Reusing Old Hardware

Re:Reusing Old Hardware by throwaway1X2 on Thursday October 25, 2018 @10:12PM (#18306235)

The part comparing "Intel Xeon E3 1320 V6" [sic] with older "Intel Xeon E5620" as having the same memory bandwidth, same TDP, more L3 cache, etc., so having "the same performance characteristics" is just plain crazy.

1. Xeon E3 1320 never existed. Was it meant to be 1230?

2. Does DDR4-2400 really have "the same performance characteristics" as DDR3-800 (even after accounting for having 3 channels instead of 2)?

3. How can a 3.5 GHz processor be "the same performance characteristics" as 2.4 GHz one (1.5x more)? Add IPC on top of that.

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Re:Reusing Old Hardware by orev on Thursday October 25, 2018 @11:20PM (#18306509)

3) GHz cannot be used as a speed comparison outside of the same generation of CPUs. A 10 year old 3.5GHz gets nowhere near the same compute power as a modern day 2.4GHz.

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Re:Reusing Old Hardware by benwills on Friday October 26, 2018 @02:27AM (#18307190)

For a lot of basic operations, this is often false.

I have an application I'm working on and tested it across three different generations of CPUS going ~10 years back.

The code was written in C and the fundamental steps were to: mmap() two arrays of structs from a sata 3 SSD, compare the two, and write the intersection to a block of memory. The data size of each array was multiple gigabytes and the operation took more than a full second.

The ~10 year old low powered Xeon L5640 beat the higher-speed ~5 year old Xeon E5-2667 v2, and was only slightly beaten by the 3 year old i7-4790k. In short, they all ran at roughly the same speed.

I would say that this is because of the limits of the SSDs, but then I tested by holding that data in memory rather than disk, then ran the intersection. Same result.

This is a very basic operation that tests the performance of the CPU and memory. And for operations like these (ie: not using SSE2, AVX, etc), the perceived performance difference to the vast majority of people for a secondary home machine may be negligible.

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Re:Reusing Old Hardware by archi42 on Friday October 26, 2018 @05:06AM (#18307740)

That really depends on your load. I once feared a huge performance regression when a test took 2 minutes instead of 40s. Turned out one instance ran on a i7-6xxx machine, and the other on a i7-9x0. Normalizing for the different clock, the newer CPU had a 20% better IPC.

Disclaimer: I don't recall exact numbers, but they should be somewhat close to those given.

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Re:Reusing Old Hardware by bschwindHN on Friday October 26, 2018 @04:16AM (#18307577)

> I would say that this is because of the limits of the SSDs, but then I tested by holding that data in memory rather than disk, then ran the intersection. Same result.

Wouldn't it then just be testing the limits of your memory?

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Re:Reusing Old Hardware by eVeechu7 on Friday October 26, 2018 @01:04AM (#18306900)

I think he means effective performance, ie if the machine is idle 95% of the time with the slow processor and 97% of the time with the fast one it really doesn't matter.

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Re:Reusing Old Hardware by BearOso on Thursday October 25, 2018 @10:19PM (#18306270)

The Xeon E5620 mentioned is also from 2010, 8 years ago, not 11. Of course a Nehalem-Sandy Bridge era processor is still relevant. Many people are still using those today, given the Moore’s law slowdown.

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Re:Reusing Old Hardware by zelon88 on Friday October 26, 2018 @09:25PM (#18313866)

Sorry, I have made this correction.

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Re:Reusing Old Hardware by zelon88 on Friday October 26, 2018 @09:24PM (#18313865)

Sorry. I have made the correction to #1.

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