- It is not possible to build a ready to use NIC because the connector for the G2 bus is a custom part made exclusively for SEGA.
It is difficult to make your own female connector from scratch. The only thing I can think of is with 2 PCB - one above and one below the card edge lined with conductive elastomers. The elastomers allows you to make reliable connections with the pads as PCB tends to warp and thus do not have perfect flatness.
There are also card edge connectors that have half the pitch (pin spacing). These connectors have pins at 2 depths. Take a look at an old AGP card and you'll see what I mean. Also take a look carefully at the marks made by the connectors on the gold fingers on your card.
1mm pitch card edge connectors with staggered pins that I know of:
- AGP - too short
- Pentium II connector (difficult to order, but easy to find from junk motherboard)
- NLX riser connector
Here is what they looks like:
The bad news is that the outside of the connector is too big to fit the Dreamcast. There is a plastic hood surrounding the connector in the Dreamcast. This is part of the one piece Dreamcast connector. You'll need to align and cut down your card edge connector, file down the thickness and also file off 2 corners to match the keying.
Also the surface mount FCI Conan connector in figure 2 looks interesting. Might work if you make a PCB and use modified (as in cutting off the edges) 2 of these and mount side by side.
Looks like the opening is around 0.050" which is insufficient. Need to make an extra cut.
The RTL8319 unfortunately expects 32-bit wide data on the PCI bus and uses bus mastering for receive data. You'll need to make a dual port memory buffer which would requires programmable logic and/or dual port memory. This is not a weekend job and certainly too complex for the majority of people.
If you only want to run BSD and write your own code (i.e. no software compatibility to BBA), then there are schematics on the net for hooking up ISA 10 BaseT card.