The Philips PCA761AW (or EC251?) Interwave card has been discussed a fair bit on this forum over the years - from here: EC251 InterWave Audio Card (which details how to add memory to it)
To the Newly Made GUS thread where Shock took the card apart, derived a schematic from it and designed the ARGUS PCB 😀

I got hold of one of these cards a month or two ago here: Re: Bought these (retro) hardware today
It's frustrated me so far, I thought I'd fit a 42-pin 2MB SOJ in the footprint of the 40-pin SOJ, but that didn't work for me yet. Instead, I went the route other people have and put a 40-pin SOJ socket on the footprint for the RAM. That works with a 256k x 16 (512KB) that came from a dead laptop - following lots of posts in the new GuS thread, I found out how to reflash it to think it's a Gravis Ultrasound PnP and the drivers work with it, cool!

But reading through the 2012-2014 thread, it seems that 512KB isn't the best. That's all the card's PCB is designed for though, how to get more?

There is tons of information in the Newly Made GuS thread - Shock depopulated the card and shared pictures so I can see what traces go where. Looking at the ARGUS, I can see that it can address two SOJ memory chips - eventually worked out which pins those go to on the datasheet. On this card, the extra pins for bank selection of more memory banks go nowhere:

Both RAM chips have the same address lines and data lines, the only change is the BKSEL0/1 and BKSEL2/3 lines (LCAS and UCAS on the chips themselves, each 8 bits I guess). So I stacked a SoJ ontop of another by straightening out its pins, bent the UCAS/LCAS legs out so they could go elsewhere:

Those wires go off to the two bank select lines, this was not fun to solder - the wire I used was somewhat bigger than needed:

Looks pretty normal now it's all installed:

And here it is in Windows with both banks populated 😀 Now to figure out how to use this card properly - so far all I've managed to do is play a couple of demos from the Ultrasound install CD.