16-bit bus), a 12 or 24 MB, 14-inch Shugart SA-4000-series hard disk, and an 8-inch floppy disk drive. The internal layout of the PERQ 1 was dominated by the vertically mounted hard disk drive. It was largely this that determined the height and depth of the chassis. A basic PERQ 1 system comprised a CPU board, a memory board (incorporating the framebuffer and monitor interface) and an I/O board (IOB, also called CIO). The IOB included a Zilog Z80 microprocessor, an IEEE-488 interface, an RS-232 serial port, hard and floppy disk interfaces and speech synthesis hardware. PERQ 1s also had a spare Optional I/O (OIO) board slot for additional interfaces such as Ethernet. A graphics tablet was standard. Most PERQ 1s were supplied with an 8½ ×11-inch, 768×1024 pixel portrait orientation white phosphor monochrome monitor. PERQ 2 The PERQ 2 (codenamed Kristmas during development) was announced in 1983. The PERQ 2 could be distinguished from the PERQ 1 by its wider, ICL-designed cabinet, with a lighter-coloured fascia, vertical floppy disk drive and three-digit diagnostic display. The PERQ 2 used the same 16k WCS CPU as the PERQ 1A and had a 3-button mouse in place of the graphics tablet. It was configured with a quieter 8-inch 35 MB Micropolis Corporation 1201 hard disk, 1 or 2 MB of RAM and had the option of the PERQ 1's portrait monitor or a 19-inch, 1280×1024 landscape orientation monitor. Due to manufacturing problems with the original 3RCC PERQ 2 (also known as the K1), ICL revised the hardware design, resulting in the PERQ 2 T1 (or ICL 8222). The later PERQ 2 T2 (ICL 8223) and PERQ 2 T4 models replaced the 8-inch hard disk with a 5¼-inch hard disk, which also allowed for a second disk to be installed internally. The T4 model (of which only around 10 are thought to have been produced) had an extended 24-bit CPU and backplane bus, allowing the use of a 4MB RAM board. The PERQ 2 retained the PERQ 1's OIO slot, but replaced the IOB with either an EIO (Ethernet I/O) or NIO (Non-Ethernet I/O) boards. These were similar to the IOB, with the addition of a non-volatile real-time clock, a second RS-232 port, and (on the EIO board) an Ethernet interface. PERQ 3 The PERQ 3A (otherwise known as the ICL 3300 Advanced Graphics Workstation) was developed by ICL as a replacement for