English Amiga Board - View Single Post - Video output corruption on Picasso II with 1MB VRAM

superfrog · 18 November 2019, 11:50

Thanks for the explanation. It makes sense that the board allocates the maximum allowable amount of address space, even if not all of it is used. I notice with the Z3 boards that ShowConfig reports explicitly the size of the allocated address space, along with a "subset" value reflecting the actual amount of allocated space that is used by the currently installed VRAM.

With Picasso IV, I notice ShowConfig reports 1 allocated 2meg segment for board with 2 MB configured, and 2 allocated 2meg segments for board with 4 MB configured.

If the display corruption is a consequence of incomplete emulation of how the CL-GD542x chips behave when less than the max usable VRAM is installed, is it unlikely to ever be fixed, or can/will it be fixed at some point?

I only ask because, while it's mostly a non-issue that can be circumvented by simply allocating more RAM to the board, if it's a known issue that will never be fixed, then it should probably be noted in the release notes as a known issue with the emulation of these boards, just to save confusion for anyone who encounters display corruption when running with less than the max usable amount of VRAM. I searched the changelogs and found no such notation.

18 November 2019, 11:50	#3
superfrog Registered User Join Date: Jun 2015 Location: San Francisco, USA Posts: 168	Thanks for the explanation. It makes sense that the board allocates the maximum allowable amount of address space, even if not all of it is used. I notice with the Z3 boards that ShowConfig reports explicitly the size of the allocated address space, along with a "subset" value reflecting the actual amount of allocated space that is used by the currently installed VRAM. With Picasso IV, I notice ShowConfig reports 1 allocated 2meg segment for board with 2 MB configured, and 2 allocated 2meg segments for board with 4 MB configured. If the display corruption is a consequence of incomplete emulation of how the CL-GD542x chips behave when less than the max usable VRAM is installed, is it unlikely to ever be fixed, or can/will it be fixed at some point? I only ask because, while it's mostly a non-issue that can be circumvented by simply allocating more RAM to the board, if it's a known issue that will never be fixed, then it should probably be noted in the release notes as a known issue with the emulation of these boards, just to save confusion for anyone who encounters display corruption when running with less than the max usable amount of VRAM. I searched the changelogs and found no such notation.