Tantalum caps from a good quality late 90's device are not going to spontaneously combust any time soon - I'm not sure why you are so anxious; caps like these are in many vintage devices you probably own and not needing replacement. In the rare event they do blow, the damage is often just around the tantalum cap footprint itself and easily replaced.

Is this really 8Mb ? looks like 4Mb
isnt 8Mb ZX SDRAM only ?

No, the ZX exists in SGRAM form as well and it's the one to look for as the SDRAM version is only 64bit and thus very slow.

Yea, says 8MB in the bios message at post as well as DirectX config in Windows 95. Datasheet for the memory chips show they are 2MB SGRAM.

https://pdf1.alldatasheet.com/datasheet-pdf/v … 636327Q-10.html

I went ahead and ordered the aluminum poly caps, as well as a new e-cap to replace that tiny 4mm SMD one which is likely dried out. I know I am being paranoid, but these things are 22 years old at this point and I don't want to risk the destruction if one of the tants shorts out. I'll post an update once they are replaced.

Riva 128ZX came in 3 flavors:
4 Mb SGRAM 64-bit bus (only 2 chips on board)
8 Mb SDRAM 64-bit bus
8 Mb SGRAM 128-bit bus

Replaced the caps, perfect fit-wise. And even though the polymer are much lower ESR, it didn't seem to effect anything. Output is still great.