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| Xceed grayscale information |
Posted by: aeberbach on 2020-07-26 07:18:54
I'm curious about how these worked! Since I am probably never going to see on in real life I was hoping to find more information. There's a reference to a homemade grayscale adapter (Gamba's archived page) but I can't find much information on it... how can a board in the PDS slot override the onboard video? Does a Mac so equipped behave as if it has two screens with one disabled, or just one?
Yes I am interested in video hacking and possibly making one.
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Posted by: Trash80toHP_Mini on 2020-07-26 08:50:54
SE/30 Xceed greyscale adapter cloning thread
There's a lot of info there.
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Posted by: Crutch on 2020-07-26 08:55:46
To answer your direct question, an SE/30 so equipped thinks it has one screen, not two with one disabled.
This is a good reference for SE/30 PDS card design (though doesn’t speak specifically to PDS video cards): https://www.vintageapple.org/inside_o/pdf/Designing_Cards_and_Drivers_for_the_Macintosh_Family_3rd_Edition_1992.pdf
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Posted by: Trash80toHP_Mini on 2020-07-26 09:14:49
I'm still curious about the method by which Xceed managed to shut down the onboard video when running in GS mode. Probably in the driver loaded at startup when no sense lines are detected on the external monitor port? When they're detected, the onboard video kicks in as usual. Some kind of Slot Manager trickery must be at play. Can someone with the elusive GS setup run TattleTech to see if it detects the SE/30's video subsystem in slot $E? My guess is that the driver tells the system via Slot Manager routines that there's no Video ROM located there in that hardware state? Can't recall that having been done offhand.
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Posted by: aeberbach on 2020-07-26 09:29:56
Thanks for the pointers - I had not seen that thread. That "Designing Cards..." manual is probably the right place to start.
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Posted by: Trash80toHP_Mini on 2020-07-26 09:46:01
Look at the earlier versions of DCaDftMF for more VidCard development info. The design example appears to be the original "Toby" Frame Buffer card for the Macintosh II. By the third edition it was out of production and can't remember offhand if the references got better or more vague as Apple could no longer supply it to developers. Anyway, ignore the NuBus multiplexing shenanigans and it's the same as a PDS VidCard operationally, just not in interface.
The second and third editions of the DCaD books build upon the first and introduce newer Macs and slot types. They assume an understanding of the previous editions.
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Posted by: maceffects on 2020-07-26 09:54:43
I have some PCBs created from Bolle's design if you need bare Grayscale adapter board.
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Posted by: Crutch on 2020-07-26 10:54:51
Can someone with the elusive GS setup run TattleTech to see if it detects the SE/30's video subsystem in slot $E? My guess is that the driver tells the system via Slot Manager routines that there's no Video ROM located there in that hardware state? Can't recall that having been done offhand. It does not appear to. All I see is the Xceed in slot $9.
A reminder though, the Xceed doesn’t require a driver to work. Is there a means for a PDS card to simply tell the system “I am your main video subsystem”? I’m curious how this works also.
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Posted by: Trash80toHP_Mini on 2020-07-26 10:59:44
Curiouser and curiouser? I have wondered about that on and off for some years. Maybe there's info on the method in the patent filing?
edit: Accelerators tell the PDS they're the main processor by yanking on some signal line or other to turn off the CPU w/o drivers. I imagine a VidCard could do much the same thing to Slot $E video at startup as well? Hadn't known Xceed didn't need drivers to pull off that stunt, curious indeed! Thanks! The DeclROM on any Slot Manager card will have its drivers on board, else the card couldn't come up as the main, or only display at boot.
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Posted by: aeberbach on 2020-07-26 12:27:18
@maceffects thanks but I don't have the video card, so it might not be very useful for me at this point!
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