Well, is there a jumper for video memory? I see some corrosion beside the ISA slot, check it out.

https://theretroweb.com/motherboards/s/packar … rev.c#downloads

From manual

If board is factory installed with 1MB of VRAM, a second 256K x 16 DIP will soldered on the board at U22. If board is factory co […]
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If board is factory installed with 1MB of VRAM, a second 256K x 16 DIP will soldered on the board at U22.
If board is factory configured with 512KB of VRAM, U22 will only be a trace, and a 40-pin ZIP socket will be
installed at location U20. If the ZIP socket is present, there will also be traces for 2 additional zip sockets
at U14 and U16. Sockets installed on ZIP socket traces will not function.

The picture of the motherboard and onboard video chip are archived pictures from when I first disassembled the computer a couple years ago. All corrosion was removed in the cleanup and assembly that followed. The picture of the populated ZIP socket is current to this issue.

When I read the manual document, similar to the one dominusporg linked, there is mention of a jumper to enable/disable onboard video but nothing for video memory.

How about the BIOS? Is there an option regarding video memory? Another option is to solder a second chip similar to NEC on the motherboard.

I think that ZIP memory you bought is unfortunately incompatible with this motherboard 🙁
Both of your memory chips (424260 and 424170) are NEC branded, and both are 256kBx16, but in datasheets you can see that they are different types.

Moreover support page http://www.uktsupport.co.uk/pb/mb/410.htm says that "Video memory is upgraded by installing a 256KBx16 70ns or 80ns DRAM ZIP at location U20. The ZIP needs to be ASYMMETRICAL (Write Enabled). This DRAM ZIP is not the same chip used for PB430/440/440T upgrades."

zyga64 wrote on 2023-08-26, 21:40:

I think that ZIP memory you bought is unfortunately incompatible with this motherboard 🙁
Both of your memory chips (424260 and 424170) are NEC branded, and both are 256kBx16, but in datasheets you can see that they are different types.

Thank you. This is good information. I see they are different starting at pin 22. I worried the ZIP memory I bought might not be the right one. When I researched it pre-purchase I didn't find a lot of information and just took a chance with what was available on eBay.

So if I can find the correct ZIP memory it could still work with my motherboard.

While waiting for more RAM you could try this small program on your Headland graphics to see if it has the unused random function that only a hand full of graphics cards implement...
Can your VGA card provide a hardware source for random numbers?
You can post your results there if you are interested. That would be great.

stuartmcivor wrote on 2023-08-26, 22:44:

zyga64 wrote on 2023-08-26, 21:40:

I think that ZIP memory you bought is unfortunately incompatible with this motherboard 🙁
Both of your memory chips (424260 and 424170) are NEC branded, and both are 256kBx16, but in datasheets you can see that they are different types.

Thank you. This is good information. I see they are different starting at pin 22. I worried the ZIP memory I bought might not be the right one. When I researched it pre-purchase I didn't find a lot of information and just took a chance with what was available on eBay.

So if I can find the correct ZIP memory it could still work with my motherboard.

Did you ever find a working module for your upgrade? I've been tinkering with a PB410 as well and I'd be curious to know what you found.

No. I would still like to.

The motivation for the memory upgrade was so that I could use 256 or greater color at higher resolutions; 1024x768 if memory serves. MS Office's Word and Excel would crash at lower color settings. As the computer is used mostly for DOS games I eventually gave up and spent my time playing Wolfenstein and Spear of Destiny.

Maybe one day someone who knows will post the right information.