This article is a first-hand account of the birth of the UK game development industry through the lens of the rise of Quicksilva, the most successful game development company of the early 1980s. Between 1980 and 1982 Sinclair Research released the ZX80, ZX81 and ZX Spectrum home computers and these supported the nascent game development industry. The market created by the volume of sales of the ZX81 meant that UK game developers could, for the first time, support full time employees through their sales of games. Game developer Quicksilva was one of the first game developers in the UK and this account explains how the UK industry game development industry was improvised into being.
The material for this article is drawn from the personal collection, and recollections, of Mark Eyles, the first employee of Quicksilva.
→ Eyles, Mark. “A first-hand account of Quicksilva and its part in the birth of the UK games industry, 1981–1982.” Cogent Arts & Humanities 3.1 (2016): 1190441.
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I find this really interesting because I know extremely little about ZX-80/ZX-81 games. If I understand correctly, neither could do any CPU processing outside of the vertical display blank … is that right? Here in the USA, that would be a big deal for the Timex-Sinclair equivalents. NTSC vertical blank is much narrower than PAL vertical blank, if you were using 192 active display scan lines.
The ZX80 did the video by having the CPU sitting in a loop scanning the keyboard and triggering video sync and video scanning. To meet the needed bit rate the CPU jumps into the frame buffer and the glue provides NOP statements whilst stealing the data for the video and using it in combination with the Z80 DRAM refresh logic to look up the bit patterns.
The ZX81 added some interrupts to help this process so that you can maintain the video whilst processing although the CPU still spends much of its time unavailable for real work.
There are a few ZX80 action games, they are done by cycle counting the whole damn thing. True masterpieces.
People were able to get various pseudo hires modes out of it by abusing the logic to reset the line counter and point the I register somewhere vaguely useful in the ROM so that you effectively had a choice of 64 1 bit high characters (bit 6 stops the video fetch bit 7 is inverse) in 32 by 192 rows rather than the intended 32x24
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