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Qsys with up to 8 GB of DDR2

Honored Contributor II

Hi all, 


Im developing an application that requires more than 1G DDR2 memory, but I cant use it direct on Qsys because Avalon address is restricted to n^31. I'm developing on Stratix IV FPGA (Terasic DE4). 


I would like to know with any of you have already face this problem and how can I handle this on the best way. 


Best regards, 


Rafael C.
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Honored Contributor II

Although I haven't done this on the Stratix 4 board yet (haven't needed that much memory yet), you can use the AXI bus in QSYS and get up to a 64 bit address space. 


I have used AXI with the Cyclone V SOC kit, and with the Xilinx Zync platform, and it's a powerful bus interface. The Problem is this doesn't seem to be supported by NIOS II yet. (Only 32 bit CPU, so it's tough to address > 4 GB) 


The best solution I guess is dependent on your real requirements. If you need it for code space you can do blocks of memory, but it's a pain to manage. If you need it for physical data space for the rest of the hardware, you can create a custome interface, that gives avalon access to 2GB, and the hardware the the rest of your FPGA hardware the rest. 


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