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SiriusHardware · 1st Jun 2020, 7:07 pm

Thanks for pointing out the little problem with NRDS /OE, I probably would have overlooked that.

If I did set about programming a PROM as the address decoder would it be worth trying to map the 'lost' 0.5K somewhere else? I don't think there are any other handy 'holes' in the memory map to drop RAM into, are there - if there were, nobody would go to all the trouble to free up 0200-07FF, they'd just use a hole that was already there?

The PROM isn't the only thing which originally has images but I think some of the original software may depend on the the images existing so that it can reach into two areas with a pointer placed on the boundary.

Despite that, I think forum user 'circuitryboy' did go the extra mile and added mods to remove the other images as well so that RAM could be mapped into those areas.

1st Jun 2020, 7:07 pm	#16
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 11,569	Re: MK14 memory upgrade Thanks for pointing out the little problem with NRDS /OE, I probably would have overlooked that. If I did set about programming a PROM as the address decoder would it be worth trying to map the 'lost' 0.5K somewhere else? I don't think there are any other handy 'holes' in the memory map to drop RAM into, are there - if there were, nobody would go to all the trouble to free up 0200-07FF, they'd just use a hole that was already there? The PROM isn't the only thing which originally has images but I think some of the original software may depend on the the images existing so that it can reach into two areas with a pointer placed on the boundary. Despite that, I think forum user 'circuitryboy' did go the extra mile and added mods to remove the other images as well so that RAM could be mapped into those areas.