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Altera_Forum
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21 years ago

DDR vs. SDR RAM...

Anyone know if DDR Ram will fare better with the NiosII data master than SDRAM? After Dirk figured out it takes a whopping 12 clocks @50MHz (~240ns) per SDRAM read when not using the dma, we re...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
21 years ago

Hi Thomas,

Are you saying Jesse's time table doesn't apply to onchip RAM? He didn't qualify it as such. If it does apply then onchip reads should be 7 clocks. (I would expect the LDxIO instructions to do it in 6 or even 5 if they can also skip the align) So dma'ing to onchip seems of little help unless that onchip ram is the cache itself.

I&#39;ve thought/wondered about a custom instruction interface to bypass the Avalon bus. I&#39;m not sure how or if it would be integrated into the memory map, but even if it was a rogue interface it would be well worth it to gain 1 clock access at least to onchip ram. Maybe a smart guy like you could do this http://forum.niosforum.com/work2/style_emoticons/<#EMO_DIR#>/smile.gif

Ken