All the memory is RAM. At start-up, the processor is held in reset and off the bus while the
9K writes into PSRAM the boot code supplied by the Pico; the 65816 vectors are part of what is loaded.
The proposed mechanism goes through a memory port of the 9K (see the
register map); it is still to be validated.
RAM
Main memory
16 MB of PSRAM: two 8 MB APS6404L, over QSPI, connected to the 9K alone
65816 address space
16 MB (256 banks of 64 KB), entirely RAM
Input/output
four 256-byte pages at $00:9C00 – $00:9FFF, 32 registers per block
Video memory
in the Tang Nano 20K’s SDRAM, outside the processor’s 16 MB; usable size to be defined
Display
Device
Tang Nano 20K, a VERA-like video chip (the one in the Commander X16)
Output
HDMI
Access
indirect, through two auto-incrementing ports within 32 registers at $00:9D00, as on the VERA
Resolution, modes, colours
to be defined: neither the specification nor the register map (v0.1) fixes them yet; a VMODE register will select the mode
Sound
Synthesis
in the 9K: free jt51 (YM2151, FM) and/or jt49 (AY-3-8910) cores; final timbre to be decided (FM, SID or POKEY)
Samples
one PCM channel with a FIFO
Codec
TLV320AIC3254 (fallback: SGTL5000), at 1.8 V, controlled by the 9K: line out, line in, microphone in, front-panel HD Audio
Recording
by DMA, lighter 8-bit mono modes at 11 or 22 kHz
Storage and input/output
Storage
microSD, FAT file system handled by the Pico 2 W
USB
7-port hub (5 at the rear, 2 at the front), Full Speed, 500 mA per port
Network
the Pico 2 W’s Wi-Fi
Clock
DS3231 with a CR2032 battery
Joysticks
double DE-9 (Atari and Sega wiring)
Expansion
2 × 25 header, buffered data
Form factor
Board
Mini-ITX, 170 × 170 mm, 4 layers (Phase 2)
Power
ATX or picoPSU, 3.3 V and 5 V only
Budget
€250 to 450 for the complete machine, case and power supply included
Sources in the repository : docs/SPEC.md, docs/choix-controleur-systeme.md.