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NTSC Spectrum: Difference between revisions
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Add date code of 6C011E-3 ULA
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One example of an NTSC Spectrum has been found in Chile. As far as is known, it is the same as a [[ZX Spectrum 16k/48k|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 16k/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 (dated 8501 in the example in question) which generates a NTSC frame size and rate. | ||
* One frame lasts 0xe700 (59136) T-states, giving a frame rate of 3.5275×10<sup>6</sup> / 59136 = 59.65 Hz | * One frame lasts 0xe700 (59136) T-states, giving a frame rate of 3.5275×10<sup>6</sup> / 59136 = 59.65 Hz. | ||
* 224 T-states per line implies 264 lines per frame. | * 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. | ||