Re: Fwd: Intel and 512b registers, IBM and more registers

[Ian McIntosh <ianm@xxxxxxxxxx>]

With 16 vector registers of 512 bits (64 bytes) each, the Intel Xeon has 8192 bits (1024 bytes) of vector registers.

With 64 vector registers of 128 bits (16 bytes) each, the IBM POWER7 and the new POWER8 also have 8192 bits (1024 bytes) of vector registers.

Having enough bits doesn't make it easy to use them for complete arithmetic.  Before an instruction starts down the pipeline the hardware needs to know which registers it will read and which register it will write.  For efficient complete arithmetic that information is hard to provide.  Also the throughput would be limited because you don't know until an instruction completes whether it resulted in a carry implying the next higher register group needs to be handled, so it would be one instruction at a time.  Still, having enough bits is better than not having them, being one less impediment.

- Ian McIntosh          IBM Canada Lab         Compiler Back End Support and Development


"Corliss, George" ---2014-05-01 06:33:49 AM---P1788, A friend of P1788 writes:

From:	"Corliss, George" <george.corliss@xxxxxxxxxxxxx>
To:	Ian McIntosh/Toronto/IBM@IBMCA,
Date:	2014-05-01 06:33 AM
Subject:	Fwd: Intel and 512b registers

---

P1788,

A friend of P1788 writes:

Try a google search on "intel-xeon-phi-coprocessor-codename-knights-corner", and look at:

https://software.intel.com/en-us/articles/quick-start-guide-for-the-intel-xeon-phi-coprocessor-developer

In particular, this describes the 512b registers:

https://prd1idz.cps.intel.com/sites/default/files/article/330164/an-overview-of-programming-for-intel-xeon-processors-and-intel-xeon-phi-coprocessors_1.pdf

If you like, please share this with the 1788 group - but without attributing the links to me.

George Corliss[attachment "signature.asc" deleted by Ian McIntosh/Toronto/IBM]