Fanuc 3M drip feed (DNC) conversion chips can be purchased from fanuc3mdripfeed.com for the lowest price anywhere I know; a little over $900. The price also includes chip sockets so inserting them into your main board is much easier, as well as a chip extractor for your old chips. They even include an anti-static wrist-band for goodness sake! Although they advise using someone conversant in handling electronics, their "Upgrade Instructions" and pictures take you step by step through the process and then go on to tell you how to use your new DNC ability. And before anyone asks me..... you DON'T need a tape reader on your machine.
But make sure you send your board number to them before purchase so you can be sure you get the right set of chips (it is located on the top right of your board) Their website even gives a picture of where it is. In fact the website gives a picture of everything, even including the direction the chips should be inserted and other potential pitfalls for the novice.
The site seems to be exclusively set up for Fanuc 3M drip feed conversions/upgrades for DNC control (as its web name suggests). Anyone considering adding DNC ability to their old Fanuc 3M should check it out before any decision is made. The other option is to buy a new machine. But you will not get much more by this cheap upgrade as your machine will have unlimited memory and 3D machining from your PC.
You might wonder how I know all this? I guess I'm still miffed that Fanuc tried to screw me with a new CNC machine when they must have known full well that this upgrade was available! I may not have a new machine, but for about $900 I obtained 3D machining, unlimited memory, unlimted program sizes, DNC (drip feed) and a control that can handle the latest CAD/CAM software. (= one black eye for Fanuc Corp!)