Motherboards claiming more VRM phases by using extra inductors  - Page 1
Forum section: electronics / general

author: Back2Volts
author_rank: Unknown
timestamp: April 17, 2019, 12:11:50 am
content: Because I am looking at replacing a 10 yr old computer, I have been studying the current status of the technology, read many posts and watched many videos. The other day I run into a review pointing to a brand as best in VRMs. This afternoon, just by chance I run into a comment about fake VRM phases and from there I googled this video.Guess what brand is claiming the extra phases ? The video is very long because the guy is very mad, but you can get the net of what he is saying in the first few minutes. I have found it interesting... seems to be a troubling move by the industry

author: NiHaoMike
author_rank: Super Contributor
timestamp: April 17, 2019, 12:57:06 am
content: At the end of the day, how well it handles load is all that matters. Start a stress test and take a few thermal images after letting it warm up for a few minutes. Get out the scope and measure the ripple if you really want some data for comparison. Could even get out the clamp meter to get an idea of efficiency as long as other variables are kept under control.

author: magic
author_rank: Super Contributor
timestamp: April 17, 2019, 08:14:03 am
content: It may still be a better VRM because more components is less resistance, if they are equally good. Less resistance is better efficiency and higher power capacity.It will be worse than an 8ph design using the same components in terms of ripple. It may be as good as previous generation 8ph designs if they managed to double frequency.Basically, what NiHaoMike says. Make tests or check out reviews if you want to know how it performs. That's why manufacturers of consumer computer components are notoriously reluctant to publish specs - they don't want laymen comparing things by numbers without understanding what they are doing.

author: Back2Volts
author_rank: Unknown
timestamp: April 17, 2019, 12:40:24 pm
content: The point is that they are advertising twice the phases. The performance consideration would have relevance if they where advertising "it performsasan eight phase VRM". They did not say our fewer phases have lower effective resistance which makes them work as well.What would about placing six spark plugs on top of a four cylinder engine and advertising it as a six cylinder. It would be a lie no matter how much power the engine delivers. The difference is that people are educated enough to know what a cylinder is, but not to know what a phase really is or does.To me is a matter of honesty or lack of it.

author: David Hess
author_rank: Super Contributor
timestamp: April 17, 2019, 01:24:01 pm
content: Quote from: magic on April 17, 2019, 08:14:03 amOr it may be equally good but less expensive to implement.The cost of what Gigabyte did is greater demand on the input and output capacitors because of greater ripple current. Offsetting this, twice (or 1.5 times) as many less expensive power MOSFETs and twice as many less expensive inductors were used and a less expensive controller.But Gigabyte unambiguously lied. These VRMs did not have the advertised number of phases.

author: MrMobodies
author_rank: Super Contributor
timestamp: April 17, 2019, 01:43:39 pm
content: Interesting video and I watched it all the way.When Gigabyte long ago started advertising their boards for gaming and decorating it accordingly along with the other manufacturers I stopped taking them seriously and it put me off. I just preferred them plain with an accurate description of what it can do. I don't mind a bit of decorations in the packaging but I find that over the top now and they state things that are not true.

author: wraper
author_rank: Unknown
timestamp: April 17, 2019, 02:00:33 pm
content: Quote from: MrMobodies on April 17, 2019, 01:43:39 pmIt's a plague which affected basically all manufacturers. Mumbo jumbo RGB dance lights and sorts of crap. Backplates on graphics cards without any thermal interface to PCB (some have it), basically shielding heat. Covers on motherboards, often called armor.

author: MrMobodies
author_rank: Super Contributor
timestamp: April 17, 2019, 02:15:44 pm
content: I remember that board in the picture.That's that Asus Sabertooth series that I read about in the past that had the tracers too near the cpu heatsink mounting holes and some of them got damaged when the screw was tightened too much?The manufacturers then classed it as "Customer induced damage" when they were returned.Edit:It looks like many of them are doing that now.I just found see attachment a Gigabyte Ultra Durable H310M S2P with the tracers right next to the right side of the heatink mounting holes.Not very durableif you over tighten the screws and accidentally break the tracers underneath.

author: thm_w
author_rank: Super Contributor
timestamp: April 17, 2019, 08:48:29 pm
content: Quote from: MrMobodies on April 17, 2019, 02:15:44 pmIntelspecis 4mm PTH and 6mm no route. It looks like they don't even meet the spec. Especially bad on the left side where its easy enough to push the traces further away.Quote from: Back2Volts on April 17, 2019, 12:40:24 pmSure, your point is valid and interesting and they should be called out for it (as Nvidia has been in the past among other examples).But it really has no direct relevance to users when deciding on which motherboard to go with. There are hundreds of other factors in play.

author: NiHaoMike
author_rank: Super Contributor
timestamp: April 17, 2019, 11:01:06 pm
content: Quote from: MrMobodies on April 17, 2019, 02:15:44 pmIt looks like a cheap patch would be some plastic washers glued over the holes.Quote from: wraper on April 17, 2019, 02:00:33 pmMaybe they're trying to target those who don't like the look of nude PCBs.

author: amyk
author_rank: Super Contributor
timestamp: April 18, 2019, 12:55:00 am
content: Quote from: NiHaoMike on April 17, 2019, 11:01:06 pmIn which case... in whichcaseyou put it inside a case.It looks as stupid as those engine covers under the bonnet:https://iedei.files.wordpress.com/2011/04/2010-lexus-ls460-sport-from-engine-view-picture.jpegThis is more like it...https://www.thetruthaboutcars.com/wp-content/uploads/2013/07/1970ChevroletCamaroZ28-engine.jpg

author: MrMobodies
author_rank: Super Contributor
timestamp: April 18, 2019, 01:03:07 am
content: Long ago I once had a Gigabyte 8PENXP and I thought that it wasn't exactly plain but it was decorated enough where they coloured all the slots, like the dimm slots to indicate what modules should go in if singular or a couple and they put a few fancy copper heatsinks and stickers and names over it.I got to look at the marketing material and it'll be interesting to find out if there were any untrue claims but I think the DPS plug in board was there so you can adjust the voltages to work with the newer and older Socket 478 Pentium 4's at the time.Edit:Quote from: NiHaoMike on April 17, 2019, 11:01:06 pmFor the prices they were going at I wouldn't want to bodge on some plastic washer and glue.I might as well go and purchase an EATX server board kit/bundle than one of those.I just did a search and they do it on some the EATX ones as well.See attached Intel S3420GP.

author: Circlotron
author_rank: Super Contributor
timestamp: April 18, 2019, 02:54:55 am
content: Quote from: wraper on April 17, 2019, 02:00:33 pmSimilar to what you see under the bonnet of a car nowadays. All this moulded plastic stuff hiding the real works.

author: David Hess
author_rank: Super Contributor
timestamp: April 19, 2019, 10:38:28 am
content: Quote from: Circlotron on April 18, 2019, 02:54:55 amAnd computer cases - I do not want windows, I do want to be able to filter intake air and pressurize the case to keep dust out, I want lots of room, and I want lots of drive bays. The flashy stuff just gets in the way.

author: Rerouter
author_rank: Super Contributor
timestamp: April 19, 2019, 11:00:29 am
content: If you want the BS kept a minimum, probably look at asrock, if you want none at all, look at supermicro,The part i find the funniest is that a 4 layer PCB can be a marketing feature on some of the modern motherboards.When your running tens to hundreds of various GHz or faster trancievers across 30cm of board area, being able to get away with 4 layers speaks wonders to how tolerant the trancievers and standards are.

author: nctnico
author_rank: Super Contributor
timestamp: April 19, 2019, 04:19:33 pm
content: Quote from: Rerouter on April 19, 2019, 11:00:29 amNo, buy a professional workstation from HP or Dell. At least these have a real thermal design. The plastic which is in these is mostly air ducts to divert the air flow through the case along the hottest parts.

author: wraper
author_rank: Unknown
timestamp: April 19, 2019, 04:36:19 pm
content: Quote from: nctnico on April 19, 2019, 04:19:33 pmBut you'll pay way more just to avoid those bells and whistles. Temperature still likely will be worse than in half decent custom build.

author: magic
author_rank: Super Contributor
timestamp: April 19, 2019, 04:45:10 pm
content: Quote from: nctnico on April 19, 2019, 04:19:33 pmWhenever I look at those things, they also have non-ATX motherboards and PSUs, implying you need to buy a new special snowflake case and PSU with every upgrade.Thermal design isn't much of an issue for me. Intake at front bottom, exhaust at rear top, it works every time.

author: nctnico
author_rank: Super Contributor
timestamp: April 19, 2019, 05:02:58 pm
content: Quote from: wraper on April 19, 2019, 04:36:19 pmWith this statement I assume you've never taken a professional workstation apart. A 'custom build' still means using standard components and a case which aren't optimised for airflow or to even work together. Professional workstations are in a different league. This is a picture of the system I have:There are 3 fans in the front and the PSU fans draw air through the lower drive bay. This system is whisper quiet and keeps temperatures well within the operational limits. These are the kind of systems you get 5 to 10 years of reliable operation from. But I don't care about the number of phases the VRM has though.

author: wraper
author_rank: Unknown
timestamp: April 19, 2019, 05:09:08 pm
content: Quote from: nctnico on April 19, 2019, 05:02:58 pmI've taken apart. And CPU cooler most likely will be way worse than half decent cooler for custom built. With in/out fans there won't be hot air accumulation either. The only thing you'll achieve with air ducts is using less fan count to do the same job.BTW GPU on the picture has garbage cooling.

author: nctnico
author_rank: Super Contributor
timestamp: April 19, 2019, 05:19:01 pm
content: This isn't a gaming rig so the graphics card isn't an high-end one and therefore doesn't need much cooling. In my system I have an even smaller/lower spec graphics card which doesn't need the external 12V power cable.And sure ducting does a better job of cooling and needing less fans makes the system more quiet (and accumulate less dust). Before this system I had a standard case and one of the problems with it was that de CPU would overheat after a while due to accumation of dust in the CPU heatsink. Positive or negative pressure didn't make a difference and the fan noise was driving me nuts.

author: 0culus
author_rank: Super Contributor
timestamp: April 19, 2019, 05:21:17 pm
content: Quote from: wraper on April 17, 2019, 02:00:33 pmI had one of the early ones from ASUS in my old build. It was intended that you installed a small fan in the space where that blank is between the first PCI and the socket. If you didn't...well that was your problem.

author: wraper
author_rank: Unknown
timestamp: April 19, 2019, 05:39:00 pm
content: Quote from: nctnico on April 19, 2019, 05:19:01 pmMultiple fan noises don't add up much. It will be a little bit worse than loudest of the fans. And your system was garbage. Decent cases have dust filters and decent coolers have quite large gaps between heatsink fins so barely any dust accumulates on those. I recently looked on CPU fan in my PC. After 1.5 years of use, no dust on CPU heatsink, although my apartment accumulates quite a lot of dust.

author: hans
author_rank: Super Contributor
timestamp: April 19, 2019, 05:39:35 pm
content: GamersNexus YT often does VRM analysis of "high-end" graphics cards and motherboards.Doublers are also a thing. You take a 6-phase controller IC, and basically feed that PWM to 2 gate drivers at half the frequency, and voila! More phases..But it doesn't increase the PWM resolution or actually change the phase.. it just adds more output stages. Those output stages may share the current, and since P=I^2 * R, things will run less hot & more efficient. But not with a tighter line or load regulation.

author: wraper
author_rank: Unknown
timestamp: April 19, 2019, 05:46:21 pm
content: Quote from: hans on April 19, 2019, 05:39:35 pmYou are completely wrong in this. It does double phase number. In it's true meaning, and outputs of those doublers have phase shifted. There is no lie in it. It does not add individual control and current sensing of those phases though if PWM controller/doublers are dumb. Or may if controller/doublers are smart.

author: hans
author_rank: Super Contributor
timestamp: April 19, 2019, 06:28:42 pm
content: I think it depends on the definition of a phase.More output stages, lower current per stage, less resistive losses, less heat and higher efficiency.The doublers create a mirrored control pair such that both filters can be interleaved with less ripple. If that's what you qualify as phase, then you're right.But in my view, the controller is still generating a fixed resolution PWM at the same frequency, and thereby not really improving the regulation properties of the power supply, apart from benefits gained of the lower resistive components that are now present in the effective output stages.

author: james_s
author_rank: Super Contributor
timestamp: April 19, 2019, 06:43:11 pm
content: I didn't know the number of VRM phases was even a thing that was marketed. Certainly all I've ever cared about is whether the board can adequately and reliably power the CPU and other components. Whether it has a single VRM phase or 20 makes no difference to me.

author: wraper
author_rank: Unknown
timestamp: April 19, 2019, 07:11:47 pm
content: Quote from: james_s on April 19, 2019, 06:43:11 pmWell, it's important thing actually. if you go with low phase count, they need to be ridiculously beefy to offer same performance and reliability. Try to get 200 amps with tiny ripple from a single phase.

author: james_s
author_rank: Super Contributor
timestamp: April 19, 2019, 07:59:30 pm
content: It's important to the engineers designing the board, but it makes no difference at all to the end user. Provided it performs adequately I can think of no reason why the consumer would care whether it had a lot of VRM phases or a magical spell to make it work. To the end user a motherboard is a black box, it either works or it doesn't, they don't have to care how it does what it does.

author: wraper
author_rank: Unknown
timestamp: April 19, 2019, 08:05:12 pm
content: Quote from: james_s on April 19, 2019, 07:59:30 pmIf they overclock, it makes difference. Both in overclocking potential and not emitting magic smoke in the process. Also if you try to run high end cpu on motherboard with low phase count, you'll likely to have problems. On top of that weak VRM have low efficiency and produce a lot of heat at higher loads. Phase count is basically the only benchmark not too technically savvy people can use to estimate VRM performance.

author: james_s
author_rank: Super Contributor
timestamp: April 19, 2019, 10:02:16 pm
content: But again you're looking at this from the standpoint of an engineer. Having more VRM phases is typically the technique utilized to obtain the required performance, but to the end user this is irrelevant. All that matters is does it perform, period. Whether it gains the required performance parameters through having a certain number of VRM stages or through some other means makes absolutely no difference at all *to the user*.Consider this, imagine for a moment that some hypothetical technological development enables a single phase VRM to deliver better performance than the best polyphase VRMs on the market today, higher current capability, better transient response, higher efficiency, lower noise, it can do anything we want because it's hypothetical. Are you going to argue that a 6 phase VRM using the existing technology is superior because it has more phases?There is simply no reason for a consumer to care what regulator topology is used provided it delivers the required performance. 99% of the population wouldn't know what a VRM is if you placed one in their hand. Numbers like the number of phases are pure marketing drivel. A poorly designed VRM with 20 phases could easily be inferior to a well designed one with 3 phases, the number on its own tells you nothing.

author: Rerouter
author_rank: Super Contributor
timestamp: April 19, 2019, 10:22:54 pm
content: There is a trade off between better built VRM phases and the number of phases, for the consumer having more VRM phases is more likely to reduce the power consumption of the motherboard, as it means it can scale back the number of active phases at lower consumption, (PWM width limits)And Re: work stations, If its for a company and your spending thousands for it, you use a supplier with local locations / spare parts stock for replacements, and let them worry about the airflow.If its a semi personal PC / Workstation, if you can live with unbuffered ECC, you can get a very beefy threadripper workstation for much less, that uses standard parts, that can generally be replaced at any local store.

author: wraper
author_rank: Unknown
timestamp: April 19, 2019, 10:34:20 pm
content: Quote from: james_s on April 19, 2019, 10:02:16 pmBut it's certain that with low phase count, like 3, motherboard is crap. Nobody in sane mind will make 3 especially good phases. It's cheaper to achieve better performance with say 5 phases. Cheaper semiconductors and inductors can be used. There will be less ripple current, and lower requirements to output capacitors. Phase quality can vary, but it's completely true that more phases is better, it's a general trend of how things go. When it gets to ridiculous number, there won't be positive effect from that. But you still can expect that VRM performance will be among the best. The only downsides are high price and reduced efficiency at light loads.

author: NiHaoMike
author_rank: Super Contributor
timestamp: April 19, 2019, 11:27:10 pm
content: Quote from: james_s on April 19, 2019, 10:02:16 pmWith GaN, it's not even that hypothetical.

author: Buriedcode
author_rank: Super Contributor
timestamp: April 19, 2019, 11:40:17 pm
content: I dont' get it. If it powers the CPU just fine, then why does it really matter if the mobo manufacturer over-does the marketing? Computer parts, especially "gaming" ones have always been a bit over zealous with marketing, but I'm not sure who would pick one motherboard over the other based on how many phases its CPU power supply had - surely it is about actual features that the user requires.In the video, it looked like a "premium" motherboard he was talking about, that are essentially cheaper motherboards, with a few extra bells and whistles and more marketing wank. It is aimed at those who enjoy throwing money at a PC build (nothing wrong with that, we all need a hobby), and to justify the extra cost a lot of unnecessary things are added, like the colour of components and connectors etc..Now, if gigabyte skimped on parts that put the CPU at risk, or just ended up being unreliable, I'd understand. But frankly I don't care how many phases my motherboards PSU uses as long as it works, and lasts.

author: nctnico
author_rank: Super Contributor
timestamp: April 19, 2019, 11:49:46 pm
content: Quote from: Buriedcode on April 19, 2019, 11:40:17 pmIt is very close to audio-phoolery.

author: wraper
author_rank: Unknown
timestamp: April 19, 2019, 11:52:23 pm
content: Quote from: Buriedcode on April 19, 2019, 11:40:17 pmWhen high side MOSFET fails open, your CPU/GPU very likely will be gone. VRM do fail, it's not something unusual, and more stressed they are, the more often. If you put power hungry CPU onto motherboard with 3 phase, or crappy 4 phase VRM, quite likely it will eventually fail. Especially if you try overclocking.Also note that Buildzoid does extreme overclocking, including LN2, so phases for him is quite a thing.

author: wraper
author_rank: Unknown
timestamp: April 20, 2019, 12:12:28 am
content: Also note that motherboards where VRM phase count is emphasized usually are marketed as boards for overclocking. Where "it just works" is not a thing as result is directly dependent on particular board. Sort of analog performance in digital device.

author: tooki
author_rank: Super Contributor
timestamp: April 20, 2019, 04:40:17 pm
content: If the number of voltage regulator phases mattered, it’d be a critical specification in every DC-DC converter spec, yet it’s not. As others have already said, all that matters is whether it meets its specs. How it does that is absolutely irrelevant.

author: Buriedcode
author_rank: Super Contributor
timestamp: April 20, 2019, 05:00:21 pm
content: Quote from: wraper on April 19, 2019, 11:52:23 pmAhh ok, so its a reliability thing. I didn't see that in the video - it was pretty long and I skipped quite a bit so I must have missed it. If it fails more often, or causes issues under normal conditions - no overclocking, then of course, thats pretty shit. If one over-clocks, then surely thats a risk the user takes. It does seem though, that motherboards are promoted/advertised as being specifically for overclocking.I gave up following the finer details of motherboards years ago. Back when people felt the need to see specific temperatures in various parts of their rig, and manually adjust fan speeds (pretty pointless).Quote from: nctnico on April 19, 2019, 11:49:46 pmWell, with audio you have people claiming they "hear" a difference when there probably isn't one, whilst much of it is easily debunked there is always a subjective element which is what keeps that crap going. I'm not sure there is such a thing with PC's. I have never heard anyone claim they "feel" a difference in a PC's performance because of VRM phases as it is all numbers, and can easily be benchmarked. But I guess if one is pushing the hardware to its absolute limit then these things are important to those users. My point is, very few are actually that kind of user.

author: james_s
author_rank: Super Contributor
timestamp: April 20, 2019, 05:28:30 pm
content: It it gains reliability by adding more phases great, add more phases, but if someone finds a way to get the needed reliability through other means then the goal has been met. The only thing that matters is the performance the circuit delivers. This is all no different than back in the day when marketing proudly printed the number of transistors on the front of a radio. In some cases a radio with more transistors offered better performance but this was by no means always the case, the number of transistors is irrelevant and nothing more than marketing drivel, the only thing that matters is the actual performance the radio delivers, the means through which it accomplishes this makes no difference to the user.The number of phases is still irrelevant to the end user, period, there is no debate.

author: nctnico
author_rank: Super Contributor
timestamp: April 20, 2019, 05:44:34 pm
content: Quote from: tooki on April 20, 2019, 04:40:17 pmI couldn't agree more. A design meets specifications or not regardless how it is constructed. Without doing a very thourough analysis based on the actual components being used you can't say anything sensible based on just looking at the implementation. The first post seems to indicate dummy (non-working) components are added to motherboards to make the design look like it is adhering to thegrazy number du jour. Hence my comparison with audio phoolery. If you want to be fooled someone will happily collect your money.

author: wraper
author_rank: Unknown
timestamp: April 20, 2019, 10:28:23 pm
content: Quote from: nctnico on April 20, 2019, 05:44:34 pmThey are not dummy components. They just place components in a way there seem to be more phases than actually are. 2 inductors, 2 mosfets paralleled. BTW 1 high side mosfet and 2 low side mosfets is quite common in real phases with only one inductor as well. Low RDS(on) on the low side is very important for efficiency. FWIW using same components as in those 1 phase looking like 2 phases they could were well make completely real phases if more expensive PWM controller was used.

author: nctnico
author_rank: Super Contributor
timestamp: April 20, 2019, 11:12:13 pm
content: Sorry but it is utter nonsense do disqualify a design because simply it uses components in parallel (or not). There is always a cost versus benefit which doesn't affect the required performance of the design.

author: wraper
author_rank: Unknown
timestamp: April 20, 2019, 11:16:13 pm
content: Quote from: nctnico on April 20, 2019, 11:12:13 pmIt's not disqualifying the design. It's pointing out dishonest claims from manufacturer. If those were real phases with same power components, as minimum VRM would have more stable output voltage (given that design wasn't screwed up).Not to say with such fake phases, they often simply place in parallel two mosfets with relatively poor RDSon instead of one top notch mosfet.

author: nctnico
author_rank: Super Contributor
timestamp: April 20, 2019, 11:43:45 pm
content: Quote from: wraper on April 20, 2019, 11:16:13 pmYou can't say this without analysing the circuit (how is the loop stabilised?)QuoteWhich is a cost versus benefit decission which doesn't affect the performance of the circuit. Actually having two seperate MOSFETs helps with getting rid of the heat over a bigger surface area. So the choice may also be driven by the thermal design parameters. If you use two parallel MOSFETs with twice the RDson compared to a 'better' MOSFET you'll dissipate way less power. P=I^2*R. If the current is half then the power becomes a quarter. Also the gate charge required for a lower RDson MOSFET is likely larger so you'll have more switching losses. Choosing the optimal types and configuration of MOSFETs for a switching power suppy is an art in itself.

author: james_s
author_rank: Super Contributor
timestamp: April 21, 2019, 12:21:52 am
content: Well at least this thread illustrated precisely why a spec like the number of VRM phases is listed in the marketing data and some unscrupulous manufactures take the trouble to fake additional phases - some people obviously think it matters and shop accordingly.Personally I'm going to continue to shop based on performance evaluations and recommendations of reviewers I trust. I don't really care whether it has a zillion VRM stages or magical pixie dust as long as it performs adequately.

author: wraper
author_rank: Unknown
timestamp: April 21, 2019, 01:35:30 am
content: Quote from: nctnico on April 20, 2019, 11:43:45 pmWhich is deception in the nutshell. Buyer is supposed to think those are real phases with decent mosfets in each phase but they are fake phases with 2 not so good mosfets per actual phase.QuoteBy this logic, if those were real 8 phases with good mosfets, it would dissipate half of the heat compared with 8 fake (4 real) phases with crap mosfets.QuoteIf that was a real phase, you would have half of the gate charge per channel to drive. So you can use beefier mosfets with higher gate charge.

author: David Hess
author_rank: Super Contributor
timestamp: April 21, 2019, 07:59:00 pm
content: Quote from: james_s on April 21, 2019, 12:21:52 amMarketing is paid to lie and deceive. It is fair to castigate companies for this behavior.Transistor radios used to be marketed by the number of transistors even if superfluous transistors were added to inflate this number. Watches used to be marketed by the number of jewel bearings. Prosecutors will inflate their conviction numbers in a variety of illegal and unconstitutional ways. It is an old game.

author: Kleinstein
author_rank: Super Contributor
timestamp: April 21, 2019, 08:38:23 pm
content: The conclusions in the video may be too fast. It may still be just marketing / fake phases, but without actually looking at the board, it could still be true 8 phases. As Warper showed with the picture, there are actual chips to double the phases, possibly combined with gate drive. So there is a very real option to use a 4 phase controller (running at twice the speed) and use 4 phase doubling gate drivers to get 8 real phases.Those MOSFET chips sometimes have more than one MOSFET in a case - so the high side switch could actually contain two MOSFETs. Those are used only with a smaller duty cycle and thus produce less heat than the low side FETs. So one could get away with the 2 FETs in one case here.So without really looking at the chips and MOSFETs it's a premature conclusion.

author: wraper
author_rank: Unknown
timestamp: April 21, 2019, 08:45:42 pm
content: Quote from: Kleinstein on April 21, 2019, 08:38:23 pmDid you actually watch the video? All of that is completely in parallel - mosfets, inductors. And particular controller chip discussed in the video cannot be used with doublers.

author: David Hess
author_rank: Super Contributor
timestamp: April 21, 2019, 09:18:12 pm
content: I took a second look to be sure. There are only two external drivers on the motherboard which is consistent with a 4 phase design using the ISL95712. Two of the phases are missing anything which could be a driver or phase doubler which is also consistent with the ISL95712 which directly drives two of the phases.It looks like Gigabyte simply doubled up on the number of inductors placing them in parallel pairs and counted each individual inductor as a phase.Quote from: wraper on April 21, 2019, 08:45:42 pmI am not so sure of that but in this case, there is no evidence that doublers were used. Everything is consistent with a 4 phase design based on the ISL95712 with the expected two external drivers and two phases being driven directly.

author: wraper
author_rank: Unknown
timestamp: April 21, 2019, 09:22:29 pm
content: Quote from: David Hess on April 21, 2019, 09:18:12 pmYou cannot place doublers on gate drive outputs, that's what I mean.

author: Kleinstein
author_rank: Super Contributor
timestamp: April 21, 2019, 09:36:53 pm
content: I watched the video, and it looks like the reason he thinks the inductors and FETs are in parallel is from just looking at the controller chip and concludes that it can not control more phases. For the the smaller "drivers" he is already guessing, using likely.He offered different possibilities on which MOSFETs might be controlled directly from the controller - this suggests there was no real measurement to show they are actually in parallel.So he is missing out the proof, by showing there are no phase doublers involved.The controller chip looks a little odd, having some power drivers included. I am still not convinced it could not be used together with phase doublers. It would be an odd solution, but I don't think it's impossible.

author: wraper
author_rank: Unknown
timestamp: April 21, 2019, 10:07:04 pm
content: Quote from: Kleinstein on April 21, 2019, 09:36:53 pmYou would need to convert MOSFET gate drive back to PWM output and only then use doublers, that's unfeasible. If you look at pictures, it's quite obvious that those are in parallel. It's the same on Asrock mobo in PC I'm now typing from. Also I 'd like to see how you will make 2 phases with 3 mosfets as in the worst case shown.QuoteNot odd at all. Output phase count is configurable. If you need only one or two phases, you don't need external drivers. If you need more you can do this with additional gate driver. Gate drivers need to be quite beefy, so it takes a lot of die space. Also it saves some pin count, allowing to use smaller package.

author: David Hess
author_rank: Super Contributor
timestamp: April 22, 2019, 08:48:26 pm
content: Quote from: Kleinstein on April 21, 2019, 09:36:53 pmIt is common with multi-phase VRM controllers. In some cases the controller's package lacks enough pins for a complete set of gate drivers. Gate drivers also take up a lot more die space increasing fabrication costs. But I wonder if there is also a layout issue where it is better to use an external driver for the most distant power transistors.Quote from: wraper on April 21, 2019, 10:07:04 pmI do not think converting the signal level would be difficult but why bother?I do not understand how the current sensing is handled when doublers are used. Poorly? They were not available when I last designed a multi-phase converter.Update: IR has an application note showing them sensed in parallel. Sure, why not?QuoteThe high side transistor operates at a much lower duty cycle so conceivably the same package might be used to hold a dual transistor; so the low side MOSFET is still larger being one per package but only three packages are required.

author: wraper
author_rank: Unknown
timestamp: April 22, 2019, 08:55:27 pm
content: Quote from: David Hess on April 22, 2019, 08:48:26 pmIf power MOSFET package holds 2 MOSFETs, they have drain and source connected together. Not 2 independent MOSFETs. Not to say there were no doublers on that PCB.

author: David Hess
author_rank: Super Contributor
timestamp: April 22, 2019, 09:24:58 pm
content: Quote from: wraper on April 22, 2019, 08:55:27 pmNo, not all dual packaged MOSFETs have common pins. Symmetrical parts like theSiliconix SI4204were what I was thinking of but asymmetrical parts for phase shedding applications also exist with completely independent transistors.

author: wraper
author_rank: Unknown
timestamp: April 22, 2019, 09:51:48 pm
content: Quote from: David Hess on April 22, 2019, 09:24:58 pmSO-8 is not suitable for modern motherboard VRM. All of those have metal pad on the bottom. That's the issue placing 2 independent MOSFETs in such package.

author: David Hess
author_rank: Super Contributor
timestamp: April 22, 2019, 11:03:05 pm
content: Quote from: wraper on April 22, 2019, 09:51:48 pmI found a bunch like that which also had completely separate transistors but the SO-8 part was a better example. They had dual pads on the bottom which were isolated from themselves.

author: wraper
author_rank: Unknown
timestamp: April 22, 2019, 11:13:01 pm
content: Quote from: David Hess on April 22, 2019, 11:03:05 pmAll I've seen with dual pads contain 2 mosfets connected together. Specially made for VRM, top MOSFET being weaker. One pad for Vin, another pad for GND. Like this one.https://xdevs.com/doc/xDevs.com/ocg_1080/NTMFD4C85N-D.PDF

author: tszaboo
author_rank: Super Contributor
timestamp: April 22, 2019, 11:40:59 pm
content: Look, this is the efficiency of a DC-DC converter:What matters is that in the high load region, the efficiency drops with the load current. If you add a phase, you can reduce the load current from 800mA (in this case) to 400, and get higher efficiency, and less losses. Also, you need smaller input and output capacitors, because the ripple current is less. They entire high power DC-DC is just playing with:CostRdsESRInductor DC resistance and peak current

author: David Hess
author_rank: Super Contributor
timestamp: April 22, 2019, 11:58:19 pm
content: Quote from: wraper on April 22, 2019, 11:13:01 pmThose are more common but completely independent dual devices also exist.Quote from: NANDBlog on April 22, 2019, 11:40:59 pmNobody is debating the merits of poly-phase switching regulators and if they are, they are wrong. They have a lot of advantages and are the most economical solution as well. The question is about what Gigabyte was doing.

author: james_s
author_rank: Super Contributor
timestamp: April 23, 2019, 12:26:28 am
content: What I was debating is whether the absolute number of phases matters. All else being equal having more phases will help to a point, but all else is not equal and the number of phases alone tells you nothing.

author: David Hess
author_rank: Super Contributor
timestamp: April 23, 2019, 02:35:05 am
content: Quote from: james_s on April 23, 2019, 12:26:28 amI do not think the VRM specifications can even be met at this point without a multi-phase converter at least with silicon technology. But the same could be said about using the best aluminum electrolytic capacitors instead of ceramic or polymer electrolytic capacitors. The manufacturers did not switch to polymer electrolytic capacitors for cost reasons; they switched because there was no other way to get the needed performance and reliability.Above the number of phased needed to meet the VRM specifications, it becomes an economics game. Over-specifying the converter may have the advantage of derating the individual parts for better reliability. More phases also means easier heat sinking because the power dissipation is spread out over a larger area. In a portable or space limited design, they might use more phases than strictly neccessary because the individual lower power parts have a shorter profile.

author: ejeffrey
author_rank: Super Contributor
timestamp: April 23, 2019, 03:14:17 am
content: Quote from: hans on April 19, 2019, 05:39:35 pmI'm not sure what you mean here. AFAIK, those doublers essentially alternate pulses between their two output phases. Thus, you can adjust the pulse width at the controller frequency but only switch the MOSFETs at half that. So you should get the improved ripple and regulation of a higher frequency controller with the switching losses of a lower frequency MOSFET. Which is basically the point of a multi-phase converter: if you could run the modulator at 1 GHz you wouldn't really need multiple phases. Even if the controller or doubler does something "dumb" and can't individually vary the pulse width on the two channels you would still get ripple improvement.

author: nctnico
author_rank: Super Contributor
timestamp: April 23, 2019, 10:28:20 am
content: Quote from: David Hess on April 23, 2019, 02:35:05 amStill you have to ask yourself whether reliability and over-engineering are high on the list of designs intended for the consumer market.

author: schmitt trigger
author_rank: Super Contributor
timestamp: April 23, 2019, 01:12:47 pm
content: In these applications unfortunately, buzzwords and catchphrases DO contribute to marketing.Many people just repeat them without understanding their meaning or benefit.A true story;A while back I was having dinner with some acquaintances. One of them is a passionate gamer and loooooves the technology used on it, without actually understanding it.He was mentioning that such and such motherboard, had all these terabytes and gigahertz, massive parallelism, multicores, etc, when I casually asked him: "Do you know what a gigahertz is?"Without losing a beat, he replied: "Sure, the memory size."So I fired back: "And exactly what size is a gigahertz?"A pair of seconds of uncomfortable silence, but then he replied: "Lots and lots of hertz."So.... if a gadget manufacturer finds out that by using certain buzzword tricks,will help him sell additional product, you know it will.

author: David Hess
author_rank: Super Contributor
timestamp: April 24, 2019, 07:28:35 pm
content: Quote from: ejeffrey on April 23, 2019, 03:14:17 amThe doubler halves the switching frequency halving the individual switching and conduction losses but with twice as many of the same device, the total losses remain the same; the dissipation is over twice the area though. If the frequency is then doubled, the switching losses double and the conduction losses remain the same (pulse width is halved to maintain the same duty cycle) implying that a smaller devices with higher conduction and lower switching losses would be more optimal.The big advantage is that with each stage carrying half the current, inductive parasitic effects are halved and physically smaller components may be used to further lower parasitics. Physical construction requirements are eased.A higher switching frequency can also allow for a better transient response which may be difficult to achieve otherwise.Quote from: nctnico on April 23, 2019, 10:28:20 amThey are not but ... that does not stop the user from doing the derating themselves by buying a motherboard originally intended for an overclocking application where the VRM was designed to handle higher currents outside of the specifications given by the processor manufacturer. The user can also select a higher power ATX power supply than strictly necessary for the same reason. And implement "more than enough" processor cooling.Overclockers provide a valuable service by supplying demand for higher performance parts making them more economical.Quote from: schmitt trigger on April 23, 2019, 01:12:47 pmAt least it was not lots and lots of hurts. Or did it?

author: nctnico
author_rank: Super Contributor
timestamp: April 24, 2019, 08:30:23 pm
content: Quote from: David Hess on April 24, 2019, 07:28:35 pmThat would only be true if the motherboard had a clear specification on the maximum power the VRM is designed for (actually VRM is wrong here because the circuit isn't on a module). For kicks I downloaded the manual of one of the motherboards featured in the video but there is no specification for what the CPU power supply can deliver.

author: David Hess
author_rank: Super Contributor
timestamp: April 24, 2019, 09:08:46 pm
content: Quote from: nctnico on April 24, 2019, 08:30:23 pmI have seen some specify supported VRM output current in one way or another.

author: tooki
author_rank: Super Contributor
timestamp: April 24, 2019, 10:32:31 pm
content: Quote from: schmitt trigger on April 23, 2019, 01:12:47 pmReminds me of two incidents I overheard at a Best Buy and Circuit City in the early 00’s, one where where I overheard a customer ask for help with a “digical camera” and another who asked about how many “megapickles” a camera had...I love pickles, a lot. But a megapickle is too much even for me!!