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colesdav
MVP

Zen, Zen+ and Zen 2 cannot support SAM due to the lack of full-rate _pdep_u32? True or false?

Zen, Zen+ and Zen 2 cannot support SAM due to the lack of full-rate _pdep_u32?
True or false?
Anyone know the answer to this? 

See: https://www.anandtech.com/show/16214/amd-zen-3-ryzen-deep-dive-review-5950x-5900x-5800x-and-5700x-te...


 Thanks.

3 Replies
colesdav
MVP

Re: Zen, Zen+ and Zen 2 cannot support SAM due to the lack of full-rate _pdep_u32? True or false?

This article seems to confirm: 

https://www.techpowerup.com/275565/amd-ryzen-3000-and-older-zen-chips-dont-support-sam-due-to-hardwa...

Any confirmation from AMD on this one? 

I am still not sure if it correct or not. 

It would be funny if Intel can implement it for my oldest PCs with Haswell 4790K/4770K CPU. 
Hope it works on 3DMark. 

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goodplay
MVP

Re: Zen, Zen+ and Zen 2 cannot support SAM due to the lack of full-rate _pdep_u32? True or false?

intel sam.PNG

Ryzen 5 5600x, B550 aorus pro ac, Hyper 212 black, 2 x 16gb F4-3600c16dgtzn kit, Aorus gen4 7000s 2tb, Nitro+RX6900XT, RM850, Win.10 Pro..
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colesdav
MVP

Re: Zen, Zen+ and Zen 2 cannot support SAM due to the lack of full-rate _pdep_u32? True or false?

I understand the supposed technical details about it in the initial reports and on the article I just posted. 

There have been a number of  people questioning the accuracy of the above reports in relation to SAM support and performance on older Zen processors. 

I guess we all need to wait until AMD provide an official statement about it.

Last BIOS update for Haswell Z97 Motherboards I run was ~ April 2018 for Intel security fixes so I doubt I will ever see an official BIOS from the manufacturer to enable SAM on Haswell processors. 

However there may be BIOS mods available from enthusiast BIOS modders somewhere to enable it. 
For example BIOS mods were done to enable "above 4G decoding" on some Z87 boards.
It did not involve much modification to the BIOS, was simple to do. It worked.

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