Yea, it's something I picked up a while back. It's nice when you just want to talk to something without having to program a micro controller to do it.

Just following up here finally.
The cable-modem reflashing experiment has been a decent success, with over 30 modems repaired to date. Things seem to be tapering off now finally, which is a bit of a shame. For every modem that "finds me", there are about 100 affected ones that don't. Those unfortunate ones most likely end up getting junked.

Here's the latest version of the flashing rig, totally standalone and turn-key. Just hook it up to the modem, plug the modem's PSU into the rig, and watch the blinkin' LEDs.

Well done Mark! Thanks for keeping those 30 modems out of the landfill. Hopefully, many more will come your way.

After updating around 50 or so modems, I finally soldered up a couple of the rigs. One went to a friendly ISP, who traded a DOCSIS 3.0 cable modem for it. The other continues to be used here, about once a week or so now. Over 60 modems re-flashed to date.

This one used a fancier SD-Card adapter from an eBay seller ($1.80 or so). I later discovered the surplus 3.3V regulator on the SD-Card adapter was sucking power like mad, and so removed it.