If it's on-board, it's most likely either 512 KB or 1 MB. The 5428 was the lower-end of the CL VGA chips and was normally not used with 2 MB.

derSammler wrote on 2020-02-26, 20:07:

...the CL VGA chips and was normally not used with 2 MB.

On closer inspection of the info on the 5428 it says it supports "up to" 2mb 😳

I'd still like to know if there's a way of finding out the amount of video ram though.

Could there be something in windows 3.1 that'll reveal all?

Run some diag software like Dr. Hardware or simply look at the DRAM chips on the mainboard. They tell their size. If unsure, post a picture.

The 5428 can be configured with either 1MB or 2MB DRAM. If you have any free sockets on your card you have 1 MB. If they are all populated you have 2MB.

The only difference the 2M upgrade will make is enabling of the following three extra resolution modes:

1024 × 768 × 32K (interlaced)
1024 × 768 × 64K (interlaced)
1280 × 1024 × 256 (interlaced)

They are all interlaced resolutions due to the shitty DAC in these chips so this is not actually useful for anything. There are no other benefits. You won't get even 800x600x16M as some other 2M cards can do.

mpe wrote on 2020-02-26, 22:29:

The 5428 can be configured with either 1MB or 2MB DRAM. If you have any free sockets on your card you have 1 MB. If they are al […]
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The 5428 can be configured with either 1MB or 2MB DRAM. If you have any free sockets on your card you have 1 MB. If they are all populated you have 2MB.

The only difference the 2M upgrade will make is enabling of the following three extra resolution modes:

1024 × 768 × 32K (interlaced)
1024 × 768 × 64K (interlaced)
1280 × 1024 × 256 (interlaced)

They are all interlaced resolutions due to the shitty DAC in these chips so this is not actually useful for anything. There are no other benefits. You won't get even 800x600x16M as some other 2M cards can do.

That pretty much answered my next question 🤣

Thank you for your sharing your time and knowledge!