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Date: Sat, 29 Feb 2020 15:45:08 +0100
From: Solar Designer <solar@...nwall.com>
To: john-users@...ts.openwall.com
Subject: Re: PCI express

Hi,

On Sat, Feb 29, 2020 at 09:11:20AM -0500, Powen Cheng wrote:
> Does it matter is a card is on pci express 3.0 x16 or pci express 2.0 x1
> slot?
> 
> Will the higher bandwidth perform better and generate more hash rate?

This depends on hash type and cracking mode.  For slow hashes (and
"non-hashes"), the difference will be small.  For faster hashes, the
difference will be substantial, except that for the fastest hashes when
using on-device mask mode it'll be small again.

In other words, when using JtR, PCIe bandwidth has the most impact on
medium-speed hashes - e.g., on md5crypt.  It is mostly irrelevant for
the slowest hashes (they're similarly slow either way) and for the
fastest hashes (even the fastest PCIe isn't fast enough for them, so
they need on-device mask mode to reach the device's full potential).

Alexander

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