On Tue, 14 Jun 2016 10:39:49 +0300, Anssi Saari  wrote:

>Oh? Where do you find that information? The web page
>(http://www.specnext.com/) seems light on the actual specs.

You can find some informations here:
http://www.flickeringmyth.com/2016/05/interview-henrique-olifiers-talks-about-t
he-zx-spectrum-next/

It's an interview of one project's creator.

This is a part:
It’s the HDMI so far, as we have chosen to make it more than just
HDMI. The VGA and RGB outputs present on the Spectrum Next are
produced by the ULA (in our case, the ULAplus) chip originally
powering the Speccy. That’s not compatible with HDMI, as one would
imagine. So we took a Raspberry Pi Zero and connected it via GPIO to
the Next’s expansion port, and monitor the video RAM area for any
changes. When these changes happen, we copy them over to the Pi’s
framebuffer and update what the Pi is outputting via HMDI.

and another interesting one:
The hardest is still to come: using the CPU/GPU/RAM of the Pi Zero
just for HDMI is a waste of resources, so we’ll build drivers to use
them as slave co-processors to the Z80 CPU of the Spectrum Next. That
way the Spectrum can say ‘hey, Pi, render me a 3D OpenGL frame of this
scene, please’, and have that generated and dumped back into the
Speccy RAM for any purpose we want to. So, we could have Minecraft or
Quake for the Spectrum, run on the Spectrum, but accelerated by the Pi
as a worker.

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