LTspice needs high power laptop - Page 1
Forum section: electronics / general

author: ocset
author_rank: Super Contributor
timestamp: May 25, 2018, 09:00:58 pm
content: Hello,We've just purchased a new laptop, a "Lenovo Yoga 510".It comes with a 20V, 45W Power adapter.The docs that came with the laptopconfirms that this is right.We believe that LTspice needs at least a 120W laptop power supply, because LTspicemakes the computer's processors use a lot of energy.Do you agree?

author: The Soulman
author_rank: Super Contributor
timestamp: May 25, 2018, 09:27:44 pm
content: It kinda (completely) depends on the maximum power draw of the laptop if lenovo says a 45W brick is adequate for your modelthen it is save to assume it is...Yes heavy cpu loads will make the power consumption go up, but never above max rated.

author: Kleinstein
author_rank: Super Contributor
timestamp: May 26, 2018, 07:49:17 am
content: A 40 W power rating is a rather low value for a computer, but I would expect it to be sufficient for the computer it came with. If the computer can live with that amount of power, a higher power supply would not help. Those small laptops can't get rid of much more power, so they have to be rather energy efficient. Worst case the short time LTspice usually needs for a simulation the battery can deliver additional power - though I doubt this is needed. Usually the power supply is slightly more powerful than the laptop maximum demand so one can still charge at a reasonable speed during normal use.Unless one does really demanding simulations (e.g. long runs with something like switched mode converters to get a transfer-function for the loop) the computational demands are not that high compared to modern PCs - this was different in the early times of spice, when mainframes were less powerful than a modern smartphone. On my laptop, LTspice usually does not make the CPU Fan to run any faster. A slower computer can still run Spice - it just takes longer.

author: BravoV
author_rank: Super Contributor
timestamp: May 26, 2018, 07:55:12 am
content: If you're serious using LTSpice, especially on heavy simulation, use desktop with multiple cores.Laptop especially that Yoga 510 is not considered high performance machine, not in that price range, as I own Yoga 520.Also delete/uninstall all the crap applications and don't run multiple programs when doing simulation.A 16GB RAM and SSD/NVME will improve alot.

author: AndyC_772
author_rank: Super Contributor
timestamp: May 26, 2018, 10:04:25 am
content: Quote from: treez on May 25, 2018, 09:00:58 pmWho is "we"?How exactly have you quantified "a lot"?If you think there might be a problem with the specification of the power adapter, measure the voltage and current accurately on both the input and the output, when the laptop is running a simulation. Determine the input and output power. Check to see if the output voltage reduces significantly, or if there are any other signs that it's overloaded.Correct me if I'm wrong, but don't you design mains powered equipment for a living...?

author: ocset
author_rank: Super Contributor
timestamp: May 26, 2018, 11:30:47 am
content: I must admit im surprised similar spec'd laptops just a few years apart have such different power demands. Easynote from a few years ago comes with a 120w smps, but lenovo with just a 45w one.

author: chris_leyson
author_rank: Super Contributor
timestamp: May 26, 2018, 11:51:13 am
content: Been running LTSpice on a Windows 10 tablet without any problems, Intel Atom Z3735F 1.33GHz processor, probably draws 5W to 6W. To say LTSpice needs 120W power supply is BS. If you used a bit of commom sense you could open up task manager and look under the processes and performance tabs to see what is running and how much resource is being used. All this post shows is lack of common sense when trying to diagnose an issue.

author: Marco
author_rank: Super Contributor
timestamp: May 26, 2018, 11:51:37 am
content: It's a thin 14" convertible, they couldn't run at high power if they wanted to ... unless you want it to start hovering when the fans really get going. I question the sanity of desktop replacement laptops in the first place, but this isn't one.That said, unless you run multiple simulations with a range of values components/temperature/whatever it's not like LTSpice really hits the CPU hard. It essentially uses a single core even when using multithreading for a single simulation.

author: Ice-Tea
author_rank: Super Contributor
timestamp: May 26, 2018, 12:23:44 pm
content: Totally.You should write a complaint to those Intel guys. They clearly don't have a clue.

author: wraper
author_rank: Unknown
timestamp: May 26, 2018, 12:27:26 pm
content: I wonder how many more nonsense threads this guy will start.QuoteAnd I believe all of you must be fired and kept away from electronics for safety of society.

author: wraper
author_rank: Unknown
timestamp: May 26, 2018, 12:34:03 pm
content: Quote from: treez on May 26, 2018, 11:30:47 amIt's CPU has 15W TDP

author: ocset
author_rank: Super Contributor
timestamp: May 26, 2018, 02:49:07 pm
content: I gratefully confess to being completely stupid. The only way i would know how much power was drawn from the offline SMPS whilst ltspice was running would be to chop its output lead, strip a wire back, ...solder in a sense resistor, and then read the voltage across it....but omitted to act thus, as i dont have any sidecutters, solder, resistors etc with me at the moment...mine are all at the workplace. as they dont buy them for us

author: AndyC_772
author_rank: Super Contributor
timestamp: May 26, 2018, 05:53:12 pm
content: Just make up a short extension lead with the right plug and socket, and insert a multimeter in series. You don't need to damage anything just to measure the current.

author: wraper
author_rank: Unknown
timestamp: May 26, 2018, 07:16:16 pm
content: Quote from: AndyC_772 on May 26, 2018, 05:53:12 pmAnd what the point? Laptop won't consume more than 45W anyway.

author: Gyro
author_rank: Super Contributor
timestamp: May 26, 2018, 07:28:32 pm
content: Quote from: treez on May 26, 2018, 02:49:07 pmRUN treez! Run fast! Run far!Edit: Sorry, I know this has come up before, but if they're too cheap to even buy you solder and basic hand tools...?!

author: ocset
author_rank: Super Contributor
timestamp: May 27, 2018, 09:23:29 am
content: Thanks, virtually all small British electronics companies are being run on tight-as-heck budgets, because the ownersknow that UK is a bad place to start electronics companies, because....1)...The UK trains very very few engineers who are British and will want to stay here after graduating.2)....Property prices in UK are ridiculously high, so a small company simply wont be able to buy a bigger property...unless they go up north, but most business types dont want to go up north....as such, the small uk electronics co's keep their operating costs extremely low, so that they can boast toa potential foreign buyer that it wont cost them much to run....The classic example is a company called Cyden in UK.Cyden is a brilliant once-UK company who invented and then produced its own fantastic technology. They still do.-Yet even they succumbed and sold themselves off to Braun (which is owned by Proctor and gamble).Now Cyden still make fab products...but they are not allowed to put their own name on their own product.Also, they are not even allowed to start any work unless they have cleared it with Braun HQ.Another example is uvintegration.com...they were generating ridiculous amounts of sales but still sold off.Sadly, ML Electronics also went, despite being a fabulous electronics design house.

author: bd139
author_rank: Super Contributor
timestamp: May 27, 2018, 09:53:56 am
content: Flat out the CPU will use about 22W in that machine. 45W is fine. The higher power adapters just mean you can charge at full rate while whipping the CPU.Every time I hear a rant about the U.K. electronics industry I’m glad I bailed out into software years ago. Better cash and even if you’re a contractor there’s enough cash left over to buy very high end kit. If I’m charging hourly I’ll use my slowest machine though

author: Gibson486
author_rank: Frequent Contributor
timestamp: May 30, 2018, 01:48:06 pm
content: Quote from: treez on May 25, 2018, 09:00:58 pm?? is this a joke?

author: JohnnyMalaria
author_rank: Super Contributor
timestamp: May 30, 2018, 03:20:02 pm
content: I had to double-check the date of the first post. Nope, not April 1st.My Yoga 14 has a 65W supply and an Intel i5-6200U @ 2.3GHz. TDP = 15W. It can do some seriously fast multicore number chunking.Stating a minimum power for a supply to run an app is absurd. There are other factors (duh): clock speed, TDP, RAM, SSD vs HDD and so on. The laptop or supply aren't going to melt because a circuit simulator is trying to run fast. Plus, it is very hard (impossible) to write a multithreaded application to use all of the time of all of the cores. I certainly cannot imagine that the LTspice developers bother trying to squeeze every clock cycle for every core out of their code. I suspect the core (sorry) code is old and doesn't make use of the more recent multiple processing APIs. If you use Resource Monitor then you'll see that it doesn't exactly go out of its way to make good use of the cores anyway.EDIT- OP's Yoga 510 (14) is the newer version of mine and should run LTspice like a dream. I've written Python software that makes heavy use of the Numpy mathematics libraries which, in turn, are built onIntel's MKL library. This means super efficient, multithreaded code. I'm still blown away by the speed of the combination of Numpy and my Yoga.

author: SiliconWizard
author_rank: Super Contributor
timestamp: May 30, 2018, 03:45:37 pm
content: Ahah, yes.Anyway, any laptop sold with a PS that wouldn't enable you to make it run at full speed would clearly be a joke IMO.Some ultraportable laptops may come with a small PS that would make charging the battery extremely slow if you run the CPU at full speed, but I've never seen any that would just crash or make the CPU throttle because of that (excessive temperature may lead to this though, but that's another problem). But for serious work, choose a decent laptop. Not one for designing powerpoint presentations while on a plane.Small laptops CPUs usually are much less powerful than desktop ones though (lower multicore max freq, smaller cache, ...), so whereas you can perfectly use LTSpice on those, simulations will be certainly much faster on a decent workstation.

author: Sudo_apt-get_install_yum
author_rank: Regular Contributor
timestamp: May 30, 2018, 04:08:11 pm
content: I’ve got an old HP laptop that I use LTSpice on when I’m out and about. It’s a i5 with 16gb ram and a SSD, LTSpice runs just fine on it and its "just" a 90W power brick too it. It does however stop charging at time since all the power is consumed by the CPU.Don’t think you need to upgrade the power brick for your computer since it’s a low power machine and the manufacturer supplied it with a 45W brick so it should be fine, might stop charging at times like mine under "extreme" load but the CPU on laptops have power limiter (throttle the clock) to consume less power so they don’t exceed more power than they are rated for.

author: Marco
author_rank: Super Contributor
timestamp: May 31, 2018, 11:06:01 am
content: Quote from: SiliconWizard on May 30, 2018, 03:45:37 pmThermal throttling is pretty much the default expectation with modern small form factor laptops, in the old days most decent laptops had good enough cooling to perform nearly the same with the same hardware ... no longer.

author: wraper
author_rank: Unknown
timestamp: May 31, 2018, 06:40:52 pm
content: Quote from: Marco on May 31, 2018, 11:06:01 amModern laptops generally have much better cooling than stupid loud furnaces from a decade ago. On top of that, old CPUs did not have boost clock to drop it to default clock.

author: Ice-Tea
author_rank: Super Contributor
timestamp: May 31, 2018, 07:00:11 pm
content: Quote from: wraper on May 31, 2018, 06:40:52 pmDon't you think those two statements are a bit contradictory? That's the point he was trying to make: thin laptops have relatively poor cooling which means they can not maintain boost clocks for all that long...

author: wraper
author_rank: Unknown
timestamp: May 31, 2018, 07:25:40 pm
content: Quote from: Ice-Tea on May 31, 2018, 07:00:11 pmThin laptops have way better and more silent cooling than likes of HP DV6000, DV9000 series from a decade ago. Not to say, thin laptops usually have U series CPU with 15W TDP.What I mean is that such comparison is misleading. There was no boost clock to keep.And then complain that modern laptops cannot keep that bonus under prolonged load,bonus which you did not have in the past to begin with.And then claim that because of this, old laptops were better.

author: wraper
author_rank: Unknown
timestamp: May 31, 2018, 07:50:15 pm
content: For example my Acer V5 573G from 2014 is 2.1 cm thick, has i5 4210u (15W TDP), GTX850 (45W TDP), 90W PSU. It's completely cool and silent when doing general work, watching videos. When gaming, it becomes a bit warm in the middle and slightly hot at exhausts on the back. Fans are still not that loud. Why so? It has 2 heatsisinks larger than burning hot DV6000 had and 2 fans instead of 1 (like 99% of laptops at that time). Today 2 heatsinks/fans is a norm. Even in ultrathin laptops.

author: montemcguire
author_rank: Regular Contributor
timestamp: July 03, 2018, 05:37:05 am
content: I use LTspice on a laptop, and it is disturbing to make it go into high speed cooling fan mode. One thing you can do in LTspice is to limit the number of parallel threads that it will spawn. In the SPICE tab of the control panel, there is a "max threads" parameter that you can set. On a quad core Intel, the default will be set to eight, to allow you to use all 8 hypercores available from the Intel chip. If you're doing short simulations, then it's fine to leave it set to 8, but for simulations that take a relatively long time to converge or execute, I find it's helpful to scale "max threads" down to a lower value like 2. Modern Intel CPUs do clock boosting, and can also do core hopping, and this makes them very fast with single threaded applications. If you tell LTspice to only launch 2 threads, these can still hop among cores using a boosted clock while still avoiding thermal throttling, without burning up the chip. I haven't directly measured it, but reducing "max threads" from 8 to 2 seems to increase execution times a lot less than the factor of 4 that you'd expect, and makes long simulations much more practical, since the machine won't go into thermal throttling.Laptops thermally throttle, and I find it's best to avoid that region to get better overall performance. Of course, depending upon the tricks your CPU can do, your mileage may vary.

author: montemcguire
author_rank: Regular Contributor
timestamp: July 03, 2018, 05:50:37 am
content: Quote from: JohnnyMalaria on May 30, 2018, 03:20:02 pmWell, you've imagined wrong. LTspice IV is multithreaded, and there's a control panel parameter to set the number of threads used. Further, a good bit of the code is actually stripped of several addressing indirection layers upon execution to increase its speed, just to avoid one more memory indirection layer, basically keeping things closer to the CPU and floating point unit more often. This is true for LTspice IV on MacOS - not sure about the modern version on Windows. It can soak a CPU pretty easily. It's fun to speculate, but sometimes, reality gets in the way. ;-)

author: JohnnyMalaria
author_rank: Super Contributor
timestamp: July 03, 2018, 12:36:01 pm
content: Where did I say it wasn't?My point is that it doesn't make efficient use of the available cores.It isn't a criticism of the software, it's just a fact and it speaks to the odd claim that it somehow requires a powerful power supply.

author: SiliconWizard
author_rank: Super Contributor
timestamp: July 03, 2018, 07:23:55 pm
content: Quote from: montemcguire on July 03, 2018, 05:50:37 amYep, LTSPice IV and XVII both have a multithreaded solver on Windows as well.The actual "efficiency" of the solver's multitheading is of course not optimal. On average it uses approx. 30% to 40% of CPU on my Core i7 (6 cores/12 logical cores), nb of threads set to 12, whereas a single-thread app can use only ~8%, so it's already a very significant improvement over a single-core solver.