Care to post a photo of your board so we can have a good look ourselves? Also the retro web would be interested in a good photo.

as for the JBAT, I think the lonely pin is positive, the other side pin is negative, the expected voltage is between 3 to 6 volt, ie 2 to 4 1,5V AA batteries.

Here is the best picture I can get at the moment. Sorry for the quality, it's a bit tight in that part of the case. I will try to get a picture of the full motherboard at some point. It seems like my motherboard more closely matches this entry: https://theretroweb.com/motherboards/s/dell-s … 316sx-cr,-325sx

https://i.ebayimg.com/images/g/zjMAAOSwMvpm-9ol/s-l1600.jpg

Looks like a "regular" external battery connector. First pin is V+, and empty pin (key) and 2 GND pins. You can confirm that by measure continuity between the last two pins and some ground point on the MB, it should be close if not exact 0 Ohms. The first pin goes through a diode and/or other circuitry to a 6818 (https://theretroweb.com/chips/4559) or something like it on the MB. Most of those accept wide range supply voltage between 3 and 6 volts. But you need to take to account the v-drop of the circuitry between the connector and it.

Looks like those batteries are planed to be 4.5V Re: Buying external 3.6v battery pack with leads. What I personally prefer is a double CR2032 box (or 2 sockets connected together) with those connected in a row. An extra zener before the connector, so when new CRs are put the voltage should be no more than 6V.

I checked with a multimeter, and there is continuity between the two adjacent pins as well as between each of those pins and the outer case of the power supply (which I assume is grounded). So that makes it seem like the two last pins are ground.

If I purchased this AA battery holder from DigiKey: https://www.digikey.com/en/products/detail/mp … H3AA-211/221551, should it work? I'm not sure what you meant by "an extra zener before the connector".

Yep, the 3xAA should be fine and should last long time. Just make sure that there is no current on the connector by measuring DC Voltage between pin 1 and pins 3 or 4 while the machine is powered on. If there is current there, then you should put a diode, preferably schottky on the positive cable between the battery pack and the connector, so no current passes to the battery pack.

The CR2032 when new, provides more than the stated on its top 3V. Normally around 3,2-3,25V. So two of those in a row will add up to 6.5V, which if not lowered below 6V by the circuitry on the MB before the 6818, sometimes there is only a schottky there, it can damage the chip. So that's the reason to limit the current of the 2 CRs in a row before connecting them to the header for external battery.

P.S.
Keep in mind that the alkaline batteries also tend to leak after time. Place the battery holder as far away from the MB as possible. Not that the CRs never leak, but it's quite uncommon to see those to spill.

You sure you don't have a socket for the DS1278 near the RAM slots? I bought a 316SX last year and had to replace the DS1278 with a Necroware replacement.

oso2k wrote on 2025-01-03, 02:18:

You sure you don't have a socket for the DS1278 near the RAM slots? I bought a 316SX last year and had to replace the DS1278 with a Necroware replacement.

I don't see a socket for the DS1278 near the RAM slots. The only chip I see near the RAM slots is a single BIOS ROM.

SpoXi wrote on 2025-01-03, 00:05:

Yep, the 3xAA should be fine and should last long time. Just make sure that there is no current on the connector by measuring DC […]
Show full quote

Yep, the 3xAA should be fine and should last long time. Just make sure that there is no current on the connector by measuring DC Voltage between pin 1 and pins 3 or 4 while the machine is powered on. If there is current there, then you should put a diode, preferably schottky on the positive cable between the battery pack and the connector, so no current passes to the battery pack.

The CR2032 when new, provides more than the stated on its top 3V. Normally around 3,2-3,25V. So two of those in a row will add up to 6.5V, which if not lowered below 6V by the circuitry on the MB before the 6818, sometimes there is only a schottky there, it can damage the chip. So that's the reason to limit the current of the 2 CRs in a row before connecting them to the header for external battery.

P.S.
Keep in mind that the alkaline batteries also tend to leak after time. Place the battery holder as far away from the MB as possible. Not that the CRs never leak, but it's quite uncommon to see those to spill.

Thanks for the information. I checked the voltage between the pins with a multimeter, and I was getting a reading of 0.3V. Is this insignificant?

It sure would be great if you could get a clean photo of the mainboard in all its glory. It would definitely benefit theretroweb as well.

weedeewee wrote on 2025-01-04, 20:46:

It sure would be great if you could get a clean photo of the mainboard in all its glory. It would definitely benefit theretroweb as well.

Yes, I am planning to get a full picture of the motherboard when I have time to pull it out of the case.

uniracers wrote on 2025-01-04, 20:35:

Thanks for the information. I checked the voltage between the pins with a multimeter, and I was getting a reading of 0.3V. Is this insignificant?

Looks like schottky reverse leakage, the reverse current will be minuscule.

Look for 24 pin IC. If Dallas (or equivalent) with integrated battery and 32kHz crystal, it will be significantly (more than 2 times) taller that the rest of the ICs. In such case you should replace it or mod it's battery. Or it can be just a 6818, "external" 32kHz and a cap located around, which will take power from the "JBAT" connector. Third case covers the second one, but the functionality of the 6818 is integrated in some IC of the chipset.

It only took me almost five months, but I was finally able to get the motherboard out of the chassis and get a picture of it.

A photo for trw

Deksor wrote:

Seems like the RTC is integrated into the 82c106
https://bitsavers.trailing-edge.com/pdf/dec/d … eets/82C106.pdf
VBAT pin 69 Normally 3 V to 5 V.

Did you order that battery holder and get it working ?

The initial (wrong) link is for one with a Western Digital/Faraday chipset, you have a different board, the 316SXcr:
https://theretroweb.com/motherboards/s/dell-s … 316sx-cr,-325sx

there is archived documentation on the Dell System 3xxSXcr:
https://web.archive.org/web/19961222131734/ht … 5sx/default.htm