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NTSC Spectrum: Difference between revisions
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The '''NTSC Spectrum''' was sold in Chile. It was not sold in the USA as it did not meet FCC regulations<ref>The ZX Spectrum ULA, Chris Smith, 2010, p. 252</ref>. Instead, the [[Timex 2000 series|TS2068]] was produced. | The '''NTSC Spectrum''' was sold in Chile. It was not sold in the USA as it did not meet FCC regulations<ref>The ZX Spectrum ULA, Chris Smith, 2010, p. 252</ref>. Instead, the [[Timex 2000 series|TS2068]] was produced. | ||
One example of an NTSC Spectrum has been found in Chile. As far as is known, it is the same as a normal (PAL) Spectrum with the following differences: | One example of an NTSC Spectrum has been found in Chile. As far as is known, it is the same as a [[ZX Spectrum 48k|normal (PAL) Spectrum]] with the following differences: | ||
* The CPU is clocked at 3.5275 MHz | * The CPU is clocked at 3.5275 MHz | ||
* The ULA is a model 6C011E-3 which generates a NTSC frame size and rate | * The ULA is a model 6C011E-3 which generates a NTSC frame size and rate | ||
* One frame lasts 0xe700 (59136) | * One frame lasts 0xe700 (59136) T-states, giving a frame rate of 3.5275×10<sup>6</sup> / 59136 = 59.65 Hz | ||
* 224 | * 224 T-states per line implies 264 lines per frame. | ||
* The first [[Contended memory|contended cycle]] is at 0x22ff (8959). This implies 40 lines of upper border, 192 lines of picture and 32 lines of lower border/retrace. | * The first [[Contended memory|contended cycle]] is at 0x22ff (8959). This implies 40 lines of upper border, 192 lines of picture and 32 lines of lower border/retrace. | ||
* The contention pattern is confirmed as being the same 6,5,4,3,2,1,0,0 as on the 48K machine. | * The contention pattern is confirmed as being the same 6,5,4,3,2,1,0,0 as on the 48K machine. | ||