CPU prices starting to fall ( for some processors ) - Page 4

petrw1 · 2017-12-16, 06:13

Quote:

Originally Posted by VictordeHolland

Good choice, I'm very happy with my GTX1080Ti with ASUS STRIX cooler (as you might have read in another thread).

If you want a single PC with bad-ass specs, I would go with a i7-7820X if your budget allows for it (8 cores @3.6-4.3GHz)

Will it be memory channel constrained?

mackerel · 2017-12-16, 08:28

The 7820X is the 8 core big brother to the 7800X (6 core) I suggested earlier. Both support quad channel memory, so if you get some fast ram in there you shouldn't be short. The new L3 cache structure is slower than on consumer level CPUs though, and there are gains from overclocking that.

ET_ · 2017-12-16, 11:02

Quote:

Originally Posted by mackerel

The 7820X is the 8 core big brother to the 7800X (6 core) I suggested earlier. Both support quad channel memory, so if you get some fast ram in there you shouldn't be short. The new L3 cache structure is slower than on consumer level CPUs though, and there are gains from overclocking that.

Does it need an expensive motherboard to unlash its powers?

kladner · 2017-12-16, 15:42

Quote:

Originally Posted by ET_

Does it need an expensive motherboard to unlash its powers?

It needs a 2011-v3 socket board, most commonly, an X99 chipset. Most examples at Newegg which are under $200 US are Open Box or Refurbished.
https://www.newegg.com/Product/Produ...ED&PageSize=36

Prime95 · 2017-12-16, 16:28

I think the Core X series requires a X299 chipset. Motherboards in the low $200s.

Mysticial · 2017-12-16, 17:30

Quote:

Originally Posted by Prime95

I think the Core X series requires a X299 chipset. Motherboards in the low $200s.

If you want to do *any* amount of overclocking, you're gonna need one of the higher-end boards. (~$400 range) None of the entry-level boards have enough VRM cooling to handle the power draw.

I have the Gigabyte Gaming 7 with a 7900X. It's a $400 board with extra VRM cooling. And even that seems to get warm on the VRMs under sustained load (> 250W on CPU).

I have access to some of the bigger chips at work. And all of them easily pull 300W+ with even the slightest overclock.

mackerel · 2017-12-16, 18:05

I'm running a 7800X on the Asus X299 TUF Mark 2, which is one of the cheapest boards around in that area. If you don't care about power efficiency, on custom water, I can run non-AVX at 4.8 to 4.9 GHz, although at the latter it is showing signs of some throttling mechanism I haven't investigated yet. My Prime95 (AVX) power optimised running condition is 4.3 GHz at 1.10v. I haven't done much testing with AVX-512 yet but it either needs more volts or lower clock than AVX. Delidding and liquid metal application only reduced my hottest core by 5C (small FFT load) so that was a bit disappointing.

preda · 2018-05-23, 10:49

Recently I got a new 7820x system. I'd like to share the setup and speed I observe.

Hardware:
CPU i7-7820x (8-core).
MB Asrock Taichi x299
RAM Kinston HyperX Predator 2666 CL13, 4x4GB ( https://www.kingston.com/datasheets/...13PB2K4_16.pdf )

Running a singe PRP task on all the 8 cores, on exponent 80161421, out of the box I was getting (if I remember correctly, need to re-measure) about 3.2ms/it and ~200W total power (measured at the socket).

I overclocked like this:
CPU to 4GHz.
Cache to 3900MHz (from 3400MHz)
RAM to 3200, 1.4V, 16-16-16-43 (from 2666, 1.35V, 13-14-14-39).
Cooler Noctua D15 air.

(Optimizing for CPU architecture: Core i3/i5/i7, L2 cache size: 256 KB, L3 cache size: 11 MB; Resuming Gerbicz error-checking PRP test of M80161421 using FMA3 FFT length 4480K, Pass1=448, Pass2=10K, clm=4, 8 threads)

In this setup I get 2.54 ms/it, 327W at the socket, CPU temperature stable at 70 C.

I must say I'm impressed: Prime95, and the CPU, are extremely fast!

It seems the most further speed increment in my setup is gained by increasing the RAM speed (i.e., mostly memory-bound). The "140W" CPU is using (estimated) ~260W of power, and still has cooling headroom.

Lorenzo · 2018-05-23, 15:07

preda, Could you please make benchmark for 100M exponent (Hardware Benchmark Jest Thread for 100M exponents)?
I really want to buy this CPU. I assume that is the best CPU for all my tasks.

preda · 2018-05-23, 22:31

Quote:

Originally Posted by preda

Cache to 3900MHz (from 3400MHz)

Correction: cache is overclocked to 2900MHz, from 2400MHz.

preda · 2018-05-23, 22:36

Quote:

Originally Posted by Lorenzo

preda, Could you please make benchmark for 100M exponent (Hardware Benchmark Jest Thread for 100M exponents)?
I really want to buy this CPU. I assume that is the best CPU for all my tasks.

Yes I did a quick test, time is 11.96ms/it for PRP test of M332196229 using FMA3 FFT length 18M.

2018-05-23, 10:49	#41
preda "Mihai Preda" Apr 2015 2²×3×11² Posts	Prime95 is freaking fast on i7-7820x Recently I got a new 7820x system. I'd like to share the setup and speed I observe. Hardware: CPU i7-7820x (8-core). MB Asrock Taichi x299 RAM Kinston HyperX Predator 2666 CL13, 4x4GB ( https://www.kingston.com/datasheets/...13PB2K4_16.pdf ) Running a singe PRP task on all the 8 cores, on exponent 80161421, out of the box I was getting (if I remember correctly, need to re-measure) about 3.2ms/it and ~200W total power (measured at the socket). I overclocked like this: CPU to 4GHz. Cache to 3900MHz (from 3400MHz) RAM to 3200, 1.4V, 16-16-16-43 (from 2666, 1.35V, 13-14-14-39). Cooler Noctua D15 air. (Optimizing for CPU architecture: Core i3/i5/i7, L2 cache size: 256 KB, L3 cache size: 11 MB; Resuming Gerbicz error-checking PRP test of M80161421 using FMA3 FFT length 4480K, Pass1=448, Pass2=10K, clm=4, 8 threads) In this setup I get 2.54 ms/it, 327W at the socket, CPU temperature stable at 70 C. I must say I'm impressed: Prime95, and the CPU, are extremely fast! It seems the most further speed increment in my setup is gained by increasing the RAM speed (i.e., mostly memory-bound). The "140W" CPU is using (estimated) ~260W of power, and still has cooling headroom. Last fiddled with by preda on 2018-05-23 at 10:50

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2017-12-16, 08:28	#35
mackerel Feb 2016 UK 700₈ Posts	The 7820X is the 8 core big brother to the 7800X (6 core) I suggested earlier. Both support quad channel memory, so if you get some fast ram in there you shouldn't be short. The new L3 cache structure is slower than on consumer level CPUs though, and there are gains from overclocking that.

2017-12-16, 16:28	#38
Prime95 P90 years forever! Aug 2002 Yeehaw, FL 8279₁₀ Posts	I think the Core X series requires a X299 chipset. Motherboards in the low $200s.

2017-12-16, 18:05	#40
mackerel Feb 2016 UK 2⁶×7 Posts	I'm running a 7800X on the Asus X299 TUF Mark 2, which is one of the cheapest boards around in that area. If you don't care about power efficiency, on custom water, I can run non-AVX at 4.8 to 4.9 GHz, although at the latter it is showing signs of some throttling mechanism I haven't investigated yet. My Prime95 (AVX) power optimised running condition is 4.3 GHz at 1.10v. I haven't done much testing with AVX-512 yet but it either needs more volts or lower clock than AVX. Delidding and liquid metal application only reduced my hottest core by 5C (small FFT load) so that was a bit disappointing.

2018-05-23, 15:07	#42
Lorenzo Aug 2010 Republic of Belarus 262₈ Posts	preda, Could you please make benchmark for 100M exponent (Hardware Benchmark Jest Thread for 100M exponents)? I really want to buy this CPU. I assume that is the best CPU for all my tasks.