Model 100
Manuals
RAM
Serial cable
Monoprice 479
The serial port on a Model 100 is wired DTE, the same as a com port on a PC, but with a female connector, which is backwards from anything else. (Though, there is some suggestion that maybe this is actually the original standard, and IBM came along later and changed it by putting male connectors on their PCs.) In any event DTE ports being male is the standard now. Buy any modem or printer or digital scale or any other kind of peripheral with a serial connection, and it will be wired DCE with a female connector, generally 25 pin. Buy any serial port card or usb serial adapter for a pc and it will be wired DTE with a male connector, generally 9 pin.
That means that usually you always need some kind of adapter between a PC and a M100. If you buy a normal null-modem cable, it will most commonly be 9pin female on both ends, because null-modem is used to connect a DTE to another DTE. So you would need to add a 9-to-25 pin adapter, and a gender changer. If you buy a 9pin to 25pin modem cable, that will have the right connectors on both ends, but will be wired straight through. So you would need to add a null-modem adapter, and be careful to get one that has male on one side and female on the other.
This Monoprice 479 cable is "perfect" in that it has the right connectors and wiring, without needing any null-modem or gender changer adapters added, and works with everything in the system rom and all normal software, including telcom, basic, and all tpdd clients.
However one thing it does not do is rts/cts. Those are shorted to self-satisfy on both ends.
No built-in or 3rd party software uses hardware flow control (with one exception). IE there is no way to even set hardware flow control in TELCOM or in BASIC, and no DOS clients use it because the TPDD & TPDD-2 themselves don't.
But the hardware in the M100 can actually use rts/cts if you manipulate the uart yourself from a binary executable (or I suppose, peek/poke from basic). The only software I know of that does this is HTERM. So this cable is NOT good enough for HTERM.
RAM Expansion
ROM Adapters
Pinouts
REX
FigTronix
Molex_Chip_Carrier