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Embedded Software for SoC - Grupo de Mecatrônica EESC/USP

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SDRAM-Energy-Aware Memory Allocation 327<br />

dynamic energy. At the same time, the static energy consumption slightly<br />

reduces since less misses results in a shorter execution time (see the static<br />

energy of the example in Figure 24-2 executed at 600 MHz.).<br />

However, when extra banks do not significantly reduce the page-miss rate<br />

anymore, the dynamic energy savings become smaller than the extra static<br />

energy nee<strong>de</strong>d to keep the banks in CS/STBY-mo<strong>de</strong>. The total energy consumption<br />

increases then again. A nice illustration of this is Quick24to8 in<br />

Table 24-5. The total energy consumption <strong>de</strong>creases up to three banks and<br />

then increases again due to the extra static energy. Also, in Figure 24-2. the<br />

total energy consumption increases again when more than five banks are used.<br />

From these examples, we see that an optimal number of active banks exist.<br />

The optimal number of banks <strong>de</strong>pends on the ratio of static versus dynamic<br />

energy. When the banks become more active (e.g. because more tasks are<br />

activated or the processor frequency is increased), the dynamic energy<br />

becomes more important than the static energy and the optimal number of<br />

Please<br />

check<br />

no. of<br />

figures<br />

and<br />

no. of<br />

tables<br />

Table 24-5. Energy comparison of several allocation strategies.<br />

Tasks (100 Mhz)<br />

Nds<br />

1<br />

2<br />

3<br />

4<br />

5<br />

6<br />

Fir+Conv(SA)<br />

Fir+Conv(MA)<br />

Fir+Conv(RA)<br />

Fir+Conv(GP)<br />

Fir+Conv(BE)<br />

R2Y+Cmp(SA)<br />

R2Y+Cmp(MA)<br />

R2Y+Cmp(RA)<br />

R2Y+Cmp(GP)<br />

R2Y+Cmp(BE)<br />

R2Y+Cmp+Conv(SA)<br />

R2Y+Cmp+Conv(MA)<br />

R2Y+Cmp+Conv(RA)<br />

R2Y+Cmp+Conv(GP)<br />

R2Y+Cmp+Conv(BE)<br />

R2Y+Cmp+Conv+Dct(SA)<br />

R2Y+Cmp+Conv+Dct(MA)<br />

R2Y+Cmp+Conv+Dct(RA)<br />

R2Y+Cmp+Conv+Dct(GP)<br />

R2Y+Cmp+Conv+Dct(BE)<br />

Fir+Conv(SA)<br />

Fir+Conv(MA)<br />

Fir+Conv(RA)<br />

Fir+Conv(GP)<br />

Fir+Conv(BE)<br />

7<br />

7<br />

7<br />

7<br />

7<br />

8<br />

8<br />

8<br />

8<br />

8<br />

12<br />

12<br />

12<br />

12<br />

12<br />

18<br />

18<br />

18<br />

18<br />

7<br />

7<br />

7<br />

7<br />

7<br />

_<br />

20958<br />

20958<br />

–<br />

20958<br />

–<br />

4986<br />

4986<br />

–<br />

4986<br />

–<br />

23531<br />

23531<br />

–<br />

23531<br />

–<br />

26195<br />

26195<br />

–<br />

26195<br />

—<br />

20480<br />

20480<br />

–<br />

20480<br />

20993<br />

9858<br />

15712<br />

20993<br />

10250<br />

4859<br />

3832<br />

4362<br />

4859<br />

4041<br />

–<br />

13872<br />

13872<br />

–<br />

13769<br />

–<br />

16684<br />

21896<br />

–<br />

16212<br />

20305<br />

9261<br />

14938<br />

20305<br />

9526<br />

20993<br />

9269<br />

13834<br />

9943<br />

9269<br />

4859<br />

1877<br />

3733<br />

3821<br />

2031<br />

24082<br />

12456<br />

12456<br />

24082<br />

13468<br />

–<br />

15165<br />

19332<br />

–<br />

16143<br />

20305<br />

7582<br />

11664<br />

8395<br />

8219<br />

20993<br />

8641<br />

12381<br />

8641<br />

9515<br />

4859<br />

1521<br />

3407<br />

1521<br />

1553<br />

24082<br />

11392<br />

11392<br />

13034<br />

11515<br />

26647<br />

13665<br />

17947<br />

26647<br />

14224<br />

20305<br />

6600<br />

11421<br />

7842<br />

7623<br />

20993<br />

8641<br />

12436<br />

8641<br />

8942<br />

4859<br />

1521<br />

3368<br />

1521<br />

1821<br />

24082<br />

10109<br />

10109<br />

11987<br />

9907<br />

26647<br />

13132<br />

17517<br />

15598<br />

13405<br />

20305<br />

6494<br />

10115<br />

6494<br />

6494<br />

20993<br />

8641<br />

10990<br />

8641<br />

8964<br />

4859<br />

1521<br />

3209<br />

1521<br />

2089<br />

24082<br />

10060<br />

10060<br />

9695<br />

10206<br />

26647<br />

12514<br />

17696<br />

14551<br />

12758<br />

20305<br />

6473<br />

9196<br />

6473<br />

6473

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