The ST506 drive connected to a computer system through a disk controller. A maximum of two disk controller cards could be installed in a standard system. Bad sectors may be detected by the operating system or the disk controller. IBM's original floppy disk controller card also included an external 37-pin D-shell connector. The IWM is essentially a disk controller on one IC. The Altair disk controller occupied two boards and had over 60 ICs. A "disk array controller" name is often improperly shortened to a "disk controller". A single-density disk controller was used to keep costs down. The ASIC acts as a disk controller, plus single-cycle wavetable-lookup synthesizer sound hardware. A redesigned 5-volt disk controller was introduced with its own new Disk BASIC ROM (v1.1). A proper disk controller only allows a "disk" to talk to the same bus. A disk controller could, therefore, transfer data into memory with no load on the processor.