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Date: Wed, 04 May 2022 16:30:43 +0000
From: Foamy Mai Tai <foamymaitai@...me>
To: john-users@...ts.openwall.com
Subject: Re: More CPU cores vs faster base frequency

Just the advice I was hoping to find - THANK YOU very much, Alexander.

> Out of these, the 20-core is faster for password cracking. However, I'm
> surprised you're looking at Xeon Gold and not something cheaper, or AMD.
> Maybe the refurbished prices you found are good, though.

Admittedly I was overwhelmed in my search and the 20 cores and decent used price caught my eye, and seemed to be more value than what I could get for a higher-end desktop CPU with similar capabilities.

I was also over-prioritizing AVX-512 capability, particularly in light of your revelation that it won't even be put to use for this project! (Again, I tried to do my own homework to figure out how exactly AVX2 & AVX-512 would/would not help me against the scrypt algorithm... but all of the documentation I was finding was either too broad to be useful or too technical for my current knowledge level on the subject.)

Beyond AVX-512, the general trend in the benchmarks seemed to put Intel CPUs at an advantage for this purpose, which is what drove me to them. Perhaps I need to re-look at the recent AMD EPYC lineup.

> Indeed, you also need to consider other
> aspects. For scrypt, that's most importantly number of memory channels
> and memory speeds (primarily bandwidth).

Interesting! So comparing against the Xeon 6148 with 6 channels at 2666 MHz, you’re saying I should get better scrypt performance from, for example, the AMD EPYC 7443P with 8 channels at 3200 MHz? (Slight core # and frequency difference aside.)

Thank you again for the help… I appreciate it.

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