![]() Overclocking the i.MX6S-system to 32-bit DDR3-1066 or underclocking the i.MX6D/Q-system to 64-bit DDR3-800 results in pretty much identical performance values. The same benchmark running on a single core on our i.MX6D/Q-systems with 64-bit DDR3-1066 RAM shows another ~10-20% performance increase, which seems to be caused by the higher DDR3 clock (533 MHz instead of 400 MHz). (Maybe also again limited by the SoC-internal AXI-bus on i.MX6S?! Can't find any documentation on the internal bus-speeds in i.MX6-series.) Running the same benchmark on our i.MX6S-system with 32-bit DDR3-800 we measure for all tests ~10-20% higher performance, which probably can be explained by the more efficient out-of-order Cortex-A9 core compared to the in-order Cortex-A8 in i.MX53. 1.4 GB/s when two DDR3 memory banks on two different chip-selects are used (tested on Freescale's i.MX53 QSB board).1.2 GB/s when two different DDR3 memory banks on the same chip-select are involved. ![]() 0.9 GB/s when only a single DDR3 memory bank is involved.We're using hand-tuned assembler-code memset() and memcpy() functions for benchmarking, using only ARMv7 integer code (no NEON), which match up quite nicely with theoretical bandwidth values on Freescale's i.MX53 QSB board and our own i.MX53-board designs with 32-bit DDR3-800 RAM, which we used for comparison to our i.MX6-design: While DDR3-800 provides a (very) theoretical bandwidth of 3.2 GB/s, the i.MX53-SoC's internal 200 MHz, 64-bit (single-datarate) AXI-bus connecting the Cortex-A8 core to the RAM-controller apparently limits the bandwidth already to 1.6 GB/s and our benchmark actually measures While all combinations realized so far (i.MX6Q and i.MX6D with 64-bit DDR3-1066, and i.MX6S with 32-bit DDR3-800) work fine, all memory configurations are working stable, entire memory can be accessed properly, Freescale's DDR3 Stress Test tool runs fine just as well as more elaborate custom RAM tests and all three OSses, we can't seem to find any performance difference between 64-bit and 32-bit DDR3 configurations. We're currently porting Linux, Android, and Windows-CE BSPs to our own i.MX6-based board series, which can be equipped with either i.MX6Q, i.MX6D, i.MX6DL or i.MX6S SoCs, and either 32-bit or 64-bit DDR3 RAM in DDR3-800 and DDR3-1066 configurations connected to a single chip-select.
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