Hicolour
Several third-party Spectrum clones, including the Timex Sinclair machines and the Pentagon, support a screen mode in which attribute blocks are 8x1 pixels in size rather than the usual 8x8. A screen in this mode takes 12 KB RAM. In the case of the Timex, this mode is activated through the command OUT 255,2. In addition, this screen mode can be generated through the use of the MB-02 disk system's DMA hardware (where the technique is known as Multitech), and is also available as Mode 2 on the SAM Coupé.
Read more about this topic: ZX Spectrum Graphic Modes