Which card is it?
Open the system and take it out.
Look for its part number, on a bar-code sticker.
We'd need the first seven digits of the information.
501xxxx or perhaps 370xxxx or maybe 375xxxx.
Some Sun cards are PCI cards, but some are not PCI cards.
Let's get that part number, first.
You could always just try it.
If it is truly a PCI framebuffer, then it would fit into a PCI slot properly
and your OS might just recognize it.
You wouldn't 'break' anything.It would work, or it would just not work.
For example the PGX32 cards are just rebranded TechSource cards
and WinXP recognizes them natively as a 2D card.
That XVR-100 ( P# 375-3181 ) card will probably not work in a PC.
Granted, it's an off-the-shelf ATI card, but it's the version
that requires an OBP in the computer, instead of a BIOS.
It's an ATI Radeon MAC Edition 64MB 2D framebuffer.
Apple and Sun SPARC systems don't have a BIOS,
but a different sort of low hardware layer for their systemboards.
The eeprom on the graphics card expects to interface
with that other sort of systemboard design.
You are welcome to play with it; you won't "break" anything.
( ... and the S-video port is non-functional, by the way )
If I were to try it, I'd scrounge around the Internet for OLD drivers
rather than use new ATI Catalyst bloatware.
Go to ATI's web site and search their knowledgebase,
using "radeon 7000" as your keywords.
Read the white papers and FAQ's that come from such a search.
For example, here's the ATI product manual, from their web site:
https://support.ati.com/ics/support/KBAnswer.asp?questionID=1180
There are Sun-specific manuals for it at the Docs.Sun.Com web site.
If you have a Spectrum login account to Sunsolve, there are product details
in that version of the Sun System Handbook, but not the public (free) SSH.
I wouldn't expect much success with the XVR-100 card in a PeeCee.
Now ... in an Apple G4 ?That's a different story.