IIRC, actually Squire did not have the stock Rick-O-Sound on his bass. He had the bass rewired to run each pickup to a separate output. Same idea though.
Again IIRC, his earliest rig was 2 Fender Dual Showman amps with Fender cabs and at some point he switched to running Sunn cabs, 612 and 610 I think, one of the Sunns being a guitar cab. You can hear the speakers on the guitar cab on the verge of ripping apart on "the Yes Album".
Later, I believe one of his Fender amps was replaced with a Sunn head.
He also had a piece of gear called a "Frequalizer", some sort of parametric EQ.
He's gone through several incarnations of his rig, but his current rig, as JimmyM said earlier, is a Marshall Superbass with 2 Ampeg SVT IIs, and 2 810e cabs. Bass pedals go through an SWR SM500 (I think) and SWR 215 cab.
Strangely enough, I used to get a "Squire-esque" tone out of my old Ampeg V4B. I used a very strange EQ setting - something weird like both Ultra Low and Ultra Hi engaged, with a slight boost at 800 on the mid selector. Of course, that was the mid/late 70s, so my memory may not be 100% accurate there! LOL!