1. Previously, we discussed about “prototyping” code for SHA1 and SHA256
eval_sha1.sv ( MHz)
eval_sha256.sv (129.4 MHz)
Today, we will consider prototyping the “unfolding” of SHA1 and SHA256 (2 rounds per cycle)
eval_sha1_2x.sv ( MHz, 31% slower Fmax)
eval_sha256_2x.sv (86.99 MHz, 33% slower Fmax)
Note that doing 2 rounds/cycle does not reduce Fmax by 50%, more like 31-33%.

2. eval_sha1
#ALUTS = 205, #registers = 680
Fmax = MHz

3. eval_sha1_2x
#ALUTS = 384, #registers = 679
Fmax = MHz

4. eval_sha256
#ALUTS = 526, #registers = 774
Fmax = MHz

5. eval_sha256_2x
#ALUTS = 940, #registers = 779
Fmax = MHz

6. To implement unfolding, best to read in all words from memory (or generate necessary padding) first before processing each block
To “hide” the delay of reading in 16 words (or generating padding), can read ahead the 16 words (generate padding) for the next block
Unfolding possibly a good design strategy for “DELAY” metric, but you will likely need to do a different design for the “AREA*DELAY” metric.
Can further improve unfolding performance by “pipelining” (see Lecture 10 on unfolding)
Can also pre-compute the W’s and the K’s as they do not depend on A, B, C, D, E …

7. To implement a different unfolding or pipelining strategy for each hash algorithm, you can implement a different state machine sequence. e.g.,