A dial up controller based modem can be internal or external. Controller based modems are also referred to as hardware modems or hardware controlled modems. Serial modems are also associated with being controller based. Serial modems are so named because that is the port located on the back of the computer that serial modems connect to.
Hardware modems were for a time essential if you lived in a rural area. Dial up internet service providers normally recommend an “external modem”, although they probably mean a “controller based” modem. Dial up ISP’s recommend (and still do) hardware modems because they have a reputation for less disconnects, deal with line noise better, and on average provide a higher dial up connection speed than controllerless and softmodems.
Hardware controlled modems can handle all the telephone signal processing. They don’t need to use other computer resources for help. Earlier home computers didn’t have the processing power of todays. They couldn’t handle multi tasking very well. If you needed to be online while running a high end application or playing online games, your computer would slow down quickly. Its easy to see the advantage of a hardware controlled modem if a situation like this occurred.
Hardware controlled modems can function on computers that have operating systems other than windows installed on them.
I think the single biggest disadvantage associated with a hardware controlled modem is the price. Controller based is the highest performance type of dial up modem. Depending on the manufacturer, a controller based modem can cost upwards of $100. Do some research and decide what sort of modem you want before you buy.