IBM 5160 with oddball MDA input/output card

[Jules Richardson via cctalk]

Hi all,

Someone on one of the Facebook vintage groups found an IBM 5160 with an MDA 
display for sale in Australia, except that it's a bit odd in that the 
machine had what appears to be an MDA card, the output of which is then 
connected via a short external cable to the input on another card, and then 
an output that card is what's actually hooked up to the monitor.

The only internal photo of the machine is very poor, unfortunately. I'm 
reasonably confident that the "first" card in the "mystery" chain is MDA, 
it's full-length and alongside the DE-shell video output has the usual 
DB-25 for parallel. The "mystery" card is also full-length, and there's 
another full-length card immediately adjacent to it with no external 
connectors - that one could easily be RAM, or the hard disk controller etc. 
 but I suppose it's possible that the mystery item is actually a two-card 
set.

Anyway, any guesses as to what it might be? The implication is that the 
mystery card adds functionality to the MDA card (reminiscent of 3DFX boards 
years later), but of course is operating within the confines of what the 
MDA display's capable of.

cheers

Jules