I can't give you an exact answer -- never owned one! -- but I can talk a little bit more about termination, to maybe help you figure it out on your own in a very roundabout way. This may be more than you want to bite off, but I'm just putting down the information for reference in any case.
Basic termination is all about preventing reflection of signals at the end of a
transmission line. Each individual address/data line on a computer bus qualifies as a transmission line. Simplistically speaking, the longer the line and the faster the speed of the bus, the more these reflections end up being an issue if proper termination isn't achieved and which cause interference / "ringing" issues along the length of the line (e.g. where various cards are inserted and tap off of it). Ideally the termination load is exactly equal to the transmission line impedance which is exactly equal to the source impedance (in Ohms). But, the amount of reflection will be in proportion to the match between the termination load and the source and trace impedance of the line, which means that you may be okay with "close but not quite" termination.
There are two common forms of termination, passive and active, which you can see in this image poached from
interfacebus.com's SCSI bus page:
Passive termination generally has resistance between the signal to one or both voltage rails. The actual impedance of a single ended SCSI bus is about 132 ohms, which explains the 220 and 330 ohm resistors above. The impedance of the termination here is the total impedance of the signal path to both power rails, and so the 220 ohm and 330 ohm resistors should effectively be considered in parallel: 1/(1/220 + 1/330) = 132.
Active termination generally has resistance between the signal to some sort of mid-point regulated voltage. You can see that on the far right diagram, where the signal goes through a 100 ohm resistance to a 2.85V regulator, providing 100 ohms of termination resistance, close-ish to the 132 ohms of the passive terminator.
If you want to figure out what to do, you should figure out whether the termination is active or passive. Active termination will generally have a resistor per bus line going to a mid-point voltage source somewhere between the two rails. Passive termination will have a resistor per line to a voltage rail (e.g. +5V or 0V), or two resistors to two rails (e.g. +5V and 0V).
The next thing you'd want to figure out is line impedance, so you can decide what to terminate at. Sometimes the impedance is set with a resistor at the source, e.g. Rs in the diagram below (from
Proper Termination of High-Speed Digital Signals):
If this is the case you may be able to find that resistor to determine impedance, though I think this is less common in the computer bus context. If you don't see anything like that then more likely the impedance is determined by the driver and the traces on the board.
I think some good news is though that most of what I've seen is in the 100-300 ohm range. For example, VME bus is a 100 ohm impedance, terminated with 194 ohms (
VME Bus Description, interfacebus.com).
You could attempt to determine what type of bus it is and look up what impedance it has, or alternatively just start trying to terminate in the 100-300 ohm range (with whatever configuration of resistors achieves that). That's up to you and your knowledge of electronics and your assumption of risk. I disclaim any responsibility for outcomes, good or bad
(though a 5V signal into 100 ohms is only 50mA, and ~16.7mA for 300 ohms, so hopefully nothing is going to get upset).
