Reply to post: Re: What we need

ZX Spectrum reboot latest: Some Vega+s arrive, Sky pulls plug, Clive drops ball

Dan 55 Silver badge

Re: What we need

the 2MHz 6502 in the BBC performed tasks faster than the 3.75 MHz in a Spectrum.

The memory access was also more simple for 6502, which enabled it to work with slower memory than the Z80, mainly because memory and CPU clock speeds were linked together.

The BBC had 4Mhz memory multiplexed between the 2Mhz CPU and the video display, so the CPU always never had to wait to access the memory.

The Electron on the other hand had the same 2Mhz CPU but used a contended memory model (similar to the Spectrum). When the video output needed to access the memory, the CPU was paused. On the Electron this meant the machine was pretty slow, far slower than BBC and slower the Spectrum. Unlike the Spectrum, it had no uncontended RAM area.

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