Just like you, I completed my build recently. Before that, for a few years I had used laptops exclusively.

I was blown away by how even a modest desktop [1] is so much faster than even a high end laptop [2]. I believe it's because any laptop will end up throttling because of thermals, unless you get one of those very heavy gaming or workstation laptops with huge cooling systems.

Oh and I had to throw away my laptop because the motherboard failed, all I could salvage was the SSD. Not going to happen with a desktop.

[1] (I have a non-overclockable i5-6500, 16GB DDR4, SSD with SATA3 interface, a GTX 1060 with 6GB VRAM)

[2] My laptop was an i7 quad-core, 16GB DDR4, SSD SATA3, GT840 GPU. Everything except the GPU was better than or equal to my desktop.

The watt budget of a laptop is prohibitive. The watt budget gloves only come off with a desktop.

It's a shame that 2/3rds of Apple's desktop offerings are constrained by that watt budget. iMacs and Mac Minis run on laptop-grade hardware, as I understand.

iMacs run desktop CPUs, but mobile GPUs (which are still pretty fast, but not the fastest).

Apple REALLY needs to come out with a mini-tower Mac supporting desktop graphics cards. And no, I don't mean the new Mac Pro.

Yeah it would be nice to have a headless iMac that you can upgrade that doesn't have server grade components. Right now I'm pessimistic about even the new Mac Pros being upgradable looking at the current iMacs and Macbook Pros.

They could bring back the cube form factor.

I never thought about this. Do laptops perform better when plugged in?

There's a separate line of processors for laptops typically, with Intel it's their U line, which have lower TDP and lower core count by default (i5-XXXXU have 2 cores 4 threads by default, a desktop i5-XXXX will have 4 cores 4 threads).

The prohibitive nature of battery powered devices has pushed Intel's processors to efficient low-powered solutions, but that's a big reason you'll see desktops simply overpowering laptops at the same price range.

Not to say you can never get strong processing in laptops though, they do offer the high-end HQ line which are high TDP mobile processors. Just that the default for Intel mobile processors is "gimped" by design to allow for efficient low-power processing.

Pretty much any laptop with a high-power processor (HQ series) will perform better when plugged in. You can force them to run at higher performance off the battery (go into Power Settings control panel, select "high performance" mode), but they will burn through a battery in like 20 minutes if you're really pushing them.

Sometimes Ultrabook-style laptops will have a higher boost, but they're often thermally limited anyway so running more power just makes them throttle harder.

Some laptops come with a powersupply that isn't good enough to run the CPU on full speed so it will even throttle down when plugged in... (HP I'm looking at you...)

If you have battery power left, it might run faster and drain the battery until it's low and then throttle down. Or just shut down like an older Samsung I saw once.

A lot of laptops, by default, are set to save power significantly more aggressively when running off battery - it's most noticeable when attempting to watch netflix or play games on a cheap laptop.

Yes.

Discovered this recently while working on a GPU-powered ray tracer, plugging my laptop in more than doubled the performance.

Yes but it becomes really noticeable (for me at least) when you get down the the final 5-10% of battery life.

That's probably entirely due to the fresh installation, unless you're doing some very memory intensive stuff and you OCed your DDR4.

I have a 4core/8thread i7 laptop (4630QM) and I cannot get it to throttle after stress testing it for multiple minutes.

The GPU throttles if my thermal paste is getting old and the laptop sits flat on a desk and a game stresses it to 100% all the time. But the CPU I just cannot get to throttle, even with the above conditions being true, unless I remove the paste.

And this is a 13-inch, single fan laptop.

Consider repasting actually, there is no reason your CPU should be throttling.

I can't find much on `4630QM` but a friend of mine bought a laptop from HP that had 4770HQ and it definitely throttled even with the fan at take-off levels.

Hell, especially the (r)macbook pro 15 that I got from my company which had the same 4770HQ - Apple for some reason believes that customers should have their legs burnt and CPU throttled before the fan even spins up.

My bad, had to check the actual laptop order receipt, it's an "Intel Core i7-4710MQ - 2,50 - 3,50GHz 6MB".

Must have it confused with my last laptop's 4/8 i7 product code (which was an i7-3630QM).

The i7-4770HQ is listed as a 2,4 to 3,4 Ghz chip, so there's no reason it should ever throttle in a 15 inch laptop unless the laptop manufacturer messed up real hard (since the same silicon running at a higher frequency, with the same TDP, is adequately cooled by a single tiny fan on a 13 inch laptop).

It's rather unfair to say that laptops generally can't have consumer desktop-level performance on the CPU side, based on a few experiences with specific OEMs.

Now, this changes entirely when 6 and 8 cores are affordable. Desktops make sense again.

depressingly true.

GT840? high-end? laptop high-end is nearly astronomical and still costs premium. I paid 2k for above + 32GB DDR4 + GTX980M.

Oh yes, of course mine was high-end within the category of "business PC laptops", in the grand scheme of things gaming laptops, as you say, are even more expensive but that, if anything, confirms the point I was trying to make.

I've been living the cheap-but-decent portable + big desktop in my personal life for several years now. Between RDP and SSH, I can do practically everything from my laptop with a decent internet connection aside from gaming. Plus, many of those cheap-but-decent laptops get some great battery life, especially if you're offloading the heavy compute onto a different box.

I still drool over getting a sweet $2k+ ultraportable laptop though. I'll let my office buy those things for that work and stick to the cheaper personal life. Portable devices just can't seem to live with the chaos of life, and I'd rather break a $400-500 machine than a $2k machine.

I am doing the same [1], SSH and tmux are my best friends. I did however try the expensive-powerful-laptop first [2], it wasn't worth it and my current desktop beats it in everything but gaming.

[1] $350 DIY PC + a $250 second hand thinkpad

[2] $2200 laptop with the latest i7 and discerete GPU.

I don't have an "ultra portable" but I have a $2500 desktop replacement for work. It's got a 970m and a 6700K. Yes, that's a desktop chip, and it hits 4.2GHz nicely when needed.

I mostly just tote it to the office and home, so it's quite nice.

Look at synthetic benchmarks of your chip and the MBP. It's night and day difference. I won't use a laptop to develop on either. It's too slow. (And the ergonomics are terrible anyways so a monitor, keyboard, mouse, etc are all necessary anyways)

I couldn't agree with you more, I believe these days a developer can gain more with a Chromebook for portability, and a powerful desktop/cloud VM for the beefy tasks. You could end up paying the same (or even less) as a high end laptop, but you could gain more power and benefits this way.

> On paper, my MacBook Pro with 16Gb RAM and 3GHz i7 shouldn't be that much worse than my desktop with 32Gb RAM (most of which is unused) and 3.6GHz i7.

It is much worse. Remember that the laptop i7 is a much lower power part.

My i7 2600k is getting a bit long in the tooth, but I can get it to sweat by compiling yocto poky. Especially building Webkit/Chromium and Qt eats memory and cores like nothing.

As a side note, I saw someone on facebook sniping a dell m905 blade in some NY depot for less than a 100$ the thing came with 4 AMD cpus and loads of ram (maybe 64GB).

It's neither recent or pristine, but having a slim 4C/64GB thing at that price is worth considering.. no more rpi clusters :p

> dell m905 ... 100$

These are really old, Socket F, DDR2 blades. Given that the corresponding blade center will be needed as well, probably not that good a deal.

Alright, and what about more recent blades around 500$ ?

I considered blades but at least for me I concluded they were a bad fit:

- The centers are large and heavy, needs a fair amount of space, can't really be handled alone. Also means they're shipped on a pallet, which is somewhat expensive.

- Blades are less common overall compared to servers

- Blades have more peculiar I/O than normal servers, you can't just stick an IB card or GPU in there

- The backend I/O modules are fairly rare 2nd hand, so either you find a center which has the modules you want or you're SOL

I have both HP g6 blades and Dell C6100 blades at home...you can get both for about $200/node with 2xquad core and 24G of Ram. The only real issues with them are the NOISE and the electric usage. 16 nodes sounds like your living in an airport. The HP is 8 nodes with a shipping weight of 300 pounds. Cost $350 for shipping, IIRC - pop the sleds and the heaviest part is probably ~25 pounds, easy to handle without help. The HP blades also came with mellonox 10G cards.

How difficult would be to add liquid cooling ?

With a drill and duct tape, it can be done

and a drop of anti freeze

Fair points

Per https://news.ycombinator.com/item?id=13607257 ~3 months ago:

I'd start with a used Dell Precision T7xxx series off of Ebay for a <$300 including RAM and a Xeon or two

T7500 are above 500$ with 24GB of RAM, T7600 are quickly above 1000$. Not expensive but not a sub 100$ pizza box.

Thanks for the tip though, could be of use for a friend.

T7500 with 48GB RAM is $300 + shipping on ebay: http://www.ebay.com/itm/Dell-T7500-Home-PC-Xeon-6-Core-3-06G...

As a side note to your side node, rpi clusters are a terrible idea in any case :-)

My impression is that Moore's law is totally dead and CPUs have not changed in any meaningful way in 4 years. My old i7-4771 feels just as fast as my new i7-6950x. The 10 cores are nice when you need 10 cores though.

Moore's law doesn't concern it self with clock speed, but with the number of transistors. While the clock speed have stayed about the same, the number of cores have increased. The problem is that it's really hard to make a program that takes advantage of all those cores, so you as a regular consumer doesn't see any difference in your day to day usage.

One thing I find myself asking a lot is if it's really hard to make a program take advantage of the cores or if the prevalent tooling and paradigms of today make it hard to take advantage of the cores.

While most programs are not embarassingly parallel in nature, I suspect the latter plays a bigger role than most of us tend to admit.

I think you are exactly right. I've done a lot with concurrency, and the fact is that there is no life vest so you better know how to swim. I think an architecture made specifically for programs to take advantage of concurrency would help an enormous amount.

Right now we are two steps removed. There aren't even many good data structure implementations out there. There is moodycamel::concurrent_queue and different memory allocators like jemalloc and the new rpmalloc, but the vast majority of programmers likely don't even realize that malloc locks and kills concurrency. Maybe they grab something from boost that just surrounds a data structure with a mutex, which is lazy bullshit.

I actually think the majority of software that runs slow can be made to be sped up nearly linearly using dozens of threads, but the few niche libraries that help are overly complicated to compile and use, bloated with enormous dependencies and end up being a minefield of usage. At the moment many people's idea of multi-threaded is mostly fork-join techniques like openMP and that will never scale to using all cores throughout the whole program, since is one very narrow technique.

The particular implementation I had in mind is Erlang. Due to the green thread implementation, immutable data, and message passing, Erlang is able to offer a simple, robust concurrency platform. Of course it's still possible to write very sequential code but generally someone writing idiomatic Erlang won't have to go out of their way to get concurrency.

It is also far from ideal when it comes to performance from what I've seen. Maybe its overall design is good, but I don't believe that adding so much overhead over native programs is necessary.

From my somewhat limited reading it seems that the only inherent performance hit in Erlang's implementation is that all its processes can be interrupted externally, I think the term is cooperative multitasking?

Otherwise I think the rest of Erlang's performance is because it's optimized for reliability and distribution rather than raw performance.

I really think there's only two rays of hope for parallel programming.

One is promises (async/await). This takes the burden off the programmer for explicitly managing concurrency, and potentially allows lazy evaluation in many cases (if non-side-effecting). I've never worked in Lisps but it seems like a viable model in many ways.

The one I wanted to bring up was probabilistic programming. Imagine a tree where there's not just one place to put something, there's many, possibly distributed. As such you greatly reduce the chances of contention from multiple threads. They would also probably (almost necessarily) reduce the amount of rebalancing work.

GPUs seem like the perfect model here in multiple ways, not only do you have the massive degree of threading that surfaces any problems in such things but you also have the degree of threading to deterministically search these kind of structures. GPUs also highly discourage things like CAS or mutexing that we need to move away from.

(PS nice username)

I'm not sure how the tree you are describing helps anything. Reading can always be done concurrently, it isn't the problem - all threads can read from the same memory at the same time. The problem is writes, which means any alterations.

GPUs are useful for the kinds of parallelism that has always been known to be easy - fork join with all threads writing to new memory. There is no mystery to how to do this.

> CAS or mutexing that we need to move away from

compare and swap is the backbone of lock free programming. Mutexes to me seem to rarely be ideal, but there is no getting away from compare and swap as far as I know.

As someone with only a basic understanding of threads, what is a better idea than fork/joins for scaling? Are you talking about thread pools or something else?

Yes for thread pools instead of forking (could be process pools too). But that's only scratching the surface. It's how you communicate with those threads and allocate their work that makes the difference.

I think the quick and dirty answer is yes, although I doubt I would structure things the same way as a normal thread pool.

If you think about the heart of the problem, it is really synchronization, and that only needs to happen in certain places in programs. Anything you can break up into pieces that can be transformed independently can be leveraged for concurrency, which also implies that independent stages in a pipeline can be concurrent as well.

My 3370 i7 still is 'good enough' like, 4 years later. I'm itching to upgrade the CPU/RAM/Mobo but I can't really justify it.

The nice thing is, I can throw a new GTX and a PCIe SSD in and that'll have quite a bit of benefit. Custom PCs are awesome!

I have an FX 8350, and I really want to upgrade. Performance per core of the newest processors are approaching 2x of mine. Trouble is, except for Civilization, no game actually needs a faster processor. It's really hard to justify. Processors just last a really long time these days.

Cities: Skylines with large cities benefits very much of a higher core count, as the citizen/vehicle simulation parallelizes nicely. No experience how well it behaves with Ryzen though, but at least it is utilizing all cores on my trusty old Sandy Bridge i7.

The 8350 has no shortage of cores, at least as long as there's little floating point calculus going in.

I dunno, I just spent a couple thousand on a Dwarf Fortress machine. It's still single threaded :(

It is true that moore's law no longer applies to CPU's, but it is not as if no advances are made at all, provided you pick the right CPU.

The single thread performance on the 6950X is pretty low, and in fact pretty much on par with that 4771. If you want higher single-thread performance you have to opt for fewer cores at a higher clock rate, something like the i7 7700K, which would definitely perform significantly better than the 4771. The 6950X really only makes sense if you have a workload that needs those 10 cores.

See https://www.cpubenchmark.net/singleThread.html for the comparison.

The HEDT chips have very low stock clocks but they overclock really well.

Broadwell is kind of an exception here since it clocks so poorly both in the small-chip and HEDT form. But for example, 4.7 GHz is a good OC for Small Haswell and the Haswell-E HEDT chips will usually go to at least 4.5 GHz.

(of course the major caveat here is power - a highly OC'd 8-10 core chip can easily pull 200-250 watts package TDP on a normal workload, 300+ watts as measured at the wall. For an AVX-heavy workload like Prime95, add another 100 watts package TDP.)

So overall the penalty for using HEDT chips is nowhere near as big as you are implying here. It's something on the order of 4% loss of single-thread performance to go from 4-core to 8-10 cores. It just doesn't come that way out of the box - largely because anyone who buys a 10-core gaming chip for $1700 knows exactly how to do all this.

The bigger problem is that the HEDT chips are 2 generations behind the smaller chips. Broadwell vs Broadwell-E, the numbers look fine, but Kabylake has some IPC improvements and clocks significantly higher than Broadwell does.

This is one of those things that actually can be blamed on "Intel being lazy because they have no real competition". They could certainly push the HEDT chips out a little faster instead of waiting to work out all the bugs in the smaller chips, it would just be a bit riskier for them.

The Moore's law is maybe not dead, but it indeed feels that the speed isn't changing that much.

Think about that: a 4 back your PC started in 10 seconds and 2 years back it's starting in 5 seconds, that's 5 second difference that you feel.

Currently the PC's start at 2.5 seconds and the speed difference is much less, so it feels like the power is not progressing that fast.

I have recently "upgraded" my desktop with an SSD (but have an old CPU i7 4780k or something) and it loads in a few seconds. But I don't want to upgrade my CPU just yet as it will only make everything only 1 second faster, not worth 300 USD I think.

But if you do a lot of data processing, software builds, ... You can increase the speed much more, and then it should matter.

I just replaced my nearly 6 year old Core i5 laptop with a newer Core i5 laptop. CPU performance was fine on the old one, and while the new one probably score better on benchmarks, it's not noticeably faster than some previous jumps(such as the old Core i5 laptop replacing a 3 or 4 year old Core 2 Duo laptop). Of course there were still reasons to upgrade with the biggest being far better battery life and of course non-CPU upgrades in the new laptop like a much better screen and an SSD(which I probably would have upgraded the old one with and kept it if not for the screen and battery life).

I'll toss a comment in from a layman: Isn't it also true that cores are adding more and more specific instruction sets to boost common workloads? Graphics, encryption, etc.

Then you have improved architectures, memory/cache access, inter-core communications... there are more ways to improve a chip.

I agree with your snetiment, for general workloads. I have a 4 year old Haswell and it's working like I imagine the i5s today would perform on a basket of workloads.

Are you, primarily, a developer? Did you find enough scenarios where i7-6950X feels justified, aside from rendering, encoding where this CPU really shines? What does the rest of the setup look like?

Thanks!

Moore's law is not about serial processing speed, it is about transistor density.

The two went hand in hand for so long, it's hard not to feel the loss. Smaller transistors were able to be clocked faster - until they couldn't. For a while they were able to use higher transistor counts to get more instructions per clock, but even that strategy is running out of steam. The big news about Ryzen is that it was finally able to catch up to Intel in that regard.

Just because people want it to be about serial processing speed doesn't mean that it is. The reason it is inaccurate to say that moore's law has ended is that there are still transistor density increases, albeit more slowly. These don't lead to the same clock speed increases or serial processing speed increases, but they do lead to more cores in both CPUs and GPUs.

Equating the single core speed of Intel's latest CPUs and moore's law is just another case of simple, easy and wrong.

> For a while they were able to use higher transistor counts to get more instructions per clock, but even that strategy is running out of steam

On a single core, not over a whole processor, as can be seen by the fact that there are 22 and even 72 core processors available now.

> The big news about Ryzen is that it was finally able to catch up to Intel in that regard.

This has nothing to do with Moore's law, it is a result of processor architecture.

The first 30 years of Moore's law showed a direct correlation between transistor density and clock speeds. Yes it's not Moore's fault that this correlation broke down, but we can still mourn its passing.

> On a single core, not over a whole processor, as can be seen by the fact that there are 22 and even 72 core processors available now.

A worthwhile development, but not a panacea. I'd suggest you become familiar with Amdahl's law: https://en.wikipedia.org/wiki/Amdahl%27s_law. There's also some give-and-take between core count and individual core performance.

> This has nothing to do with Moore's law, it is a result of processor architecture.

But Moore's law is an enabler of more sophisticated processor architecture.

> but we can still mourn its passing

Once again, there are still transistor density improvements.

> A worthwhile development, but not a panacea. I'd suggest you become familiar with Amdahl's law

I'm not sure what you are trying to say here. Are you going back to saying computers aren't getting faster and then trying to say that moore's law is therefore dead when we've already established that it was never about speed?

Also what is your point about Amdahl's law? I work with lock free concurrency all day every day and if you are trying to say that more cores doesn't mean more speed because of Amdahl's law, that is pretty shaky ground to say the least. For some reason people seem to assume that if the software they use isn't using multiple threads effectively that it must be impossible. This is FAR from the case. Most programmers don't know how to work with concurrency and most software is trapped in legacy architectures that make parallel computations become painful changes.

> But Moore's law is an enabler of more sophisticated processor architecture.

Again, this tangential and not even really true. AMD's CPU architectures suffered while their GPUs performance and manufacturing process has remained competitive.