What type of Dallas RTC chip did you get? The big box one (like the DS12887) or the unusal "standard chip"-sized one (like the DS12885)? The DS12887 chips do not have the pins that connect to the main board battery, so there is no point of adding a Nickel rechargeable pack or a Lithium coin cell to the board when you use a DS12887. In the DS12887, the power supply is self-contained inside the chip, and if that chip started ticking its clock (it comes factory-shipped with the clock disabled!), it depletes its battery in around 10 to 15 years. So if the "new" DALLAS RTC chips you got are actually pulls from 1990s computers with their clocking ticking, it's expected that the battery is depleted by now.

There are threads here on VOGONs about adding your own power supply to depleted Dallas chips. My preferred method is to use a dremel to disconnect the internal depleted battery, and add the missing pin to connect the power connection of the RTC chip (in the DS12887 box) to the power trace provided on the mainboard, and then use the battery holder on the board to provide power. But the "holder glued on the DS12887" method works fine as well.

The RTC is the DS12B887. I was assured that they were new and not pulled from old machines. They look new too.

i2lgames wrote on 2020-12-20, 11:42:

The RTC is the DS12B887. I was assured that they were new and not pulled from old machines. They look new too.

Do you have any other computer to test these chips in? The DS12B887 has a self-contained system that contains the battery and monitoring the battery level. If that system reports the battery is low, then the battery is low. There is nothing outside of the chip that can influence this report. Well, maybe there is. The original DS12887 (without the A) didn't have pin 21 for clearing the CMOS RAM. If your board inadvertendly grounds this pin, or the clear CMOS jumper is permanently set to "clear", it might cause the symptom you have. Another possible, but unlikely cause of the symptom is that the original DS12887 chips ignored bit 6 when selecting the RAM address/clock register to access, whereas the DS12B887 has 64 extra bytes of RAM selected by this bit. If the BIOS relies on the bit being ignored, it's incompatible with this Dallas chip. I don't know of any BIOS relying on this bit to be ignored, though.

First of all I would like to thank you for you suggestions. I am not sure if the clear cmos jumper is bridged. I will have to check it. Unfortunately, or fortunately now that i think of it, this is my only board with a DALLAS RTC. My other 486 motherboard uses an external battery pack.

Nope, my version of the HOT-433 doesn't have a clear cmos jumper. I should start hacking then...

Where did you get these dallas chips ?

Fake chips from china is a problem and dallas clocks make no exception. Can you show us any photos of them ?

Here it is, as i bought it
https://www.ebay.ie/itm/3pcs-DS12B887-Integra … 353.m2749.l2649

It may be just me, but if you look closely, on the middle of the left side of the chip, you can see the shape of a notch like there are on most ICs to indicate where pin 1 is. But it looks like it's covered by paint ...

Again, it's hard to tell with a photo. Can you rub your chip with a q-tip with alcohol ? If black stuff wears off it's definitely fake (but if it doesn't that doesn't mean that it's not fake).

Well... black stuff wears off... I guess it is fake then...

You should ask for a refund. Fakers usually repay you right away.

Then you can try to mod the old battery that way https://www.youtube.com/watch?v=xBvw1TLHyqM (or use the faked modules instead, I'm sure they're true dallas batteries under the hood, except that they must be old chips pulled from boards).

Ok, gutted it and soldered the leads to my coin cell. All ok now. Do anyone know where to source reliable DALLAS RTC's in Europe?

Deksor wrote on 2020-12-20, 16:27:

(or use the faked modules instead, I'm sure they're true dallas batteries under the hood, except that they must be old chips pulled from boards).

Might also be some Dallas clone, like the ODIN chips that were also quite common in the 90s. But I agree that the repainted chips most likely are Dallas chips or clones that you can revive using an external battery.

mkarcher wrote on 2020-12-20, 17:14:

Deksor wrote on 2020-12-20, 16:27:

(or use the faked modules instead, I'm sure they're true dallas batteries under the hood, except that they must be old chips pulled from boards).

Might also be some Dallas clone, like the ODIN chips that were also quite common in the 90s. But I agree that the repainted chips most likely are Dallas chips or clones that you can revive using an external battery.

These were definitely older dallas chips.

A likely cause is also that the original chip was one of the Dallas modules that didn't have the "clear CMOS" pin.
Some motherboards will tie this position to ground or use it to route another signal if they used a full 24-pin DIP footprint.
The solution is to cut off the pins that are not required for your situation: easiest thing to do is match the missing pins on the original module.
Just snip them off or bend them up if you don't want to cut.
As far as I can remember, the cause is PIN 21 on the new module. The old one doesn't have PIN 21.

JimWest wrote on 2020-12-21, 16:16:

A likely cause is also that the original chip was one of the Dallas modules that didn't have the "clear CMOS" pin. Some motherb […]
Show full quote

A likely cause is also that the original chip was one of the Dallas modules that didn't have the "clear CMOS" pin.
Some motherboards will tie this position to ground or use it to route another signal if they used a full 24-pin DIP footprint.
The solution is to cut off the pins that are not required for your situation: easiest thing to do is match the missing pins on the original module.
Just snip them off or bend them up if you don't want to cut.
As far as I can remember, the cause is PIN 21 on the new module. The old one doesn't have PIN 21.

This is interesting. The pin 21 is present in all the chips i got! I will remove the modded one, bend the pin 21 and test again.

Thank you.