
Coffee Lake Review: Initial Numbers on the Core i7-8700K and Core i5-8400 - polskibus
https://www.anandtech.com/show/11859/the-anandtech-coffee-lake-review-8700k-and-8400-initial-numbers
======
LeicaLatte
"The problem here is the same problem we’ve seen with big core parts and
Windows 10, however: these large processors can only take so much before
having to move threads around, to keep both the frequency high and the energy
density low. All it takes is for a minor internal OS blip and the single-
thread power begins to dissipate. Windows 10 famously kicks in a few unwanted
instruction streams when you are not looking, and as a result the average
single thread performance seen on the 8700K might be equal or lower than that
of the previous generation. It becomes an infuriating problem to debug as a
reviewer."

I didn't know this was a big issue with multicore processors, very
interesting. Does this mean that if you OC a single core to the limit to get
the best single threaded performance, you will see drops in performance when
your other cores start getting utilized?

~~~
DigitalJack
I can't quite tell from the current replies if the mechanism of what is going
on is clear. Apologies if this is redundant.

What is happening is a thermal management issue. "turbo" lets you boost
briefly to speeds that _will_ cause the chip to overheat if run long enough.
Their idea to manage this was to play hot potato with which core gets baked.
As soon as it reaches critical temperatures, they turbo up another core and
the OS migrates threads.

So one part of the chip gets hot while the other cools off, and then they
continue back and forth.Personally I'm surprised this doesn't crack silicon or
pop bonds.

With regards to overclocking, I guess I didn't know you could overclock a
single core? Is this pinned or is it adjusting what the "turbo" frequency is?

In anycase, if there is a differential in speeds among cores, the hot potato
thing will probably happen. And if you overclock it will probably happen more.

The only way to combat this would be to either mess with the windows cpu
driver and put your cpu at risk, or make the speed homogenous among all cores.

~~~
JoshTriplett
> "turbo" lets you boost briefly to speeds that will cause the chip to
> overheat if run long enough. Their idea to manage this was to play hot
> potato with which core gets baked. As soon as it reaches critical
> temperatures, they turbo up another core and the OS migrates threads.

This is not an accurate description of how turbo works. You don't have to
migrate away from a core and switch to another.

Turbo simply recognizes that if you have a multi-core processor, and many of
the cores stay asleep and don't contribute to power and thermal demands, then
the remaining cores can take up the slack. The more cores stay asleep, the
faster the remainder can go.

------
jandrese
Another chip, another socket. If you were considering upgrading your CPU in
place you can forget it. You're going to need a new motherboard, with almost
exactly the same set of chips on it but a very slightly different socket.

This socket is probably only going to stick around for this generation too,
the 10nm chips will almost certainly use a new socket.

~~~
lbenes
What is the business advantage for Intel? Swapping out a CPU is trivial, the
whole MB and CPU is a job and time commitment. Are there that few of us
willing to make the upgrade or some major business advantage that outweighs
the upgrade market?

~~~
selectodude
Moving to 6 cores required different power delivery, so they needed a new
socket. It just happens to have the same number of pins as the old CPU. I
would be willing to bet the number of people who want upgrade their CPUs and
currently have a Kaby Lake CPU would number in the tens of thousands.
Engineering around that number of people would be nuts.

------
holtalanm
I took the liberty of comparing the benchmarks online for the i5-8400 vs the
Ryzen 5-1600: [https://goo.gl/R4AQZe](https://goo.gl/R4AQZe)

For single-threaded performance, the i5 wins (no-brainer due to the higher
turbo clock), but for multi-threaded performance, the ryzen is still a winner,
for less money.

Power consumption _is_ higher for the Ryzen though. I'm thinking that the
Ryzen is still the best bet for now as far as bang for your buck, considering
it has hyperthreading AND can be overclocked, and the i5 does not.

Not sure if the i5 can be overclocked. If not, then the Ryzen will probably
beat the i5 in single-threaded performance as well if you OC it.

~~~
mtgx
Disregarding brand loyalty and whatnot, there are very few situations in which
AMD's Ryzen chips aren't a "no-brainer" over Intel's.

Most _rational_ people should be getting AMD's chips and AMD Ryzen-based
devices.

~~~
hyperbovine
I took a hard, rational look at Ryzen for my latest workstation purchase.
Ultimately I went with Intel due to all the reports of crashes under heavy SMT
load on Linux.

~~~
loeg
That's understandable, but it's also worth pointing out that that issue is now
understood and affects only processors manufactured before June 2017. Any
affected processor should be returned for replacement or RMA.

------
jongold
I'm looking at building a PC for deep learning, and I'm just learning about
the importance of PCIe lanes for GPUs. I'm confused by the Coffee Lake numbers
- 16 on the CPU, 24 on the motherboard? Does this mean that you could have 2
GPUs are without slowdown, or does the 'x16 per GPU' advice only take into
consideration the CPU lanes?

reference:
[https://twitter.com/karpathy/status/869289384687714304](https://twitter.com/karpathy/status/869289384687714304)

~~~
dirtyaura
I'm on the same boat as you, building my first deep learning box as we speak.
What I've understood is the following:

if you want to build, or grow your build over time to multi-GPU deep learning
machine, you are better off server-targeted Xeon family processors instead of
this consumer market oriented Core line. Xeon processors typically support
32-40 PCIe lanes, while Core processors support 16. I read that with typical
deep learning loads, utilizing 8 PCIe lanes per GPU is good enough, so with
32-40, you can go up to 4 GPUs.

However, instead of spending tons of money and building a perfect basis for a
hypothetical future DL box from the get-go, I decided to just start with
cheaper parts and go with single GTX 1080 and Core processor. When I hit the
limits of it, I probably know more what I need and likely the technology has
advanced too.

~~~
AlphaSite
Go for an AMD chip, you get 60-128 general purpose Pcie lanes.

~~~
dragontamer
Well, Threadripper AMD anyway.

The key is if PCIe lanes are important, you need to buy a Motherboard that
supports a high number of PCIe lanes. AMD's Threadripper is cheap (for a
workstation) and supports 64+ PCIe Lanes.

Intel's "extreme" line (both chips and motherboard) are the high PCIe count
workhorses, as well as their Xeon chips. But they are much more expensive than
AMD's solution. Even then, an Intel 6950X "only" has 40-PCIe lanes. I wonder
if Intel's new line of "Extreme" will up the PCIe count to better compete vs
AMD.

------
dirtyaura
I find it fascinating how inexpensive CPU processors really are. You pay
approximately same amount of money for top-of-the-consumer-line processor as
you pay for 32GB of RAM or 1TB SSD drive. Modern consumer GPUs are twice as
expensive.

~~~
ktta
Well the problem might be price fixing of RAM (speculation, btw). There's
competition in CPU world but its a different matter in the RAM/HDD world. RAM
has actually been getting more expensive.

[https://www.reddit.com/r/buildapc/comments/6xth78/is_ram_jus...](https://www.reddit.com/r/buildapc/comments/6xth78/is_ram_just_gonna_keep_on_getting_more_expensive/)

------
alkonaut
It says Socket 1151. Can I just drop a Coffee lake CPU into My 1151
motherboard (potentially after a bios upgrade) or will there be caveats such
as chipset model?

~~~
old-gregg
No, the socket is LGA 1151 but the chipset is different: 300-series vs 200.
You need a new motherboard.

~~~
coverband
Why didn't they just use a new socket number for this? Even something like
LGA1151B would have made this clear and easier to search product.

~~~
einrealist
Technically its the same socket. But the voltage is different. Coffee Lake
consumes more.

------
PascLeRasc
What's the usual step when companies brand their product generations with
numbers and they get too big? I can't imagine calling something an "Intel
10400" in two years.

~~~
dagw
286->386->486->Pentium

Pentium->Pentium II->Pentium III -> Pentium IV -> Core

If history is any guide they'll come up with a completely new naming and
numbering scheme soon enough.

~~~
monocasa
I thought Pentium was just because the Trademark office was scoffing at
registering just a string of numbers. So instead of 586, they called it
Pentium.

Core was a total change in design representing a very different lineage than
the current at the time Pentiums, so it makes sense that they'd change the
name.

I'm not sure that I see a similar external pressure in this case.

~~~
jandrese
More to the point, they were running away from the horrible Pentium 4 chips
and wanted people to know that their machines wouldn't run like a dog anymore.

It's kind of hard for Intel to switch up the numbering on a product that is
changed so little between revisions. Plus, having the 10nm chips use the 10
prefix seems like a good coincidence.

------
mark-r
Wake me up when Intel starts offering ECC support in their desktop processors.
Until then Ryzen looks very tempting.

