 |
|
|
|
|
|
| |
| |
|
|
|
|
| |
| |
|
|
Am 24.08.2018 um 15:51 schrieb William F Pokorny:
> Interesting - especially it not slowing over time. Supposing:
Why should they?
Modern CPU cooling systems dissipate heat very quickly. If POV-Ray were
to max out the cooling system's capacity, it would show within a couple
of seconds.
> Mike posted a wikipedia link for the i5 generations and something which
> caught my eye there is the turbo boost is being applied to your
> processor relatively evenly across all cores. 10/10/11/11/11/12
> multipliers of 100mhz where on older processors it was more unevenly
> boosted and by less. Expect this playing a part in your good performance
> too.
>
> I wonder if having the hyperthreading circuitry off in each core - my
> understanding is it is there, but disabled - allows each core to run
> cooler? There would be less demand for on die core specific storage too
> I guess with just one thread.
Probably. There's more chip area than if the HT circuitry were
completely absent, so there's more area to dissipate the heat. Also, the
components that would normally be shared between HT units won't be maxed
out and thus create less heat. So given the same cooling system, with HT
off the CPU will indeed inevitably run cooler. But the CPU may be
specified at a lower TDP, in which case a weaker cooling system may be
employed and thus resulting in the same CPU temperature.
I'm not sure whether Intel does indeed produce cores with HT circuitry
existing yet disabled, but producing non-HT CPUs in this manner does
make sense: You can just produce HT CPUs, and if during die testing you
find that a CPU has defective "semi-cores" you can just blow a fuse to
disable HT and sell it as a lower-tier CPU.
Intel has employed this strategy at least as early as the 80486 days,
when they sold dies with functional FPUs as 80486-DX, and those with
faulty FPUs got a fuse blown and sold as FPU-less 80486-SX. And the
external 80487 FPUs you could buy to upgrade such systems were actually
fully-fledged 80486-DX dies that would just take over the entire system,
disabling the 80486-SX installed in the mainboard's CPU socket.
> My memory not quite right on things with respect to the current
> generation of i5s, but the more cores no threads direction at similar
> price is good news for POV-Ray.
Please don't call it "no threads". Threads are a software thing, a means
of utilizing multiple cores by a single application without too much
overhead. The hardware thing is "hyperthreading", a means of multiple
execution units sharing certain functional blocks in the CPU to utilize
them more efficiently.
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
On 8/24/2018 9:51 AM, William F Pokorny wrote:
Interesting. I would have expected the bottom CPU to perform better due
to more threads and higher clock speed.
Mike
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
Le 24/08/2018 à 20:51, Mike Horvath a écrit :
> On 8/24/2018 9:51 AM, William F Pokorny wrote:
>> james 1275 32.93 # i5-8400 @ 2.8GHz (6 cores 6 threads)
>> cyd 789 20.38 # i7-4770 @ 3.4Ghz (4 cores, 8 threads)
>
> Interesting. I would have expected the bottom CPU to perform better due
> to more threads and higher clock speed.
>
>
> Mike
But nobody looks at the speed of the memory (from tomhardware website):
* i5-8400 uses ddr4 2666
* i7-4770 uses ddr3 1600
DDR4 2666 has a bandwidth of 21333 MB/s
DDR3 1600 has a bandwidth of 12.8 GB/s
12.8 vs 21.3 !
That's the advantage of the new generation.
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
Am 24.08.2018 um 20:51 schrieb Mike Horvath:
> On 8/24/2018 9:51 AM, William F Pokorny wrote:
>
> Interesting. I would have expected the bottom CPU to perform better due
> to more threads and higher clock speed.
i7-4770 has a max clock of 3.9 GHz,
Despite being rated at 2.8 GHz, the i5-8400 can actually go up to 4.0
GHz, given adequate cooling. The i7-4770 can only go as high as 3.9 GHz.
The i5-8400 also has more cores, which is more important than the number
of concurrent threads. Each thread beyond the number of cores only
translates to about 20% to 25% a core's worth of added computing power,
but only about 1/5 to 1/4 a core's worth, so the i7-4770 is effectively
worth about 5 threads.
In addition, the i5-8400 is four generations newer than the i7-4770,
which presumably translates to some additional performance improvements
here and there from miscellaneous optimizations.
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
Am 24.08.2018 um 21:39 schrieb Le_Forgeron:
> Le 24/08/2018 à 20:51, Mike Horvath a écrit :
>> On 8/24/2018 9:51 AM, William F Pokorny wrote:
>>> james 1275 32.93 # i5-8400 @ 2.8GHz (6 cores 6 threads)
>>> cyd 789 20.38 # i7-4770 @ 3.4Ghz (4 cores, 8 threads)
>>
>> Interesting. I would have expected the bottom CPU to perform better due
>> to more threads and higher clock speed.
>>
>>
>> Mike
>
> But nobody looks at the speed of the memory (from tomhardware website):
> * i5-8400 uses ddr4 2666
> * i7-4770 uses ddr3 1600
>
> DDR4 2666 has a bandwidth of 21333 MB/s
> DDR3 1600 has a bandwidth of 12.8 GB/s
>
> 12.8 vs 21.3 !
>
> That's the advantage of the new generation.
I'm not sure that translates to much of a performance gain in POV-Ray.
The memory bandwidth limits the peak throughput under sequential read
access.
Most of POV-Ray's memory accesses are probably random access though, and
there memory latency is the limiting factor, not bandwidth.
In terms of latency, DRAM hasn't seen any noticeable improvement for ages.
Also, RAM access doesn't seem to be a bottleneck for POV-Ray anyway:
There are few applications (even computation-heavy ones) that drive CPU
temperatures quite as high as POV-Ray, indicating that the CPU spends a
lot of time doing actual work rather than waiting for data to be fetched
from memory. Presumably POV-Ray's most heavily accessed data typically
fits well within the L3 cache.
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
dick balaska <dic### [at] buckosoft com> wrote:
> Any overclocking I do is provided by official intel. I.e. the new i5
> overclocks itself. "turbo mode"
By "turbo mode," do you mean turbo boost? That is not the same as overclocking.
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
On 08/24/2018 01:58 PM, clipka wrote:
> Am 24.08.2018 um 15:51 schrieb William F Pokorny:
>
>> Interesting - especially it not slowing over time. Supposing:
>
> Why should they?
>
> Modern CPU cooling systems dissipate heat very quickly. If POV-Ray were
> to max out the cooling system's capacity, it would show within a couple
> of seconds.
>
I've not seen that behavior for an extended render on a machine with
turbo boost active is the short answer.
My old i7-920 - before I over-clocked it with the turbo mode turned off
- didn't hold the turbo boost frequency for long. I was doing long
single image isosurface stuff at the time. Dick appears to be getting a
3.8GHz 'core' over time and under load.
A reason I suggested the grep command is I wonder if all the cores are
maxed out with respect to the multipliers. Are some cores in fact being
throttled? The 3.8ghz number is a core seeing a 10x 100Mhz but you can
get up to 12x 100MHz on a core. I don't know if thermal throttling is by
core or by die.
I further wonder how constant the reported 3.8GHz number really is. On
my i3 the frequency values reported in /proc/cpuinfo look to be
relatively instantaneous. I'm not under load and those MHz values change
dramatically every time I look. I think we'd need to monitor the
performance over time for a full image render to be sure the 3.8GHz held.
Dick is rendering frames. Maybe there is in fact some periodicity in the
actual performance where a frame starts with turbo boost maxed out and
then it tails off. Maybe thermal stuff isn't an issue because he is
rendering frames and there is a cool off period between frames.
I worked for a long time on the hardware design side of CPUs and cache
chips and power consumption/heat generation grows exponentially with
frequency increases. Your right, if limits kick in, it happens fast. My
thinking is 2.8GHz is the performance Intel can guarantee under all
loads given the manufacturing process variation and shipped cooling at
some expected "end of life." Otherwise, they'd be claiming a better base
performance & charging for it, or, somehow handicapping the CPUs aimed
at lower end boxes so as not to eat into their higher end - higher
profit - business.
Though, AMD is again a serious player, maybe they are somewhat being
forced to eat the high end business and what we see with Dick's new i5
is a result.
All just me pondering. I don't know anything for sure - even that. :-)
>
> Probably. There's more chip area than if the HT circuitry were
> completely absent, so there's more area to dissipate the heat. Also, the
> components that would normally be shared between HT units won't be maxed
> out and thus create less heat. So given the same cooling system, with HT
> off the CPU will indeed inevitably run cooler. But the CPU may be
> specified at a lower TDP, in which case a weaker cooling system may be
> employed and thus resulting in the same CPU temperature.
>
> I'm not sure whether Intel does indeed produce cores with HT circuitry
> existing yet disabled, but producing non-HT CPUs in this manner does
> make sense: You can just produce HT CPUs, and if during die testing you
> find that a CPU has defective "semi-cores" you can just blow a fuse to
> disable HT and sell it as a lower-tier CPU.
>
> Intel has employed this strategy at least as early as the 80486 days,
> when they sold dies with functional FPUs as 80486-DX, and those with
> faulty FPUs got a fuse blown and sold as FPU-less 80486-SX. And the
> external 80487 FPUs you could buy to upgrade such systems were actually
> fully-fledged 80486-DX dies that would just take over the entire system,
> disabling the 80486-SX installed in the mainboard's CPU socket.
>
Agree & that last bit about the 80487's being in fact 80486-DX dies I
did not know.
>
>> My memory not quite right on things with respect to the current
>> generation of i5s, but the more cores no threads direction at similar
>> price is good news for POV-Ray.
>
> Please don't call it "no threads". Threads are a software thing, a means
> of utilizing multiple cores by a single application without too much
> overhead. The hardware thing is "hyperthreading", a means of multiple
> execution units sharing certain functional blocks in the CPU to utilize
> them more efficiently.
>
Good point. I got sloppy with the wording.
Bill P.
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
Am 25.08.2018 um 18:10 schrieb William F Pokorny:
> A reason I suggested the grep command is I wonder if all the cores are
> maxed out with respect to the multipliers. Are some cores in fact being
> throttled? The 3.8ghz number is a core seeing a 10x 100Mhz but you can
> get up to 12x 100MHz on a core. I don't know if thermal throttling is by
> core or by die.
Where do you get those numbers from?
From all I know (and what a quick random peek at the internet
confirmed), CPU speed is per core, not per package.
> I further wonder how constant the reported 3.8GHz number really is. On
> my i3 the frequency values reported in /proc/cpuinfo look to be
> relatively instantaneous. I'm not under load and those MHz values change
> dramatically every time I look. I think we'd need to monitor the
> performance over time for a full image render to be sure the 3.8GHz held.
What you might be seeing is the CPU not throttling due to overheating,
but due to being bored.
Also, if this is a per-CPU speed, it may be averaging over all cores,
even cores shut down entirely due to being bored.
> My thinking is 2.8GHz is the performance Intel can guarantee under all
> loads given the manufacturing process variation and shipped cooling at
> some expected "end of life." Otherwise, they'd be claiming a better base
> performance & charging for it, or, somehow handicapping the CPUs aimed
> at lower end boxes so as not to eat into their higher end - higher
> profit - business.
Certainly. At the miniscule dimensions they're currently working at, I'd
be surprised if their tests could catch all the bad apples; so it's
reasonable to assume that they're working with safety margins, and
rating the CPUs for the worst case scenario.
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
On 08/25/2018 01:26 PM, clipka wrote:
> Am 25.08.2018 um 18:10 schrieb William F Pokorny:
>
...
>
> Where do you get those numbers from?
They came off the Wikipedia page Mike posted in this thread.
>
> From all I know (and what a quick random peek at the internet
> confirmed), CPU speed is per core, not per package.
>
>
...
>
> What you might be seeing is the CPU not throttling due to overheating,
> but due to being bored.
>
> Also, if this is a per-CPU speed, it may be averaging over all cores,
> even cores shut down entirely due to being bored.
>
I wasn't trying to suggest overheating on my machine. My machine is not
under load - just thunderbird and some xterm windows up. The point I was
trying to make is how quickly the frequency numbers in /proc/cpuinfo
change. Suppose Dick's machine starts a new frame. At the very beginning
things are cool. The CPU (I suspect rather each core as you suggest)
detects it has meaningful stuff to do so turbo boost it is. Initially no
reason not to max turbo boost out; things are cool. Suppose it's in
those first few seconds Dick grabs the frequency values from
/proc/cpuinfo. They're going to be maxed out. Maybe those maxed out
turbo frequencies hold for the entire frame, maybe not. We don't really
know unless we sample at a fairly high rate over time.
Otherwise, I agree my machine is part of the time idling at a lower
frequency and very likely operating voltage too. I see quite large
differences between the 4 hyper-threads over time with a bottom at
800MHz and a top end of 3400MHz, but I've got no idea how the detailed
accounting works. I expected the hyper-threads to hang together in pairs
with respect to frequency as there are two per core, but it's not
reported that way.
>
...
>
A couple thoughts I had this afternoon along the lines of your thinking
there is plenty of cooling to hold the max turbo frequencies. Supposing
the i5s are aimed mostly at laptops; the cooling in a box enclosure is
much better. Second, my i7 920 experience with turbo boost is 10 years
dated.
Bill P.
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
On 08/23/2018 06:15 AM, dick balaska wrote:
> $ cat /proc/cpuinfo
> model name : Intel(R) Core(TM) i5-8400 CPU @ 2.80GHz
> siblings : 6
> cpu cores : 6
I'll bet the argument on linux-kernel was fun.
"Dude, it's 5 siblings!"
Linus: "Bite me. I say 6."
(Linus is a potty mouth)
--
dik
Rendered 1024 of 921600 pixels (0%)
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
|
|
