Great find - do post some pics of the other 386 and 486 motherboards (and provide some details about them).

1. On some motherboards, it can take some time for the settings to be lost. However, 36 hours seems to be a bit too excessive.
   In some cases, you can discharge (clear) the CMOS memory via a jumper.
2. Just be careful on what type of batteries you connect to the external battery header.
   I also have a 386SX motherboard that actually has two external battery connectors.
   One is meant for rechargeable batteries and the other one for normal alkaline (non rechargeable) batteries. At first I connected my normal alkaline batteries to the chargeable connector and (fortunately enough) noticed that they were getting very hot.
   Normally, the outer pins are used for connecting to an external battery. On some motherboards, there is usually an indicator (in the form of a "+" sign) right next to one of the outer pins to indicate which one is the positive connection.

Take note, on some of my older boards, I actually had to use a 4x AA battery holder (which gives me 6V in total) in order to ensure that my motherboard settings are stored.
Here is also a good resource that you can refer to: http://pc-restorer.com/replacing-cmos-batteries-in-old-pcs/

jesolo wrote:

Great find - do post some pics of the other 386 and 486 motherboards (and provide some details about them). […]
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Great find - do post some pics of the other 386 and 486 motherboards (and provide some details about them).

1. On some motherboards, it can take some time for the settings to be lost. However, 36 hours seems to be a bit too excessive.
   In some cases, you can discharge (clear) the CMOS memory via a jumper.
2. Just be careful on what type of batteries you connect to the external battery header.
   I also have a 386SX motherboard that actually has two external battery connectors.
   One is meant for rechargeable batteries and the other one for normal alkaline (non rechargeable) batteries. At first I connected my normal alkaline batteries to the chargeable connector and (fortunately enough) noticed that they were getting very hot.
   Normally, the outer pins are used for connecting to an external battery. On some motherboards, there is usually an indicator (in the form of a "+" sign) right next to one of the outer pins to indicate which one is the positive connection.

Take note, on some of my older boards, I actually had to use a 4x AA battery holder (which gives me 6V in total) in order to ensure that my motherboard settings are stored.
Here is also a good resource that you can refer to: http://pc-restorer.com/replacing-cmos-batteries-in-old-pcs/

Thanks for the info!

I have posted a little more about these in some other threads.

Re: Need help with my first 486 boards.

Re: What retro activity did you get up to today?

... though I guess the 386 hasn't been covered much. I'll have to take some pictures of it and post some of the benchmark results soon.

I just wish I had a proper case for it. Its a super tiny board, so putting it into a full size AT case seems a bit funny when there are already newer full size boards in those cases. I have a really spiffy tower with a full 3 digit turbo LED, which is probably better suited to a 486DX4 or something. I guess I could use a tiny ATX case and just do some modifications, but I'm pretty sure this has too many slots for a Micro-ATX. I already have a couple AT-style ATX IO sheilds with just a 5 pin DIN keyboard hole.... hmmmmm... I'll have to see what I can do.

Ozzuneoj wrote:

... though I guess the 386 hasn't been covered much. I'll have to take some pictures of it and post some of the benchmark results soon.

Well Post your 386 Speedsys results here

elianda wrote:

Ozzuneoj wrote:

... though I guess the 386 hasn't been covered much. I'll have to take some pictures of it and post some of the benchmark results soon.

Well Post your 386 Speedsys results here

Will definitely post there when I get some results. 😀

Resurrecting an old thread one year later...

I finally got around to installing a 3xAAA battery holder in the DTK 386 board mentioned in the first post, however, it is no longer posting! I used a POST card and it is showing that it stops at code 16. I don't know exactly what BIOS is on this thing (it just says DTK DATATECH 386SX 3150 4.26 on the chip), but in the manual for my POST code reader it seems there are several references to the 8254 timer (AMI) or the 8259 timer (AWARD).

I'm at a loss here. Yesterday I disconnected a diode to disable the battery charging circuit. I tested the system afterward with a CR2032 3v cell and the system worked fine but it wouldn't hold the CMOS settings. I read that several people found that 286 and 386 systems needed more voltage than that to keep the CMOS settings, so today I put together a 3xAAA holder for it. The documentation is a bit vague as to which pins on the external battery header should be connected to, so I just found the ones that had continuity (in both directions) to the internal battery's terminals. I powered the system on (with no CR2032 or AAA batteries or vga card installed) and doubled checked that there was no voltage coming across the battery holder (just in case!) and there wasn't. So I installed the batteries, tested the system and it will not POST. Even with no batteries at all I get the code 16 every time. Removing all of the RAM gives me a code 5. Removing the BIOS chip all together gives a blank code readout. So, it isn't completely dead, it is just getting hung up on code 16 or 17. Also, there are no beeps from the speaker header, I've tried several speakers too.

Did I do something wrong here? There are dozens of sources online saying that 4.5v from 3x alkaline batteries is safe on old boards. Is it most likely an unrelated issue? The board did have battery corrosion damage so it's possible that some other trace has given out... but I just don't know.

Fixed the issue. I had a few more traces that were not reliable, so i ran some wires and now it's working again!

Now, the batteries seem to be holding the time and date but for some reason the amount of memory keeps getting reset after being unpowered a while. Any reason why some settings would be kept and others wouldn't?

As far as retaining settings goes without the battery, the SRAM used to hold the settings is incredibly low power and can last off the residual charges in capacitors for a while. Only sure way to wipe the settings is the short the power line of the SRAM circuit to ground. With no sort of power at all (i.e severed trace etc.) the settings will not last more than some tens of minutes, and will progressively get more corrupt as minutes pass. It is amazing how little power is needed by that hundredish bytes of storage. RTC will not run though, that needs some more current to operate.

Sorry, rather than resurrect this old thread I probably should have just linked to this thread from my more recent one... I'll post updates there.

386SX 33Mhz motherboard... need some help!