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

Official Famicom and NES systems often have different 7400 logic manufacturers used between boards.

• Sharp (LR74xx; LR74xx chips are used almost exclusively for HVC-CPU-05 consoles?)
• Hitachi (HD74xx)
• Texas Instruments (SN74xx)
• Fujitsu
• Fairchild (Exclusively used in HVC-CPU-03 boards?)

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.

Hardware Observations

Weird things with hardware I might not be able explain, or understand. It's all documented here, per request of "org" due to it otherwise being lost to time on a discord channel.

Mapper 106 Behavior

INES Mapper 106, or at least my copy of this cartridge, works on nearly all revisions of CPU and PPU I can test with but RP2C02B. I don't know the full extent of why this happens. But it's my own theory that it is possibly either due to a change in CPU manufacturer leading to a slight behavioral difference, or the different PPU.

Observations listed below: (Note: "Chip Manufacturer" lists the company when possible. Otherwise, it lists the origin country usually marked on the package, which may have variations.)

Table of Results

PCB (eg: HVC-CPU-02)	CPU (with Chip Manufacturer)	PPU (with Chip Manufacturer)	Status	Notes
HVC-CPU-03	RP2A03 (Hitachi)	RP2C02A (Hitachi)	Works fine.	No issues.
HVC-CPU-05	RP2A03 (Hitachi)	RP2C02C (Hitachi)	Works fine.	No issues.
HVC-CPU-05	RP2A03 (Korea Mfg. #1)	RP2C02B (Hitachi)	Crashes after some time. Game effects include halting with all background tiles vanishing (sprites are untouched, and remain uncorrupted), with the IRQ misbehaving, drawing a weird pattern of IRQs down the screen. The game seems to mostly lock up, but is still running extremely slowly. This continues for approximately 5 minutes until the game fully crashes.	PPU known to exhibit weird behavior supposedly not present on other 2C02B PPUs. Otherwise acts (mostly) the same as a normal 2C02B.
HVC-CPU-07	RP2A03E (Korea Mfg. #2)	RP2C02E-0 (Korea Mfg. #1)	Works fine.	No Issues.
HVC-CPU-07	RP2A03G (Korea Mfg. #1)	RP2C02G (Korea Mfg. #1)	Works fine.	No Issues.
HVC-CPU-07	RP2A03G (Hong Kong)	RP2C02G-0 (Hong Kong)	Works fine.	No Issues. Functionally identical results to G-revision CPU/PPU.
HVC-CPU-07	TA-03N	TA-02N	Works fine.	No Issues. Functionally identical results to G-revision CPU/PPU.
HVC-CPU-07	UA6527P	UA6528	Works fine.	PAL clone CPU in NTSC system, with NTSC PPU. No Issues. Results would likely be somewhat close to E-revision CPU/PPU.
HVC-CPU-07	2011	2010	Works fine.	No Issues. Functionally identical results to G-revision CPU/PPU.
?? (MicroNewton PCB)	XYZ-6783	WDL 6528	Works fine.	No Issues. Functionally identical results to G-revision CPU/PPU.
?? (DarYar PCB)	"6538N"	"6528"	Works fine.	No Issues. Functionally identical results to E-revision CPU/PPU.

Things to note:

• Korea manufacturers are determined by the bottom package eject holes either printing "KOREA" on the bottom, or as part of a "stamp" embossed onto one of the bottom eject holes.
• All HVC-CPU-07 tests were done with the same PCB, as it is socketed.
• PAL 6527P with NTSC 6528 is mostly similar to an NTSC Famicom system with E-revision (or compatible) chipset. Major difference is CPU speed, and APU generated frequencies.
• Despite being an earlier revision, the 2C02B board and its chipset were made after the 2C02C's board and chipset.
• The RP2C02B PCB is the only PCB I own containing a Korea-manufactured 2A03.

Testing Method

The bug was originally found during a casual playthrough of the cartridge (Which contained Super Mario Bros. 3). When I originally discovered the game crashed after a set time, I tried to beat the game as fast as possible, to try and beat it before it crashed. All test runs from this point on use the "Double Warp Whistle" trick, as a result.

Possible Cause

• According to org, "This happens when NMI is executed more than once per frame or its execution diverges from VBlank. This can be caused either by an IRQ from the timer, an IRQ from the cartridge, or an incorrect CPU/PPU timing alignment."

Todo

• Check cartridge IRQ and PPU /INT lines of the "faulty" unit with a logic analyzer, and cross compare to a working console.