longboard Posted May 7, 2019 Share Posted May 7, 2019 Hello, In section 3 of the user manual for my Nexys A7 FPGA development board there is the following statement regarding the 2 external memories... "1Gib (128MiB) DDR2 SDRAM and a 128Mib (16MiB) non-volatile serial Flash device" I don't completely understand the specs in parenthesis? I think they may refer to configurations within the memory ICs themselves. For instance... for the DDR2 SDRAM, PN: MT47H64M16HR-25E I looked at the data sheet and saw the following configuration option listed... 128 Meg x 8 (16 Meg x 8 x 8 banks) So I just wanted to try and better understand these specs for the on board memory. thank you -Sean Link to comment Share on other sites More sharing options...
D@n Posted May 7, 2019 Share Posted May 7, 2019 @longboard, Yeah, that's really confusing isn't it? At issue is the fact that many of these chips are specified in Mega BITS not BYTES. So the 1Gib is mean to refer to a one gigabit memory, which is also a 128 megabyte memory. That's what the parentheses are trying to tell you. Where this becomes a real problem is that I've always learned that a MiB is a reference to a million bytes, 10^6 bytes, rather than a mega byte, or 2^20 bytes. The proper acronyms, IMHO, should be Gb, GB, Mb, and MB rather than GiB or MiB which are entirely misleading. As for the memory, listed as 16 Meg x 8 x 8, that's a reference to 8-banks of 16-mega words or memory, where each word is 8-bits wide. In other words, the memory has 16MB*8 or 128MB of storage. You could alternatively say it had 1Gb of memory, which would be the same thing, but this is often confused with 1GB of memory--hence the desire for the parentheses again. Dan Link to comment Share on other sites More sharing options...
longboard Posted May 8, 2019 Author Share Posted May 8, 2019 Thank you Dan. Your answer helps clarify things greatly for me on this subject. I appreciate you taking the time to help me out. -Sean Link to comment Share on other sites More sharing options...
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longboard
Hello,
In section 3 of the user manual for my Nexys A7 FPGA development board there is the following statement regarding the 2 external memories...
"1Gib (128MiB) DDR2 SDRAM and a 128Mib (16MiB) non-volatile serial Flash device"
I don't completely understand the specs in parenthesis? I think they may refer to configurations within the memory ICs themselves.
For instance... for the DDR2 SDRAM, PN: MT47H64M16HR-25E I looked at the data sheet and saw the following configuration option listed...
128 Meg x 8 (16 Meg x 8 x 8 banks)
So I just wanted to try and better understand these specs for the on board memory.
thank you
-Sean
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