QL Technical Details and Trivia


  • two 128K tape drives (" Microdrives")
  • two joystick/peripheral ports - male DB9
  • an RGB output socket - 7-pin DIN
  • an RF output socket - standard TV aerial type (channel 36 in the UK, channels 3 or 4 in the US)
  • two network ports (called 'QLAN') - 3.5mm jack socket (?)
  • two RS232C-compatible serial ports - female DB9
  • an ROM connector - 28-pin
  • a power supply socket - power supply generates both 9V DC @ 1.8A, and 15.6V AC @ 0.2A

Technical Facts

  • Two main versions of the QL's circuit board were used. The first ones used Issue 5 of the PCB, which had either ROM or EPROM versions with another ROM mounted piggy-backed onto IC33. Later, Issue 6 PCBs were used for volume production which features 48K of on-board ROM which is realised in two Chips: one 32K ROM and one 16K ROM (Minerva uses one 48K ROM). The main differencees are the deletion of IC17 and IC27 and the addition of IC38 (HAL).
  • Built-in networking allows up to 64 QLs to transfer data between themselves, at up to 100K baud




  • The QL's Intel 8049 Intelligent Peripheral Controller chip actually runs at a higher clock speed than the CPU ! (11 MHz versus 7.5 MHz).
  • When connected to a normally-adjusted TV or monitor, the QL's video output would overscan horizontally. This was reputed to have been due to the timing constants in the ZX8301 chip being optimised for the special flat-screen CRT display originally intended for the QL.
  • QLs built by Samsung for export markets had DE-9 sockets for the RS-232 and joystick ports, instead of the unusual and UK-specific BT630W (similar to BS 6312) sockets found on UK-built QLs.
  • External QL Microdrives appeared on QL accessory pricelists but were never produced.
  • While the inexpensive micro-tapes that are used in a Microdrive sound like a good idea, they are limited in speed and data capacity. The tapes are actually tiny continuous loops of high-quality magnetic tape. They contain 200-inches of tape, running at 28 ips (inches per second), making a complete loop in about 7.5 seconds. They hold a maximum of 128K of data, although 100K is more typical. The micro-tapes must be removed when powering the system on or off, otherwise data-loss may occur.
  • When first switched on, the QL asks you which display device you will be using. Pressing F1 uses the RGB monitor connector, while F2 uses the RF output.