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

The chips in NES/Famicom units vary in package styles a lot. This section tries to identify possible manufacturers of the chipset with cross-references. Please note this section is currently a work in progress and info may change.

If you have any suggestions, ideas, info, etc; Please leave them on my user talk page.

Chip	Image	Reference	Possible Manufacturer	Country of Manufacture	Comment
RP2C02C			Hitachi	Japan	Supposedly identical bottomside imprint format as other Hitachi-made chips, such as some YM2149F. Pin 1 marking and font are near-identical.
RP2C33-01A			Hitachi	Japan	Shares package style with V9938 VDP, and Ricoh 2A10.
RP2A03G			Unknown Manufacturer	Hong Kong	Shares font and package style with MOS 6510 CPU, from one decade prior. Visually similar MOS 6510s are marked with "HONG KONG" on the bottom.