ssd hard drive Memory Systems: DRAM, DDR & Memory ControllerIII

SSD hard drive Memory Systems: DRAM, DDR & Memory ControllerIII 1TB SSD drive SSD OEM ssd hard drive system design usually has such a phenomenon SSD hard drive, that is, at the beginning of the designed hard Drive, a system is divided into multiple modules, each module has a clear division of the interface, in addition to the interface is not coupled to each other, but with the improvement of the design, the division of each module is too clear often causes performance bottlenecks, so slowly some modules are put together. There are many reasons to put them together, some for logical reasons and some for physical reasons.

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, that is, at the beginning of the design, a module has more and more functions to complete, it becomes more and more complex, and slowly it is divided into multiple modules, each module completes a sub-function, and interacts with each other through a clear interface.


a system that evolves, the above two phenomena may alternate.


The title of this section is pure nonsense, the 8086 has no memory controller, it only has an access bus, including a control bus, a data bus, and an address bus. For example, a load instruction (a move instruction of 8086 to read data from memory to registers), will read/write the control position on the control bus as a read state, and then put the address where the data to be read on the address bus, and then connect the storage device on the access bus, such as an SRAM, will put data on the data bus (the address bus of 8086 is partially reused with the data bus).

on the 8086, the CPU is integrated with a memory controller that is too simple to be named.

and later the CPU separated some of the functions and established the North Bridge.

the north bridge and CPU are interconnected through a high-speed bus, completing some of the work that is not part of the CPU, but different from conventional peripherals. The difference between the equipment on the North Bridge and the conventional peripherals is mainly the speed.

two necessary functions on the north bridge in general are the display, and the other is the memory controller.

the memory controller on the north bridge receives the fetch instructions sent from the high-speed bus, converts them into DDR instructions on the DDR bus, and completes the access operation.

the fetch instructions coming down from a high-speed bus are usually concise and concise, basically two sentences: read the data on an address to me, and write this data on an address. That is, the load/store directive corresponding to RISC. It does not correspond exactly, because the data to be operated by the load/store instruction is usually 1, 2, 4, or 8 bytes, while the data usually operated on the mem_read/mem _write transactions on the high-speed bus is a Cache line or two Cache lines, and the bytes can also be had (by king off a cache line on other bytes), but not much).

a mem_read, I write is simple, but converted to DDR instructions is more complicated. To consider a variety of different situations, such as open page policy case, row hit does not need to issue active commands, directly send column can be, for example, two addresses consecutively mem_read commands, interpolated in the middle of other commands is not to be out of order to point out, address conversion or not to do, etc. 

the memory controller is a bridge between the two buses.

memory controller involves more electrical technology, such as the correction of DQS signals, but there are also some easier-to-understand algorithms in it, such as page management strategies, reorder buffer design, how to reduce the time spent on refresh, etc.


everyone knows that now the North Bridge is gone, and it goes back to the CPU, so this memory controller also goes back to the CPU and becomes an integrated module, called iMC, that is, the integrated Memory Controller.

its functionality has not changed significantly, but the upstream bus protocol has changed.



can’t remember what else to write about this piece for a while, but you can remind it.

think of FB DIMMs, but feel that the writing is not meaningful, want to know their search information to see it, for example:

OJBK, first send it and then have time to talk about the new storage medium. 1TB SSD drive SSD OEM SSD hard drive