Unfortunately, it is not possible with the Voodoo4/5-series to combine two separate boards in the same system for commensurate performance gains, unlike 3dfx's initial SLI foray with Voodoo2 and now nVIDIA's significantly improved version (GeForce 6 series and later) as well as ATi's CrossFire (X800/X1K).
With it's Voodoo4/5-series products (VSA-100), 3dfx leveraged the SLI branding made popular with multi-card Voodoo2 products in two PCI slots connected via dongle, into a single card, multi-gpu (1x-4x per board) product. The 4-gpu version (Voodoo 5 6000) was never mass-produced, although a handful of various (some working) prototype revisions are in the hands a few tech enthusiasts and occasionally pop up on E-Bay for a king's ransom.
3dfx integrated the SLI capability to the board level with Voodoo4/5, due to the prevalence of the AGP specification for high-end graphics cards at the time, which limited any multi-card setup due to the differing frequencies and bandwidth between the AGP and PCI buses -- getting two cards to communicate over two different buses with different latencies, etc was not viable at the time.
However, MetaByte (a popular Voodoo2 manufacturer) were working on a system called
StepSister, that promised to solve the problem I described above, i.e. allow an AGP and PCI to be utilised in a SLI-like fashion. Unfortunately, Wicked3D pulled out of the extremely competitive graphics market in May 1999, a few months after previewing their StepSister technology. A few years later, Alienware spent considerable resources developing a similar system, only to be displaced by nVIDIA's improved SLI implementation with the arrival of high-end PCI Express penetration in late 2004.
As far as playing Prophecy today, any graphics card released in the past 6 or 7 years should have no problem playing the game and with a decent GLide wrapper, such as
Zeckensack's, the game can be played in it's native API. The increase in GPU processing power, complexity and parallelisation over the past decade is quite astounding -- 3dfx's SST-1 (Voodoo), fabricated almost 10 years ago comprised 1-million transistors compared with ATi's R580 (X1900XT/XTX) which tops current complexity at 384-million transistors!
HCL's upcoming patch for even higher resolutions and widescreen support will probably require a more recent graphics card if you push the resolution up, but even with a typical card today, Prophecy should be playable at the extremes with high levels of AA and AF, as well as extras such as Adaptive AA(ATi R3xx/X800/X1K-series)/Transparency AA(GeForce 7-series), which improves AA on alpha textures, although I wouldn't think there would be many or even any in an engine of Vision's vintage.
Cheers,
BrynS
