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To: Randall Hopper <rhh@ct.picker.com>
cc: Doug White <dwhite@resnet.uoregon.edu>, multimedia@freebsd.org
Subject: Re: Updated driver (bt848-970424) 
In-reply-to: Your message of "Thu, 01 May 1997 07:05:21 EDT."
             <19970501070521.63393@ct.picker.com> 
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Date: Thu, 01 May 1997 16:06:28 -0700
From: Amancio Hasty <hasty@rah.star-gate.com>
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>From The Desk Of Randall Hopper :
> 
> Ahhh, I think I know what's going on now.  The Bt's 4Bpp format w/ no byte
> swapping is: ARGB.  With byte swapping, you get access to BGRA, GBAR, and
> RABG.  According to your visual's RGB masks (RGB: 0000FF,00FF00,FF0000) and
> display frame buffer depth (4Bpp), seems you need an ABGR ordering.  The Bt
> can't do it, thus the drop-back to X images.  Sorry about that.
> 
> If the Mach64 server support changing the pixel component ordering for that
> 4Bpp/24bpp mode to ARGB (I know the chip supports it at least), that should
> get you going there.  Otherwise 15/16bpp might be your best option.
> 
> Randall

Also, if the X server supports 24bit then the Bt848 can do BGR and drop
the "A". This can be done by setting the PCI Enable Bytes on the Write
Risc Instructions . PCI Enable Bytes is field 15:12 . In this case set the 
Bt848 to output 32bit , word swap, byte swap, and set bit 12.

I don't think that Mach64 supports 24bit. Nevertheless, we should plan
to incorporate the PCI Enable Bytes feature.

	Enjoy,
	Amancio