I am creating a custom CPU on the Nexys 4 DDR. At 100 MHz system clock, it executes commands at about 20 MIPS on average. I used async SRAM in past, this was a piece of cake as the SRAM was always faster than my CPU. But now, being on the Nexys 4 DDR, I'd like to leverage the on board DDR RAM.
Having a look at Mihaita Nagy's DDR to SRAM component (link: https://reference.digilentinc.com/nexys4-ddr:sram) I was a bit surprised: On the reference page you can read, that an async. read operation of a single data word takes 210ns. Is this realistic or maybe a typo? 210ns means that the max read speed would be 4,76 MHz. This seems to slow to be true. So did I maybe get something wrong (I am a pretty new to DDR RAM topics therefore this might be the case). If I did not get it wrong: Just being curious: Why is it so slow?
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sy2002
Hi all,
I am creating a custom CPU on the Nexys 4 DDR. At 100 MHz system clock, it executes commands at about 20 MIPS on average. I used async SRAM in past, this was a piece of cake as the SRAM was always faster than my CPU. But now, being on the Nexys 4 DDR, I'd like to leverage the on board DDR RAM.
Having a look at Mihaita Nagy's DDR to SRAM component (link: https://reference.digilentinc.com/nexys4-ddr:sram) I was a bit surprised: On the reference page you can read, that an async. read operation of a single data word takes 210ns. Is this realistic or maybe a typo? 210ns means that the max read speed would be 4,76 MHz. This seems to slow to be true. So did I maybe get something wrong (I am a pretty new to DDR RAM topics therefore this might be the case). If I did not get it wrong: Just being curious: Why is it so slow?
Are there faster ways to work with the DDR RAM?
Thank you and best regards
Mirko
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