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ZX Spectrum 128: Difference between revisions
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Document 128K HAL faults
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(Document 128K HAL faults) |
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| || || Disable Paging || ROM Bank || Active Screen || colspan="3" | RAM Bank | | || || Disable Paging || ROM Bank || Active Screen || colspan="3" | RAM Bank | ||
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Due to a bug either in the 128K's HAL10H8 chip or in the 128K PCB, memory banks 1, 3, 5 and 7 are contended (and the rest uncontended) as opposed to 4, 5, 6 and 7 as documented in the service manual. The +2 (with grey case) shares this fault, although it has been reported that later Spanish +2s were shipped with an updated HAL chip, which may have fixed this problem. | |||
Reads from port 0x7ffd cause a crash, as the HAL does not distinguish these from writes, resulting in a floating data bus being used to set the paging registers. | |||
==Keypad== | ==Keypad== | ||