use 64 KB of the standard machine's 128 KiB of RAM and there is no support for this feature in the QL's original firmware. The alternative and improved operating system Minerva provides full support for the second frame buffer. When connected to a normally-adjusted TV or monitor, the QL's video output overscans horizontally. This is reputed to have been due to the timing constants in the ZX8301 chip being optimised for the flat-screen CRT display originally intended for the QL. Internally, the QL comprises the CPU, two ULAs (ZX8301 and ZX8302) and an Intel 8049 microcontroller known as the IPC, or "Intelligent Peripheral Controller", responsible for keyboard, joystick ports, RS-232 inputs and sound output. The ZX8301 or "Master Chip" implements the video display generator and also provides DRAM refresh. The ZX8302, or "Peripheral Chip", interfaces to the RS-232 ports (transmit only) Microdrives, QLAN ports, real-time clock and the 8049 via a synchronous serial link. The 8049 included at a late stage in the QL's design (the ZX8302 originally being intended to perform its functions) runs at 7.5 MHz and acts as a keyboard/joystick interface, RS-232 receive buffer and audio generator. When comparing technical specifications among microcomputers in the traditional sense of the term, the QL qualifies as the fastest for having a 15 MHz clock that alternates between Motorola's 68008 & Intel's 8049. Two built-in Microdrive tape-loop cartridge drives provide mass storage, in place of the more expensive floppy disk drives found on similar systems of the era. Microdrives had been introduced for the ZX Spectrum in July 1983, although the QL uses a different logical tape format. Interfaces include an expansion slot, ROM cartridge socket, dual RS-232 ports, proprietary QLAN local area network ports, dual joystick ports and an external Microdrive bus. The QL uses British Telecom type 631W plugs of similar design to British telephone sockets for serial cables except for QLs built by Samsung for export markets, which have DE-9 sockets. Joysticks connect to the QL with similar type 630W plugs. Physically, the QL is the same black colour as the preceding ZX81 and ZX Spectrum, but introduced a new angular styling theme and keyboard design which would later be seen in the ZX Spectrum+. QDOS, a pre-emptive multitasking operating system primarily designed by Tony Tebby, is included on ROM, as is an advanced structured BASIC interpreter, named SuperBASIC designed by Jan Jones, which is also used