Re: Notes on netwinder frame buffer performance
>When a cacheline writes to the cyberpro the first 32 bit word gets
>written correctly, the next 3 do not make it into the frame buffer.
>
>In this state caching is not possible for the framebuffer. If the
>DEC21285 can be convinced not to do burst writes (thats a guess) or
>the CyberPro 2000 can be convinced to accept them then we could turn
>on caching and have much better performance.
I suspect this isn't possible. From what I remember of the 21285 manual it
says fairly unequivocally that you must not enable caching for areas other
than ROM and SDRAM. My guess is that the Footbridge doesn't understand burst
writes to its PCI direct master regions and is discarding all but the first
cycle.
>Does anyone here have a contact at iGS Technologies?
Yes, I've dealt with them in the past. I will look the details up for you
next time I am in the office.
p.
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