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Brain dump thread on some troubles I'm having with MAME's emulationg of the TurboGX graphics board for Sun4 workstations. [thread]

TurboGX/cgsix works "well enough" with SunOS 4.1.1 - there are some minor glitches, but otherwise it looks mostly indistinguishable from a bwtwo board, so that's good.

On the other hand, the way the Solaris 2.5.1 installer behaves can be best described as "downright bizarre". For one thing, the moment it starts up OpenWindows, it uploads a palette consisting of exactly one white entry and 255 black entries.

It then draws two logos using numerous different palette entries. Now, I'm not racist, but I have to assume that Sun's engineers at the time wanted actual logos to appear, and not two black rectangles.

Compounding the issue is that I strongly suspect I know why it's not uploading the correct palette, but I can't quite work out which IRQ line on the SPARC an SBus interrupt is supposed to pull.

I have some vague docs that say that palette uploads should be done during V-sync in order to prevent tearing, and which specify that this should be done by enabling V-sync IRQs, then waiting for the IRQ to trigger.

However, I have other documentation from BitSavers which has a penned-in note saying that IRQ 8 is for "video". If I trigger IRQ 8, then the Solaris 2.5.1 installer explodes with a repeating error message about an unexpected IRQ.