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IC date codes

Overview

IC date codes help to date keyboards. In most cases, finding manufacturer details on IC date codes is difficult or impossible, as they have changed practices and old ICs do not follow their modern marking practice.

The examples detailed on this page are not all confirmed; some assumptions are made based on the correspondence of unconfirmed codes against clearer date codes of chips from other manufacturers or plants, and with verified manufacture dates.

The diagrams are based on real ICs, but are simply examples, as presentation varies by size, shape and age of the IC and likely also by plant.

Terms

The following terms are used:

Y
One-character year (typically 0–9, repeating each decade)
YY
Two-digit year (00–99)
M
One-character month
W
Week of month (1–6?)
WW
Week of year (01–52)

Date code identification

When looking at an IC, there may be multiple codes present. These include model numbers, lot numbers, date codes, and other information. Because date codes are often anywhere from two to four characters, and either numeric or alphanumeric, it may not be obvious which code, or which part of which code, indicates the date of manufacture. In the case of Intel chips, the date code can be buried cryptically inside a much longer code.

Ignoring prefix and suffix letters, start by looking for any four-digit numeric codes where the first two digits are a plausible year of manufacture (typically up to two or even three years before the product was assembled). For example, a code of “8049” in a 1985 product is unlikely to be a date; in this case, 8049 is the model number (Intel MCS-48 family microcontroller). Failing this, try for three-digit codes, where the first digit is a possible year. In either situation, the last two digits should not exceed 52 (the number of weeks in a year).

Common formats

YYWW

By far the most common format is YYWW: two digit year followed by two digit year. These digits are frequently followed by (and also preceded by) additional letters; in the images below, examples include “+B9106” (leading “+B”) and “9031KE” (trailing “KE”). YYWW dates are the easiest to spot, as the year is readily recognisable.

“9106”: 6th week of 1991 (Mitsumi-made Apple Keyboard II)
“9122”: 22nd week of 1991 (Datacomp DFK-192)
Neve Necam 96 keyboard with ICs dated to 1984, which is also the design date on the PCB
NTC KB-6251 keyboard controller with various four-digit codes, and the date code highlighted: “9031” for 31st week in 1990

However, there are also particular occurrences of ICs where such a code is present that is not a date, or not a relevant date. In many cases, these codes can be readily ruled out. For example, the National Semiconductor INS8048 chip above has the sequences “0810” (suggesting 2008) and “8048” (suggesting 1980), which can be discounted on the basis that an Apple Keyboard II could not have been made around either of those dates. Further, “8048” and “8049” indicate models within Intel’s MCS-48 microcontroller family, widely used as keyboard controllers. MCS-48 models were second-sourced to a variety of companies including National Semiconductor (the INS8048 pictured above) and Signetics (the SCN8049H pictured above), so those numbers will appear on many keyboard controllers.

YWW

Another common format is YWW: a single digit year. While this is often indicated as a way to save space, it is also often used where there is plenty of room for a two-digit year.

GoldStar

GoldStar used at least two formats. YYWW is more common; the other format is yet to be understood.

YYWW

Examples

HFO

VEB HFO (Halbleiterfabrik Frankfurt (Oder)) used standard East German IC markings.

YM

Year is a single letter, and is one of the following (per Kodiertes Herstellungsdatum auf elektronischen Bauelementen, “Manufacturing date codes of electronic components”):

Letter 1970s 1980s 1990s
A 1990
B 1991
C 1992
D 1993
E 1994
F 1975 1995
H 1976 1996
I, J 1977 1997
K 1978 1998
L 1979
M 1980
N 1981
P 1982
R 1983
S 1984
T 1985
U 1986
V 1987
W 1988
X 1989

This seems to be an application of West German date codes.

Month is a single character, and is one of the following:

Character Month
1 January
2 February
3 March
4 April
5 May
6 June
7 July
8 August
9 September
O October
N November
D December

Examples

Hitachi

YMW

The following details were obtained from a website. The format is YMW: a single-digit year, followed by a single-digit month (A–M, with I excluded for clarity, to avoid confusion with 1) and finally the week number within the month:

The months are as follows:

Letter Month
A January
B February
C March
D April
E May
F June
G July
H August
J September
K October
L November
M December

Examples

Intel

YWW

According to John Culver at the CPU Shack, Intel’s format ca. the 1980s was as follows:

AYWWLLLL

The individual positions denote:

A
Assembly location
Y
Single-digit year
WW
Week
LLLL
Lot number

Examples

YYWW

Intel also used YYWW. According to George Phillips Jr’s Collector’s Guide to Vintage Intel Microchips, Intel introduced date codes around 1973, and wrote these on the bottom of the chip. These are reported to be in YYWW format.

Codes on ICs like “P3476”, “8B290”, “43A22”, “082A0” and “0216F” (four digits and one letter in any order) are not date codes. Instead, these are lot numbers, with the date present on the bottom of the chip if at all. In some cases, there are two such codes on a chip; the other is typically one letter then four digits; these are also not date codes.

The YYWW format can also be used on the top of chips. In some cases, chips also have a four-digit code at the top right. The top-right number is the “ROM code”, which according to John is is assigned sequentially per family. Although these ROM codes resemble dates, and seeing one with a “month” above 52 is rare, they are not date codes. The diagram below shows a keyboard controller with both a YYWW date code as well as a ROM code — this seems to be a 90s design:

Examples

Ortek YY

Intel-manufactured Ortek keyboard controllers have a confusing property that the usual Intel … thing with the date code and lot number … is replaced with the word “ORTEK” followed by a two-digit year, for example:

P8049AH 8731
ORTEK 91
101SX-4
INTELⓂ©1977

These ICs are not known to have a manufacture date. John figured that the year given in the ORTEK line would be the copyright year of the Ortek software written into the ROM. As such, the only guarantee from an Ortek controller is that the ROM is at least as old as the year written on it!

Examples

Mitsubishi

YWW

The official formats for Mitsubishi IC lot numbers are (per a 2008 archived document):

YWWRRR
YWWR

The individual positions denote:

Y
Single-digit year
WW
Week
R
One-digit running number (shorter codes)
RRR
Three-digit running number

YYWW

Inspection of 80s ICs shows that the lot number clearly begins YYWW, with two additional digits that are often 00. This suggests:

YYWWRR

This format is not corroborated. It appears that decoding the date portion involves determining whether the first two digits represents a meaningful year, especially in relation to the approximate age of the equipment in question.

Examples

Newtech

YMW

Newtech ICs seem to be rare. It would appear that the date codes on these are identical in format to Hitachi YMW; the example given would be dated by Hitachi coding to the first week of March in 1990, which fits in with the roughly February and April 1990 dates on the GoldStar chips found on the same keyboard.

Examples

Texas Instruments

YYWW

Texas Instruments markings appear to vary. The following format is highly likely to be YYWW, which is a format that TI apparently no longer use:

Examples

YWW

Texas Instruments also used a three-digit format, with a single digit year. The remaining digits appear to be the week, based on correlation with ICs from other brands with similar week numbers.

Examples