Helped: 26 times Joined: 13 Mar 2006 Posts: 1309 Location: Brigs Lab's
Posted: Tue Aug 04, 2009 7:31 pm
super_spirit wrote:
apakah maksud dari "Reduced (7.8 us), Self-Refresh"
adalah waktu jeda antara tiap waktu "charge" pengisian karena memory ddr bersifat volatile yaitu membutuhkan power terus menerus untuk menyimpan memory. Angka 7.8us atau 64ms ini adalah standardrisasi JEDEC.
Quote:
Typically, manufacturers specify that each row should be refreshed every 64 ms or less, according to the JEDEC (Foundation for developing Semiconductor Standards) standard. Refresh logic is commonly used with DRAMs to automate the periodic refresh. This makes the circuit more complicated, but this drawback is usually outweighed by the fact that DRAM is much cheaper and of greater capacity than SRAM. Some systems refresh every row in a tight loop that occurs once every 64 ms. Other systems refresh one row at a time — for example, a system with 213 = 8192 rows would require a refresh rate of one row every 7.8 µs (64 ms / 8192 rows). A few real-time systems refresh a portion of memory at a time based on an external timer that governs the operation of the rest of the system, such as the vertical blanking interval that occurs every 10 to 20 ms in video equipment. All methods require some sort of counter to keep track of which row is the next to be refreshed. Most DRAM chips include that counter; older kinds require external refresh logic to hold that counter. (Under some conditions, most of the data in DRAM can be recovered even if the DRAM has not been refreshed for several minutes. See dynamic random access memory#Security.)
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