Are RDP Color Combiner registers readable?

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Narann
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Are RDP Color Combiner registers readable?

Post by Narann » Wed Oct 21, 2015 9:21 pm

An easy one:

Does the GBI provide a way to read RDP Color Combiner registers? Or does the RDP Color Combiner registers were write only? :roll:

Thanks in advance!

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MarathonMan
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Re: Are RDP Color Combiner registers readable?

Post by MarathonMan » Wed Oct 21, 2015 11:25 pm

If you can't access them via the instructions, then no: http://hcs64.com/files/RDP_COMMANDS.pdf

I'm pretty sure you can't, but I haven't worked with the instruction set recently or long enough to confirm without looking in the above doc. (EDIT: Nope, the RDP only has set combine mode. Once you execute the instruction, the combined registers latch the values and you have no way of reading them back out).

Soooo...

EDIT: Did you really mean GBI? If so, you can always grab it back out from the display list command... just follow the display list. Once the memory for the display list is repurposed, then the above applies.

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Narann
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Re: Are RDP Color Combiner registers readable?

Post by Narann » Thu Oct 22, 2015 10:02 am

Thanks!

This is important because it mean, except the RDP it-self, nothing else access to thoses values, meaning I can organize them in an arbitrary way.

angrylion plugin seems to doesn't care about RDP input alignment too.

Make the RDP color registers in read only make sense from an API design stand point: You don't want your users to decrease performances dealing with get instructctions everywhere.

I already think it was like this but having no knownledge in any other N64 component (RSP, R4300i), I was not sure.
MarathonMan wrote:EDIT: Did you really mean GBI? If so, you can always grab it back out from the display list command... just follow the display list. Once the memory for the display list is repurposed, then the above applies.
Not sure about what you say but, but if you say I can parse the value my-self then yes, this is what I do! I create a 32 bits pointer on DPC_START_REG and move forward until DPC_END_REG, "binary parsing" every commands to get the raw datas.

Thanks again! :)

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MarathonMan
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Re: Are RDP Color Combiner registers readable?

Post by MarathonMan » Thu Oct 22, 2015 9:41 pm

GBI is the just binary interface that Nintendo designed (hence, graphics binary interface) for graphics commands.

They are often high level abstractions of either transform operations (which get executed on the RSP) or RDP instructions.

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Narann
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Re: Are RDP Color Combiner registers readable?

Post by Narann » Fri Oct 23, 2015 12:49 am

MarathonMan wrote:They are often high level abstractions of either transform operations (which get executed on the RSP) or RDP instructions.
I'm not a LLE or Cycle Accurate expert but from what I can see from the RDP commands, GBI look very close from the metal.

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MarathonMan
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Re: Are RDP Color Combiner registers readable?

Post by MarathonMan » Fri Oct 23, 2015 11:18 am

The RDP ones likely are, but the transform commands in the GBI are basically operations/parameters for the ucodes.

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