American seller
eBay member for over 20 years.

• NEW, RECENTLY MANUFACTURED.
• 2321 date code = year 2023, week 21 = May 2023 .
• These Dallas chips are the most recent factory production and have never been installed — the internal lithium batteries will not be initiated until you install them in a motherboard.
  • Factory: "When the DS12887A and DS12C887A are shipped from the factory, the internal oscillator is turned off. This prevents the lithium energy cell from being used until the device is installed in a system."
• You can comfortably expect these chips to run 10-15 years, maybe longer.
• Replaces Dallas DS1287, DS1287A, DS12887, DS12887A, DS12C887, DS12C887A, DS12B887, ODIN OEC12C887A, TH6887A, etc. See below for description of differences between these variations.
• The highly reliable Dallas RTC (Real Time Clock) is an integrated chip containing the system clock, CMOS memory, plus an embedded lithium battery to keep it all powered.
  • When new, a Dallas RTC chip is guaranteed to provide well over a decade of continuous, extremely reliable service.
• Dallas RTC chips have a very long specified design life of 10 years.
  • This limit is based on the shelf life of the small lithium coin cell embedded within the module.
  • High-quality lithium coin cells are said to have a shelf life of 10 years because at that point their slow self-drain has dropped their capacity to about 90% of the original capacity.
  • A fresh lithium battery starts out at about 3.3V and a typical loss of 10% capacity over 10 years leaves it with just below 3V, the point at which many devices stop working.
  • The Dallas RTC internal circuitry requires only 2.5V and draws only 500nA (0.0005 mA), which explains why they easily last 10 years, 15 years, or even longer.
• Being embedded in the chip, the internal lithium battery cannot be replaced, but fortunately, most Dallas chips are socketed so replacing the entire chip is easy and takes only a few minutes.
• Cheap Dallas batteries — the Dallas chips you see sold cheap (sometimes not so cheap) on the Internet are old pulls, very old stock, or counterfeit. New, geniune Dallas batteries are not cheap.
  • Be sure to look at the manufacture date on the chip — I have included a photo showing how to decode the Dallas RTC manufacture date. Old chips could still work, but not for long.
  • Cheap Dallas batteries can also be counterfeit. I've recently evaluated some cheap Dallas batteries which were fake. They looked brand new — I don't know whether they were repackaged old chips, or what they were, but they are mislabeled which proves they were not genuine.

Each purchase is for ONE new Dallas DS12C877A+ RTC chip as described.

• Be certain to orient the chip correctly when installing — the notch end has a dot or depression on top of the chip indicating pin 1 which should be oriented to the same end as in the notch on the socket.
  • Of course, the motherboard must be fully powered down when replacing the chip. Note that ATX type motherboards are not fully powered down by the computer switch. In the case of ATX, the power supply must be unplugged because ATX is always powered.
  • The chip will fit into the socket either way, but inserting the chip backwards or with the pins misaligned and power is applied, even momentarily, will instantly cause permanent damage to the chip. So double-check and be certain that you have it installed correctly before re-powering the motherboard.
  • The pins are thin and fragile so be careful that all the pins are aligned when inserting the chip. Sometimes the pins will get slightly bent from handling and will not enter their socket holes correctly. Before inserting, verify that all pins are straight and aligned. After verifying that the pins are aligned and entering their socket holes correctly, press the chip into the socket very slowly and carefully — if you feel resistance, forcing could result in bent pins so stop and double-check the pin alignment.
• The chance that a device like this comes defective from the manufacturer is — almost never.
  • Note that some motherboards will boot to the BIOS screen without valid clock and CMOS data, so installing this new Dallas RTC will not necessarily revive a dead motherboard (there are some exceptions).
  • A CMOS or clock error reported by the BIOS, especially after the computer has been powered down, generally indicates that CMOS battery is dead and cannot preserve the clock or CMOS settings — replacing an old expired Dallas RTC/battery with this new one will probably cure that specific problem.
• NO RETURNS IF ITEM SHOWS ANY SIGN OF INSTALLATION.

Shipped via fast USPS First Class Mail with full tracking. Shipped from a USPS regional SCF (Sectional Center Facility) so delivery anywhere within the U.S. is only a few days away (excluding the occasional USPS misdirect).

FAQ:

Q: Why are these more expensive than others that I see offered for sale?
A: Look at the date codes! Dallas batteries for sale cheap were probably made in the 1990's or early 2000's and are pulls from old motherboards. The ones listed as "NEW" may have never before been used, but the internal lithium battery is still as old as the date code says and will expire during the same time frame. Would you call something manufactured 25 years ago "NEW," especially if it has a non-replaceable battery? Look at the date code!
Even if the date code seems reasonable, counterfeit chips are being sold, which are probably repackaged old chips.
Back in the 90's these Dallas RTC chips were mass produced not only by Dallas, but clone equivalents were made by other manufacturers such as ODIN and VIA, so prices in that era were very low. Production now is for a few limited applications with long production lead times, so the current prices are higher.

Q: What does the "A" in the product code mean?
A: The "A" indicates that pin #21 is present (/RCLR), which triggers the chip's memory clear. If your motherboard has a "CMOS clear" jumper (as most do), shorting that jumper (while the motherboard is unpowered, of course) will short pin 21 of the Dallas battery to ground which clears the stored CMOS data (RAM associated with the RTC is not affected). If your motherboard has a CMOS clear jumper, then you want this A version. An alternate scenario is for the CMOS data to be cleared only through software, in which case there is probably no electrical connection to pin 21. The DS12887 (without the A), is the same chip except pin 21 is absent. In worst case, if pin 21 causes a problem, just bend the pin so it doesn't connect. For these reasons I have chosen the "A" version because it is universal, is required in most cases, and works in all situations.

Q: What does the "+" mean?
The plus designation indicates that the device is lead-free, therefore preventing this toxin from leaching into the environment. RoHS (Restriction of Hazardous Substances) restricted lead content in electronic products with compliance required after 2006. Therefore, if a Dallas RTC does not have the "+" indication, that's a solid guarantee that it was manufactured before 2006.

Q: What is the DS12C887?
The "C" version has a century byte so the RTC can keep track of the century during the changeover from 1999 to 2000, otherwise either the C version or non-C version will work the same. Factory: "The century register at location 32h is a BCD register designed to automatically load the BCD value 20 as the year register changes from 99 to 00. The MSB of this register is not affected when the load of 20 occurs, and remains at the value written by the user." It's possible that the Century byte could help with old BIOS with Y2K problems.

Q: What is the DS12B887, and can this replace it?
A: I have not run across the "B" version and cannot identify any differences, but this is what the manufacturer says: "The DS12B887 Real Time Clock was obsoleted over 16 years ago. The best alternative for the DS12B887 is the DS12887A, mostly because of the /RCLR function."

Q: What is the DS1287, and can this replace it?
A: The DS12887 is a new design replacing the older DS1287 which was discontinued years ago. Manufacturer: "The DS12887+ is a direct pin-to-pin replacement for the DS1287." (And the DS12877A+ is a direct pin-to-pin replacement for the DS12887+, except for the addition of pin 21 which, when activated, clears the CMOS memory. See FAQ about the "A" version above.)