User:Forple
I'm documenting small bits of info and data that doesn't really warrant its own page.
Ricoh Chip Date Format (Pre-1990 approximate)
Please note that this format has been primarily tested with the following ASICs:
- Ricoh 2A03 CPU (RP2A03x series) CPU for Famicom/NES
- Ricoh 2C0x PPU (Rx2C02x series) PPU for Famicom/NES
- Ricoh 2A10 SOC (RP2A10x series) SOC for Atari 2600 "Unicorn" models
- Ricoh 65C02 CPU (RP65C02x series) CPU second-source of 65C02
It may work on other chips produced by Ricoh, but this cannot be guaranteed.
This date format documentation is possible in no small part from Fiskbit.
Format
2A0x: YMW ?? 2A1x: !! YMW ?? Y = Year M = Month W = Week ?? = Unknown !! = Unknown (present on the 2A10, always set to "38")
Year is a single digit 0 through 9. When 1990 rolled around, they seemed to just wrap back over to 0 and count back up, while
changing the format a bit (see below).
Month is represented with a letter, from A to M. Likely for readability reasons, letter I is omitted due to visual similarity
to the 1 digit.
Week is a digit, 0 through 9, much like Year.
The "Unknown" fields serve a purpose not yet understood.
For some reason, Week was updated in 1990 to include letters. It's not entirely known why.
- Month Table
- A = January
- B = February
- C = March
- D = April
- E = May
- F = June
- G = July
- H = August
- J = September
- K = October
- L = November
- M = December
Example dates (decoded)
- Chip: RP2A03
- Original: 4C3 27
- Decoded: March 1984, Week 3 (March 11 - March 17)
- Chip: RP65C02
- Original: 4J2 16
- Decoded: September 1984, Week 2 (September 2 - September 8)
- Chip: RP2C02B
- Original: 4D2 89
- Decoded: April 1984, Week 2 (April 8 - April 14)
- Chip: RP2C02C
- Original: 4B4 85
- Decoded: February 1984, Week 4 (February 19 - February 25)
- Chip: RP2A10
- Original: 38 7K3 10
- Decoded: October 1987, Week 3 (October 11 - October 17)
- Chip: RP2A10
- Original: 38 8L1 54
- Decoded: November 1988, Week 1 (November 1 - November 5)
Observed Logic Chip Manufacturers
- Sharp (LR74xx; Seems to be used almost exclusively for HVC consoles?)
- Hitachi
- Texas Instruments (SN74xx)
- Fujitsu
There may be more, feel free to edit this section if you find others!
Ricoh Package Types
TBA
