ZX Spectrum at 40: a look back

Re:ZX Spectrum at 40: a look back by stewbrew on Saturday February 19, 2022 @11:39AM (#30398366)

Oh come on. The size of the ROM was 16kb. Do you have an idea what is the size of the microcode in your Intel CPU?

I'm sure you could have replaced the chip containing the ROM and replace it with your own version. Things were a little bit more rough back then.

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Re:ZX Spectrum at 40: a look back by razzio on Saturday February 19, 2022 @12:18PM (#30398670)

This is exactly what I did.

I made the ROM writable by soldering a CMOS ram chip across the ROM (was it 16KB?) and any write to the ROM would end up in the RAM. A switch selected either the ROM or RAM to read from. On startup simply copy the ROM to the RAM and flip the switch.

From there on you can read/write the original ROM and modify it to your hearts content.

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