Performance Calculation Guide - Samsung S3C2501X User Manual

DES/3DES

8.5 PERFORMANCE CALCULATION GUIDE

Supposed condition:
— DESINFIFO has already data to be encrypting.
— DESOUTFIFO can be written data to be encrypted.
Cycle Unit (Reference Figure 8-1 DES/3DES Block Diagram)
Unit 1: from DESINFIFO to input buffer (1+1/2 cycle)
Unit 2: from input buffer to DES engine (1 cycle)
Unit 3: DES operation (20 cycles for DES, 60 cycles for 3DES)
Unit 4: from DES engine to output buffer (1/2 cycle)
Unit 5: from output buffer to DESOUTFIFO (2 cycle)
total: 25 cycles for DES, 65 cycles for 3DES
Explain: DES engine consumes fixed cycle per block (25 cycles for DES, and 65 cycles for 3DES). If the DES
operating frequency is 133MHz and the DES has one block to be encrypted, the DES performance is 341 Mbps
for DES or 131 Mbps for 3DES. For more real system condition, the user have to consider how many cycles is
needed for external memory access. The memory access cycle should be included the performance calculation
as follows
DES Performance Calculation Formula
P = (#num of block × 64 bit) / {(time of one period) × [(#num of block × C
— time of one period: 7.5 ns if operating frequency is 133 MHz
— C : 25 for DES, 65 for 3DES
des
— C : the cycle from external memory to DESINFIFO
mem2des
— C : the cycle from DESOUTFIFO to external memory
des2mem
8-10
) + (C + C
des mem2des des2mem
S3C2501X
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