If you have the Spacemaster: Privateers collection:
4512PEquipmentManual.pdf page 60, could use listed numbers as per Mk#
In SM2 collection:
9000cP-TechBook.pdf, the only reference is exactly like you said in the first post: Microcomputer (Mk. 1 through 4)
Otherwise, to be honest, I don't think there are any other references for computers. I went through all my Spacemaster materials and only found references for ship-based computers. And that was with the older SM2 system. The SM:P system has no references to any kind of computer except how much it costs for only two programs (Ship Maneuvering Prediction and Ship Maneuvering Evasion, called Predict and Evade).
Sorry, not much more help can I give, except below.
However, if you think about how much computer technology and software power has increased in just 40 years (I built my first computer inside a wooden cabinet with only 1KB RAM and had to store programs on casette tapes in 1976), simply let your imagination run free. Hell, in 1984 I was called a "crazy idiot" or a "f_____g retard" for saying computers will be the size of credit cards inside 30 years. By 2014, what was the size of some of the smaller smart phones? I'd love to meet some of those guys and gals today and ask, "You remember what I said about computers 32 years ago?"
If you want computer power, I can imagine my netbook computer that is only 17.5cm × 12.5cm × 1.5cm having more computing power than all of Google's server farms. And that would not be including the possible "cloud computing" power it could also tap through the SCONE (Superluminal COmputer NEtwork). And I could simply say this is only a Mk. 5 computer.
And such computers would probably not cost much more than today's computers, percentage of salary wise anyway.
Thus, use your imagination. I think that is all I did those many decades ago when sci-fi role playing. And still do today.
rmfr