Originally Posted by wrkalot
Ok, I've answered my own question. Next is to make sure I get the correct cards.
There are 2 card slots on the front of the machine, at the bottom under a panel that runs the length of the box.
Slot 1 is marked "Multi- or Single-Stream CableCARD"
Slot 2 is marked "Single-Stream CableCARD ONLY"
My brain tells me that I can put 1 Multi card in slot one and still record 2 channels at the same time?
Yes, with the HD all you need is one Multi-card and it will service both tuners.
At the time it came out the Multis were just coming into use, so they allowed for use with cable companies who at that time only offered Singles by having two slots.
The original Series 3, the model before the HD, came out before the specs for the Multi-card were finalized, so it turns out that it can't use them, at least not one for both tuners, and has to use 2 Singles*, one for each tuner, but everything after that model can use Multis.
*I may be mistaken and it can use 2 Multis, one for each tuner, but don't know for sure.
Some of the newer TiVos only have one slot because Multis are so prevalent now.