Forums

pc motherboard grounds

Started by John Larkin August 25, 2012
On Sat, 25 Aug 2012 17:44:16 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

>On Sat, 25 Aug 2012 15:09:16 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: > >>On Sat, 25 Aug 2012 10:31:03 -0700, John Larkin >><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >> >>>On Sat, 25 Aug 2012 10:14:48 -0700, Jim Thompson >>><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >>> >>>>On Sat, 25 Aug 2012 10:03:49 -0700, John Larkin >>>><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >>>> >>>>>On Sat, 25 Aug 2012 09:40:54 -0700, Jim Thompson >>>>><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >>>>> >>>>>>On Sat, 25 Aug 2012 09:34:54 -0700, John Larkin >>>>>><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >>>>>> >>>>>>> >>>>>>> >>>>>>>The mounting holes on PC motherboards: are they usually connected to >>>>>>>the PCB ground plane? >>>>>> >>>>>>depends. Are you wearing them like you should ?:-) >>>>>> >>>>>> ...Jim Thompson >>>>> >>>>>You never actually say anything with content any more. You don't even >>>>>discuss circuits in any intelligent way. You've become a useless old >>>>>hen. >>>> >>>>And your WORKING circuits are WHERE ?:-) >>>> >>>> ...Jim Thompson >>> >>>A few are here: >>> >>>http://www.highlandtechnology.com/index.shtml >>> >>> >>>Any your fast current source is where? You can't do it! >>> >>>I rather liked the mosfet-bipolar cascode with Ib correction, but you >>>didn't. What did you find wrong with it? I mean, aside from the fact >>>that I invented it. Are you claiming that this *won't* work? >>> >>>https://dl.dropbox.com/u/53724080/Circuits/Isrc_Ib_2.JPG >>> >>> >>>But I have a couple of better, cuter circuits by now. Show us your >>>approach, and then I'll post a couple more of mine. >>> >>>You never say anything substantive about electronics lately. You can't >>>invent circuits any more. Go back to sci.electronics.basics where >>>amateurs belong. >> >>Show some LTspice .ASC files that can be checked. Then people will >>believe your claims. >> > >That's silly. If you can't look at a circuit and understand it, and >decide how well it will work, and you need a simulator to do your >thinking for you, then you are an amateur. I wouldn't Spice anything >this simple. > >Good grief, you *don't* understand my circuit!
You _do_ know how to make people snicker behind your back. Show us your final solution already... otherwise everyone knows you're exactly as your "friends" relate, "Sawed-off runt with a Napoleonic complex". (Must be nice to have "friends" like that :-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
On Sat, 25 Aug 2012 17:53:41 -0700 (PDT), Bob Boblaw
<larrymoencurly@my-deja.com> wrote:

>On Saturday, August 25, 2012 9:34:54 AM UTC-7, John Larkin wrote: > >> The mounting holes on PC motherboards: are they usually >> connected to the PCB ground plane? > >I haven't seen a mounting hole that was plated-through, but any copper rings surrounding a hole was always (?) connected to ground. OTOH other copper foil running right next to the hole isn't always ground, and I've measured 5V and 3.3V on some; in one case the copper on the left side of the hole was connected to the 5V supply and the copper on the right went the 3.3V (FIC brand PA-2007 or VA-503+ motherboard)
I wonder why they are not plated. A non-plated hole is a secondary PCB fab operation. The ring+vias thing looks like more work. Maybe they are worried about stress/cold flow fracturing the plating? We do plated mounting holes, no extra vias, grounded to internal planes, and I've never seen a problem. -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
On Sat, 25 Aug 2012 17:57:38 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

>On Sat, 25 Aug 2012 17:44:16 -0700, John Larkin ><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: > >>On Sat, 25 Aug 2012 15:09:16 -0700, Jim Thompson >><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >> >>>On Sat, 25 Aug 2012 10:31:03 -0700, John Larkin >>><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >>> >>>>On Sat, 25 Aug 2012 10:14:48 -0700, Jim Thompson >>>><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >>>> >>>>>On Sat, 25 Aug 2012 10:03:49 -0700, John Larkin >>>>><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >>>>> >>>>>>On Sat, 25 Aug 2012 09:40:54 -0700, Jim Thompson >>>>>><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >>>>>> >>>>>>>On Sat, 25 Aug 2012 09:34:54 -0700, John Larkin >>>>>>><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >>>>>>> >>>>>>>> >>>>>>>> >>>>>>>>The mounting holes on PC motherboards: are they usually connected to >>>>>>>>the PCB ground plane? >>>>>>> >>>>>>>depends. Are you wearing them like you should ?:-) >>>>>>> >>>>>>> ...Jim Thompson >>>>>> >>>>>>You never actually say anything with content any more. You don't even >>>>>>discuss circuits in any intelligent way. You've become a useless old >>>>>>hen. >>>>> >>>>>And your WORKING circuits are WHERE ?:-) >>>>> >>>>> ...Jim Thompson >>>> >>>>A few are here: >>>> >>>>http://www.highlandtechnology.com/index.shtml >>>> >>>> >>>>Any your fast current source is where? You can't do it! >>>> >>>>I rather liked the mosfet-bipolar cascode with Ib correction, but you >>>>didn't. What did you find wrong with it? I mean, aside from the fact >>>>that I invented it. Are you claiming that this *won't* work? >>>> >>>>https://dl.dropbox.com/u/53724080/Circuits/Isrc_Ib_2.JPG >>>> >>>> >>>>But I have a couple of better, cuter circuits by now. Show us your >>>>approach, and then I'll post a couple more of mine. >>>> >>>>You never say anything substantive about electronics lately. You can't >>>>invent circuits any more. Go back to sci.electronics.basics where >>>>amateurs belong. >>> >>>Show some LTspice .ASC files that can be checked. Then people will >>>believe your claims. >>> >> >>That's silly. If you can't look at a circuit and understand it, and >>decide how well it will work, and you need a simulator to do your >>thinking for you, then you are an amateur. I wouldn't Spice anything >>this simple. >> >>Good grief, you *don't* understand my circuit! > >You _do_ know how to make people snicker behind your back. > >Show us your final solution already...
That's it. Anybody half competant should be able to write in the parts values, immediately, without even needing a calculator. It's not worth simulating because the low frequency behavior is obvious and the GHz bits don't sim usefully because the transistor models aren't there. Why don't you design a fast current source? Because you can't! You *don't* understand my circuit! -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
On Sat, 25 Aug 2012 09:34:54 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

>The mounting holes on PC motherboards: are they usually connected to >the PCB ground plane?
I just checked about 8 assorted motherboards I had sitting in the pile with an ohms-guesser. All the mounting pads are connected to the ground pins on the power connector. There may be some isolated grounds but certainly all the power grounds appear to hit the mounting hole grounds. However, way back in the pre-ATX style motherboard era, mounting was done using plastic insulating spacers. The motherboard was still grounded, but usually only with one brass standoff and screw. That made it difficult to pass various EMI specs and probably inspired the current multiple ground ATX design. Digging through my PC104 board pile, my ohms-guesser finds a mix of grounding philosophies. Some have plastic spacers, others metal. Some have mounting pads that are connected to the power supply ground pins, while others are isolated. This might explain: <http://smallformfactors.com/pdfs/RTD.Win07.pdf> EDITOR: Should the pads for the PC/104 mounting holes be grounded? BLAZER: The PC/104 specifications do not say anything about grounding the mounting holes. Some PC/104 manufacturers ground them, others leave them unconnected, and still others provide an option to ground them. Deciding whether or not to ground mounting holes and cases is a system design issue. You must have a good ground with no loops to ensure the best performance, but some applications may require complete isolation. In practice, if a board has the mounting holes grounded, nylon spacers can be used to isolate them. If the mounting holes on a board are not grounded, a metal spacer will carry ground through to the other cards in the system. I also checked the ATX 2.3 power supply spec and found nothing about board grounding. I also checked a few schematics of various ATX style motherboards, but didn't find anything showing isolated mounting pads, floating grounds, or multiple ground/earth symbols. -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
On Sat, 25 Aug 2012 12:42:27 -0700, SoothSayer
<SaySooth@TheMonastery.org> wrote:

> Bullshit. You could not name even a single MOBO that has isolated >mount holes. It world fail to comply with the spec, and no maker ever >took that chance.
See my posting at: <http://groups.google.com/group/sci.electronics.design/msg/a4f97571c189673f> Some PC104 boards have isolated grounds. The idea is to prevent ground loops and keep the noise level down. It's also common in high end audio applications, where the audio and power grounds are seperate for the same reason.
> You are a liar. You have NOT "seen both".
No problem. Everyone lies, but that's ok because nobody listens. -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
On Sat, 25 Aug 2012 15:47:58 -0700, SoothSayer
<SaySooth@TheMonastery.org> wrote:

> The AT design sped. Covers Power supplies, cases, FCC Rule 15 >compliance, emissions standards... things like that.
ATX 2.2 spec: <http://www.formfactors.org/developer%5Cspecs%5Catx2_2.pdf> Nothing on grounding the PCB that I can find. FCC Part 15: <http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=83a8c3f5180c5c04dc038e32b563925f&rgn=div5&view=text&node=47:1.0.1.1.16&idno=47> etc... None of the voluminous specifications include anything on implimentation specifics such as grounding. The closest approximation would be Part 15.102, which covers "CPU boards and power supplies used in personal computers." <http://www.hallikainen.com/FccRules/2012/15/102/index.php> which is mostly about labeling and administrivia. -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
On Sat, 25 Aug 2012 18:19:02 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

>On Sat, 25 Aug 2012 17:57:38 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: > >>On Sat, 25 Aug 2012 17:44:16 -0700, John Larkin >><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >> >>>On Sat, 25 Aug 2012 15:09:16 -0700, Jim Thompson >>><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >>> >>>>On Sat, 25 Aug 2012 10:31:03 -0700, John Larkin >>>><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >>>> >>>>>On Sat, 25 Aug 2012 10:14:48 -0700, Jim Thompson >>>>><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >>>>> >>>>>>On Sat, 25 Aug 2012 10:03:49 -0700, John Larkin >>>>>><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >>>>>> >>>>>>>On Sat, 25 Aug 2012 09:40:54 -0700, Jim Thompson >>>>>>><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: >>>>>>> >>>>>>>>On Sat, 25 Aug 2012 09:34:54 -0700, John Larkin >>>>>>>><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote: >>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>>The mounting holes on PC motherboards: are they usually connected to >>>>>>>>>the PCB ground plane? >>>>>>>> >>>>>>>>depends. Are you wearing them like you should ?:-) >>>>>>>> >>>>>>>> ...Jim Thompson >>>>>>> >>>>>>>You never actually say anything with content any more. You don't even >>>>>>>discuss circuits in any intelligent way. You've become a useless old >>>>>>>hen. >>>>>> >>>>>>And your WORKING circuits are WHERE ?:-) >>>>>> >>>>>> ...Jim Thompson >>>>> >>>>>A few are here: >>>>> >>>>>http://www.highlandtechnology.com/index.shtml >>>>> >>>>> >>>>>Any your fast current source is where? You can't do it! >>>>> >>>>>I rather liked the mosfet-bipolar cascode with Ib correction, but you >>>>>didn't. What did you find wrong with it? I mean, aside from the fact >>>>>that I invented it. Are you claiming that this *won't* work? >>>>> >>>>>https://dl.dropbox.com/u/53724080/Circuits/Isrc_Ib_2.JPG >>>>> >>>>> >>>>>But I have a couple of better, cuter circuits by now. Show us your >>>>>approach, and then I'll post a couple more of mine. >>>>> >>>>>You never say anything substantive about electronics lately. You can't >>>>>invent circuits any more. Go back to sci.electronics.basics where >>>>>amateurs belong. >>>> >>>>Show some LTspice .ASC files that can be checked. Then people will >>>>believe your claims. >>>> >>> >>>That's silly. If you can't look at a circuit and understand it, and >>>decide how well it will work, and you need a simulator to do your >>>thinking for you, then you are an amateur. I wouldn't Spice anything >>>this simple. >>> >>>Good grief, you *don't* understand my circuit! >> >>You _do_ know how to make people snicker behind your back. >> >>Show us your final solution already... > >That's it. Anybody half competant should be able to write in the parts >values, immediately, without even needing a calculator. It's not worth >simulating because the low frequency behavior is obvious and the GHz >bits don't sim usefully because the transistor models aren't there. > >Why don't you design a fast current source? Because you can't! > >You *don't* understand my circuit!
WHERE did you SHOW a WORKING circuit ?? You didn't. I design sub-nanosecond stuff on-chip all the time, so shove your snarky crap up your ass. You're a shit "designer"... all NO-SHOW. ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
On Sat, 25 Aug 2012 20:03:43 -0400, "krw@att.bizzzzzzzzzzzz"
<krw@att.bizzzzzzzzzzzz> wrote:

> The FCC has their own ideas and even they don't >care what you do with the screws.
This isn't about screws, idiot. It is about industry wide and fully adopted and accepted circuit board design standards. You are a goddamned retard, Williams.
On Sat, 25 Aug 2012 18:24:02 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

> >However, way back in the pre-ATX style motherboard era, mounting was >done using plastic insulating spacers.
Except that a PROPER installation of ANY mobo into ANY case, even back then, involved at least ONE tie point of the MOBO to ground, and that was usually via a single hard stud/standoff. There NEVER was ANY proper mobo installations that was made full floating by the dumbass installer using plastic at every point. Even if a PhD did it, it was a failed assembly. It requires at least ONE tie to the chassis. That has ALWAYS been true. FOREVER! PERIOD!
On Sat, 25 Aug 2012 18:24:02 -0700, Jeff Liebermann <jeffl@cruzio.com>
wrote:

> The motherboard was still >grounded, but usually only with one brass standoff and screw.
Dumb fucks, every one of you. That was stated. Several times.