The Leader in Memory Technology

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Arnold Byrd
3 years ago
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What type of reader reads from a row?
What is the main point of note 1?

1 DDR SDRAM s 2 ; Basic DDR SDRAM operations 1. DDR SDRAM application notes available from Samsung - App. note 1 : Key features and points for memory controller designers ; Explains key features of DDR SDRAM and points which users need to pay attention onto. - App. Note 2 : Basic DDR SDRAM operations ; Examples of consecutive commands such as read-read, read-write and write-read. Explain when we can do gapless operation and when we need to put a dead cycle or cycles. 2. Contents This note is intended to explain what happens in case of consecutive DDR SDRAM accesses. - Read followed by a read - Read followed by a write - Write followed by a write - Write followed by a read For all the above four patterns, the following three cases are explained. - Page Hit to the same page - Row Empty to the same Row, but a different Bank - Row Empty to a different Row

Note 2 : Basic DDR SDRAM operations ; Examples of consecutive commands such as read-read, read-write and write-read.

2 Terminology The following terms are used in this material. To avoid confusion, please refer to the following definitions for each term Page Hit: Access to an already opened page Target page is already activated before access. Row Empty: Access to a closed page Target page is in precharge. Row: Means external bank Controlled by CS# in system. One DIMM can have more than one Row Bank: Means internal bank inside DDR SDRAM. Controlled by Bank Address. DDR SDRAM has four internal banks Row Address: ddress for DDR SDRAM

page is already activated before access. Row Empty: Access to a closed page Target page is in precharge.

3 Page Hit to the same page Read-to-Read (1/3) CL=2, BL=4 Read A Read B Read C s a1 a2 a3 a4 b1 b2 b3 b4 c1 c2 c3 Read from one row address, then Read from the same page

4 Read-to-Read (2/3) Row Empty to the same Row, but a different Bank CL=2, BL=4 BA1 Read BA2 Read BA1 BA3 Read BA2 s a1 a2 a3 a4 b1 b2 b3 b4 c1 Read from a Bank, then Read from another bank in the same row

5 Read-to-Read (3/3) Row Empty to a different Row CL=2, BL=4,, BAx Read BAx, BAx Read BAx,,BA2 s Dead a1 a2 a3 a4 b1 b2 b3 b4 Window Read from a Row, then Read from another Row

6 Read-to-Write (1/3) Page Hit to the same page CL=2, WL=1, BL=4 Read Write s Dead r1 r2 r3 r4 w1 w2 w3 w4 Window Read from one row address, then Write to the same page

7 Read-to-Write (2/3) Row Empty to the same Row, but a different Bank CL=2, WL=1, BL=4 Read BA3 WR BA3 s r1 r2 r3 r4 Dead Window w1 w2 w3 w4 Read from a Bank, then Write to another bank in the same row

8 Read-to-Write (3/3) Row Empty to a different Row CL=2, WL=1, BL=4, BAx Read BAx, BAx WR BAx s Dead r1 r2 r3 r4 w1 w2 w3 w4 Window Read from a Row, then Write to another Row

9 Write-to-Write (1/3) Page Hit to the same page WL=1, BL=4 Write A Write B Write C Write D s a1 a2 a3 a4 b1 b2 b3 b4 c1 c2 c3 c4 d1 d2 Write to one row address, then Write to the same page

10 Write-to-Write (2/3) Row Empty to the same Row, but a different Bank WL=1, BL=4 BA1 WR WR BA1 BA2 WR BA2 s a1 a2 a3 a4 b1 b2 b3 b4 c1 c2 c3 Write to a Bank, then Write to another bank in the same row

11 Write-to-Write (3/3) Row Empty to a different Row WL=1, BL=4, BAx, BAx WR BAx WR BAx s a1 a2 a3 a4 c1 c2 c3 c4 Write to a Row, then Write to another Row

12 Write-to-Read (1) Page Hit to the same page CL=2, WL=1, BL=4 WR Read twr= 2 clocks s w1 w2 w3 w4 Dead Window r1 r2 Write to one row address, then Read from the same page

13 Write-to-Read (2) Row Empty to the same Row, but a different Bank CL=2, WL=1, BL=4 WR BA3 Read BA3 twr= 2 clocks s w1 w2 w3 w4 Dead Window r1 r2 Write to a Bank, then Read from another bank in the same row

14 Write-to-Read (3) Row Empty to a different Row CL=2, WL=1, BL=4 WR BAx BA3 Read BAx twr= 2 clocks s Dead w1 w2 w3 w4 r1 r2 r3 Window r4 Write to a Row, then Read from another Row

Computer Architecture

Computer Architecture Random Access Memory Technologies 2015. április 2. Budapest Gábor Horváth associate professor BUTE Dept. Of Networked Systems and Services ghorvath@hit.bme.hu 2 Storing data Possible

The Leader in Memory Technology

What type of reader reads from a row?

What is the main point of note 1?