ET4000 weird timings on UniPCemu?

Emulation of old PCs, PC hardware, or PC peripherals.

ET4000 weird timings on UniPCemu?

Postby superfury » 2019-6-22 @ 19:58

I notice that, when running the ET4K in 32K/64K color modes, the vertical timings are correct, but the horizontal timings have some strange kind of (un)centering effect? VGA display modes(640x480x16bpp) and below seem to run without issue. With the higher modes, the video output seems to be correct(active display area), but there's only a little less than half the border/overlay at the right side(the part before horizontal retrace) compared to the left side(the rendering of the remainder of the scanline(after the horizontal retrace) until horizontal total is reached)?

I know that horizontal timing doubling is active for said modes(required for the active display to rendee correctly due to needing double the (attribute 8-bit) bandwidth to fully fetch and render a 15/16-bit pixel, but why is the horizontal timing acting so weird?

VGA_ET4Kdumptxt.zip
ET4K memory data and registers.
(26.21 KiB) Downloaded 8 times

VGA_ET4Kdump.zip
ET4K rendering timings
(13.88 KiB) Downloaded 5 times
superfury
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