CTho

Re: Overclocking

Resistors. Deviation from nominal resistance is usually 15-20% at best on typical CMOS anyway, so a large enough temperature swing can change resistance values enough to cause timing problems. -- mattb @ 2006-09-11T03:13Z

In a CPU? Very few. In a DSP or GPU? There will be many in the DAC portion. Also remember that many interconnect resistances are not negligible in cutting-edge CMOS processes. Anyway, temperature will affect the MOSFET thermal voltage (look at your SPICE model equations), but the S-D current is a pretty weak function of thermal voltage. Of course, the lower the threshold of inversion voltage, the more temperature is likely to have a detrimental effect on the circuitry (and this is the effect you're probably seeing in your simulation). Actually what I took issue with is the spurious claim that MOSFETs slow down with temperature. Parasitic capacitance is the largest factor that affects MOSFET switching speed, and it is a VERY weak function of temperature. One reason for this is that, within a certain temperature range, carrier mobility in the channel with an increase in temperature.

So it's not so much that MOSFETs slow down with temperature, but they do become more susceptible to noise because of the increased thermal voltage. The instability exhibited by, for example, an overheated microprocessor is probably due to some gate(s) not having enough gate voltage applied to drive it into inversion at the current temperature. If you want to re-add the text with that correction, it's fine by me. -- mattb @ 2006-09-12T05:53Z

I don't mean to insult you, either, but it sounds to me like you've never actually designed semiconductor devices and are looking at SPICE simulations at a circuit level and guessing as to the cause of the effects you observed. You did not bother to explain WHY you think a MOSFET would slow down with increasing temperature, just that you don't believe my explanation. I don't expect you to take what I say as gospel, but if you're going to accuse me of misunderstanding then I at least ask that you attempt to offer an explanation of the appropriate effect rather than insisting that the transistor is going "slower" for unknown reasons. Failing that, I encourage you to review your device physics and basic quantum mechanics.

Let me explain again. The factor that most affects a gate's switching speed is obviously capacitance. However, the temperature dependance of capacitance in a MOS system is VERY weak (if you don't believe me, look up the mathematical models SPICE uses for temperature variation effects on capacitance). As a result, parameters like cutoff frequency and yes, gate switching speed, are not affected significantly by these small temperature swings. As I explained before, threshold voltage is probably the culprit here. To drive a MOS gate into strong inversion, the surface band bending of the semiconductor needs to be many times the thermal voltage. Taking the 100 K temperature swing you mentioned, it's not at all unfathomable that the threshold voltage of a MOSFET could decrease by a large factor. A quick calculation with some typical Si CMOS process numbers indicates that your temperature swing of 100 C could easily change a nMOSFET's threshold voltage by 35%, which could be non-trivial. I don't know for sure if this is a contributor to the instability seen in a mildly overheated VLSI system, but I suspect it plays a big role. It certainly plays a very significant role if you're comparing it to capacitance variation with temperature. Keep in mind also that a Si system begins to approach intrinsic carrier concentration at the temperatures you're talking about. The upper limit of Si device operation is usually put at around 450 K. Beyond that, thermally excited carriers begin to dominate doping-generated carriers and the device will simply stop functioning.

If you can think of or find a better physical explanation of the instability in an overheated microprocessor, please feel free to correct me. I don't claim to know much about digital VLSI, but understand that it's slightly offensive when you claim that I'm "misunderstanding" the device but you yourself cannot offer a better physical explanation of the effects you're observing. -- mattb @ 2006-09-13T05:01Z

Welcome and such

I wanted to drop you a line to welcome you to Wikipedia and encourage you to stick around. I hope that my reverting your edit and making you engage in this rather long dialogue won't sour your experience; I certainly mean no personal slight against you. Anyways, your experience is much needed on Wikipedia. The general state of computer architecture and digital electronics related articles is often pretty sad (just look at where CPU was not so long ago!), and the attention of a CmpE is just what many of them need. Even many of the larger articles need some serious attention; DRAM, Computer storage, Clock signal/Clock rate, etc come to mind. Right now I'm slowly working with some other people on revising the Computer article at Talk:Computer/Temp. Your input there would be much appreciated, since the current state of that article is medicore at best.

Anyway, welcome again, and thanks for being patient and helpful! -- mattb @ 2006-09-14T04:25Z

Biology Class

Hey, I thought you might find it interesting that my professor found your diffusion animation and used it within his lecture. Cheers! J.Steinbock 20:56, 17 November 2006 (UTC)

Cool, thanks for letting me know! --CTho 23:23, 17 November 2006 (UTC)

My bad

Sorry about mislabeling Image:Viking1Launch.jpg as a candidate for SVG conversion, I've got some macros for pasting various groups of templates and selected the wrong move-to-commons group without noticing it in this case. I'm usually a bit less of a klutz about that sort of thing. :) Bryan Derksen 06:00, 13 August 2007 (UTC)

No problem. --CTho 12:49, 13 August 2007 (UTC)

Rehnquist

You are not allowed to wipe out whole sections of an article with one click. You are welcome to provide alternative viewpoints (as long as everything is cited), but that section you tried to delete was based on a book by a conservative author who wrote that Rehnquist failed and that the Court would have to go, and is going, even more rightist to change all that. As it is, the fact remains that the conservatives failed on social issues, though Rehnquist did make some advances in terms of federalism. RafaelRGarcia (talk) 04:01, 9 September 2008 (UTC)

I removed the offensive two-word phrase. See how you like it now, but don't try to nuke the section. RafaelRGarcia (talk) 23:46, 9 September 2008 (UTC)

That version is fine. I have a tendency to repeat the words used in the sources I cite. "Impede" wasn't an incorrect word to use, as it was Rehnquist's goal from the moment he started on the Court, but "overturn" is fine. RafaelRGarcia (talk) 23:54, 9 September 2008 (UTC)

I know you like Rehnquist, so maybe you'll consider my "Good Article" nomination for him: http://en.wikipedia.org/w/index.php?title=Talk:William_Rehnquist/GA1&action=edit&editintro=Template:GAN/editintro&preload=Template:GAN/preload . RafaelRGarcia (talk) 14:24, 11 September 2008 (UTC)

Decollate snail

Sorry it took 1 1/2 years to get back to you! That really is a snail's pace! Anyway, yes, I think your photographs are indeed of that species. Where were they taken? They need cropping down a bit, but I like number 2 and number 4 in your series, that is, if you are still around and want to upload them. Many thanks, Invertzoo (talk) 22:01, 24 October 2008 (UTC)

Thanks so much for the excellent images! Invertzoo (talk) 13:01, 30 October 2008 (UTC)

Pittsburgh event for Wikipedia's tenth anniversary

Hi! Since you have a connection to Pittsburgh, I wanted to invite you to the Wikipedia Tenth Anniversary celebrations we're having in Pittsburgh on Saturday, January 15. During the daytime, we're going to be having a photo contribution drive where anyone can bring in their digital photos or prints and Wikipedians will teach people how to upload them and add them to articles, and maybe introduction to Wikipedia workshops as well. Then in the evening, we'll have fun at the Carson City Saloon. There will be free Wikipedia t-shirts and other goodies, as well. See the Pittsburgh meetup page for more details. I hope to see you there!--ragesoss (talk) 15:46, 1 January 2011 (UTC)

Teaching with Wikipedia Workshop at CMU (Aug 15)

Since you are one of the editors in the Category:Wikipedians by alma mater: Carnegie Mellon University, I'd like to invite you to the Teaching with Wikipedia Workshop that will take place at CMU on Aug 15 (this workshop is open to general public, and is a joint imitative of CMU and Pitt). There will be another workshop held at Pitt in the Fall as well. It will cover how to include Wikipedia in one's course (WP:SUP) and also how to become a Wikipedia:Campus Ambassadors. Pennsylvania has currently only one ambassador (myself) and it would be great if we could recruit at least several more. Ambassadors help course instructors, showing them how Wikipedia works, and interact with students. Many current ambassadors come from the body of students, faculty and university staff; it is a fun adventure, and adds to one resume/CV, to boot :) If it sounds interesting, feel free to ask me any questions, or to come to the workshop.--_{Piotr Konieczny aka Prokonsul Piotrus| talk} 20:08, 9 August 2011 (UTC)

File:Anthraxmailflow.svg listed for deletion

A file that you uploaded or altered, File:Anthraxmailflow.svg, has been listed at Wikipedia:Files for deletion. Please see the discussion to see why this is (you may have to search for the title of the image to find its entry), if you are interested in it not being deleted. Thank you. Cloudbound (talk) 21:15, 20 April 2012 (UTC)

ArbCom elections are now open!

Hi,
You appear to be eligible to vote in the current Arbitration Committee election. The Arbitration Committee is the panel of editors responsible for conducting the Wikipedia arbitration process. It has the authority to enact binding solutions for disputes between editors, primarily related to serious behavioural issues that the community has been unable to resolve. This includes the ability to impose site bans, topic bans, editing restrictions, and other measures needed to maintain our editing environment. The arbitration policy describes the Committee's roles and responsibilities in greater detail. If you wish to participate, you are welcome to review the candidates' statements and submit your choices on the voting page. For the Election committee, MediaWiki message delivery (talk) 13:38, 23 November 2015 (UTC)