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  • ICMP Redirect Theory VS. Application

    - by joeqwerty
    I'm trying to watch ICMP redirects in a lab using Cisco Packet Tracer (version 5.3.2) and I'm not seeing them, which leads me to believe that either my lab configuration isn't correct or my understanding of ICMP redirects isn't correct or that Packet Tracer doesn't support/use ICMP redirects. Here's what I believe to be true regarding ICMP redirects: Routers send ICMP redirects when all of these conditions are met: The interface on which the packet comes into the router is the same interface on which the packet gets routed out. The subnet or network of the source IP address is on the same subnet or network of the next-hop IP address of the routed packet. The datagram is not source-routed. The router kernel is configured to send redirects. I have the lab set up in Cisco Packet Tracer as displayed in the image and would expect to see an ICMP redirect from Router1 when pinging from PC1 to PC3. I'm not seeing the ICMP redirect and it looks like Router1 is actually routing all of the packets via Router2. I have IP ICMP debugging enabled on Router1 (and Router2) and I'm not seeing any ICMP redirect activity in either console. I'm also not seeing a route to the PC3 network in the routing table on PC1, which I think confirms that the ICMP redirect is not occurring. I'm using only static routing on Routers 1 and 2. Is my understanding of ICMP redirects incorrect, or is there a problem with my lab configuration or does Packet Tracer not support/use ICMP redirects?

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  • DNA and Quantum computing

    - by Jacques
    I recently(A couple of weeks ago) read an article about the future of processing and how quantum-processors and DNA-processors(DNA-computing) are the future competitors of computing since both will completely outperform the computers of this era. In terms of processing speeds, what do we expect from these two different processing techniques ? Personally I believe that DNA-processing will be a major step towards AI. For labs and office work I think quantum-processing which will be more logical. I'm quite excited that i'm still so young - to see what the future of technology holds! Then again my parents will soon find out what the after-life holds... just as bloody exciting, if not more..

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  • Do you know what is a DevOps Project?

    - by Gopinath
    Yesterday I wrote about OpenStack project, an open source cloud computing stack that lets you build Cloud Computing environments. While reading more on this topic I stumbled about a new type of projects called DevOps projects.  OpenStack is all set to become the first DevOps project, reports Forbes …the way OpenStack is applying the open source model to creating cloud infrastructure, the open source model is on the verge of being extended so that the collaboration and design process will include software, hardware, and networking in the data center as well as operational processes. In modern development, the idea of designing software, data center, and operations using one integrated team is called DevOps.

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  • Developing a Support Plan for Cloud Applications

    - by BuckWoody
    Last week I blogged about developing a High-Availability plan. The specifics of a given plan aren't as simple as "Step 1, then Step 2" because in a hybrid environment (which most of us have) the situation changes the requirements. There are those that look for simple "template" solutions, but unless you settle on a single vendor and a single way of doing things, that's not really viable. The same holds true for support. As I've mentioned before, I'm not fond of the term "cloud", and would rather use the tem "Distributed Computing". That being said, more people understand the former, so I'll just use that for now. What I mean by Distributed Computing is leveraging another system or setup to perform all or some of a computing function. If this definition holds true, then you're essentially creating a partnership with a vendor to run some of your IT - whether that be IaaS, PaaS or SaaS, or more often, a mix. In your on-premises systems, you're the first and sometimes only line of support. That changes when you bring in a Cloud vendor. For Windows Azure, we have plans for support that you can pay for if you like. http://www.windowsazure.com/en-us/support/plans/ You're not off the hook entirely, however. You still need to create a plan to support your users in their applications, especially for the parts you control. The last thing they want to hear is "That's vendor X's problem - you'll have to call them." I find that this is often the last thing the architects think about in a solution. It's fine to put off the support question prior to deployment, but I would hold off on calling it "production" until you have that plan in place. There are lots of examples, like this one: http://www.va-interactive.com/inbusiness/editorial/sales/ibt/customer.html some of which are technology-specific. Once again, this is an "it depends" kind of approach. While it would be nice if there was just something in a box we could buy, it just doesn't work that way in a hybrid system. You have to know your options and apply them appropriately.

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  • Developing a Support Plan for Cloud Applications

    - by BuckWoody
    Last week I blogged about developing a High-Availability plan. The specifics of a given plan aren't as simple as "Step 1, then Step 2" because in a hybrid environment (which most of us have) the situation changes the requirements. There are those that look for simple "template" solutions, but unless you settle on a single vendor and a single way of doing things, that's not really viable. The same holds true for support. As I've mentioned before, I'm not fond of the term "cloud", and would rather use the tem "Distributed Computing". That being said, more people understand the former, so I'll just use that for now. What I mean by Distributed Computing is leveraging another system or setup to perform all or some of a computing function. If this definition holds true, then you're essentially creating a partnership with a vendor to run some of your IT - whether that be IaaS, PaaS or SaaS, or more often, a mix. In your on-premises systems, you're the first and sometimes only line of support. That changes when you bring in a Cloud vendor. For Windows Azure, we have plans for support that you can pay for if you like. http://www.windowsazure.com/en-us/support/plans/ You're not off the hook entirely, however. You still need to create a plan to support your users in their applications, especially for the parts you control. The last thing they want to hear is "That's vendor X's problem - you'll have to call them." I find that this is often the last thing the architects think about in a solution. It's fine to put off the support question prior to deployment, but I would hold off on calling it "production" until you have that plan in place. There are lots of examples, like this one: http://www.va-interactive.com/inbusiness/editorial/sales/ibt/customer.html some of which are technology-specific. Once again, this is an "it depends" kind of approach. While it would be nice if there was just something in a box we could buy, it just doesn't work that way in a hybrid system. You have to know your options and apply them appropriately.

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  • Is there the equivalent of cloud computing for modems?

    - by morpheous
    I asked this question on SF, and someone recommended that I ask it here - (I don't think I have enough points to move a question from SF to SO - and in any case, I don't know how to do it - so here is the question again): I am interested in the concept of PAAS (platform as a service). However, all talk about SAAS/PAAS seems to focus on only the computer itself - not its peripherals. Is it possible to 'outsource' modems as a resource - so that an app running remotely can pump data to a modem in the cloud? As a bit of background to the question, a group of us are thinking of starting a company that offers similar services to companies like twilio etc - but I want to 'outsource' both the computing hardware (thats PAAS - the easy bit) and the modems (thats what I cant seem to find any info on). Does anyone know if modems can be bundled as part of a PAAS service? - alternatively, is there a way that an application running on one computer can communicate (i.e. pump data) to a remote modem residing on another machine?. I assume I can come up with some protocol over UDP or TCP - but there is no point reinventing the wheel - if such a protocol like that already exists (or if it some open source software allows one to do this). Any suggestions on how to solve this problem?

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  • What will we use Theory Attribute for ?

    - by Sandbox
    I discovered [Theory] and [Datapoint] attributes in NUnit. I am not very sure about how should I use these. I think they can be used for data-driven testing and this has got me interested. There aren't many resources available on the same. Can someone explain to me how to use them or point me to resources? Thanks.

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  • Point me to info about constructing filters (of lists)

    - by jah
    I would like some pointers to information which would help me understand how to go about providing the ability to filter a list of entities by their attributes as well as by attributes of related entities. As an example, imagine a web app which provides order management of some kind. Orders and related entities are stored in a relational database. And imagine that the app has an interface which lists the orders. The problem is: how does one allow the list to be filtered by, for example:- order number (an attribute) line item name (an attribute of a n-n related entity) some text in an administrative note related to the order (text found in an attribute of a 1-1 related entity) I'm trying to discover whether there is something like a standard, efficient way to construct the queries and the filtering form; or some possible strategies; or any theory on the topic; or some example code. My google foo fails me.

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  • Setting up MongoDB in High Performance Computing LSF linux cluster

    - by Dnaiel
    I am trying to run mongo in a LSF cluster computing environment where I have no admin control. Our sysadmin installed mongodb, but it is not running. Any ideas on what should I ask the server admin to do for it to run? Or if I could run it locally? [node1382]allelix> mongod --dbpath /users/dnaiel/ma/mongodb/ Tue Oct 2 21:33:48 [initandlisten] MongoDB starting : pid=22436 port=27017 dbpath=/seq/epigenome01/allelix/ma/mongodb/ 64-bit host=node1382 Tue Oct 2 21:33:48 [initandlisten] Tue Oct 2 21:33:48 [initandlisten] ** WARNING: You are running on a NUMA machine. Tue Oct 2 21:33:48 [initandlisten] ** We suggest launching mongod like this to avoid performance problems: Tue Oct 2 21:33:48 [initandlisten] ** numactl --interleave=all mongod [other options] Tue Oct 2 21:33:48 [initandlisten] Tue Oct 2 21:33:48 [initandlisten] db version v2.2.0, pdfile version 4.5 Tue Oct 2 21:33:48 [initandlisten] git version: f5e83eae9cfbec7fb7a071321928f00d1b0c5207 Tue Oct 2 21:33:48 [initandlisten] build info: Linux ip-10-2-29-40 2.6.21.7-2.ec2.v1.2.fc8xen #1 SMP Fri Nov 20 17:48:28 EST 2009 x86_64 BOOST_LIB_VERSION=1_49 Tue Oct 2 21:33:48 [initandlisten] options: { dbpath: "/users/dnaiel/ma/mongodb/" } Tue Oct 2 21:33:48 [initandlisten] journal dir=users/dnaiel/ma/mongodb/journal Tue Oct 2 21:33:48 [initandlisten] recover begin Tue Oct 2 21:33:48 [initandlisten] info no lsn file in journal/ directory Tue Oct 2 21:33:48 [initandlisten] recover lsn: 0 Tue Oct 2 21:33:48 [initandlisten] recover /seq/epigenome01/allelix/ma/mongodb/journal/j._0 Tue Oct 2 21:33:48 [initandlisten] recover cleaning up Tue Oct 2 21:33:48 [initandlisten] removeJournalFiles Tue Oct 2 21:33:48 [initandlisten] recover done Tue Oct 2 21:33:48 [websvr] admin web console waiting for connections on port 28017 Tue Oct 2 21:33:48 [initandlisten] waiting for connections on port 27017 It basically waits forever and cannot start mongodb. These servers are not webservers but they do have network access, it's a cloud computing LSF environment system. Any advice would be welcome, thanks in advance.

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  • Translation of clustering problem to graph theory language

    - by honk
    I have a rectangular planar grid, with each cell assigned some integer weight. I am looking for an algorithm to identify clusters of 3 to 6 adjacent cells with higher-than-average weight. These blobs should have approximately circular shape. For my case the average weight of the cells not containing a cluster is around 6, and that for cells containing a cluster is around 6+4, i.e. there is a "background weight" somewhere around 6. The weights fluctuate with a Poisson statistic. For small background greedy or seeded algorithms perform pretty well, but this breaks down if my cluster cells have weights close to fluctuations in the background. Also, I cannot do a brute-force search looping through all possible setups because my grid is large (something like 1000x1000). I have the impression there might exist ways to tackle this in graph theory. I heard of vertex-covers and cliques, but am not sure how to best translate my problem into their language.

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  • box stacking in graph theory

    - by mozhdeh
    Please help me find a good solution for this problem. We have n boxes with 3 dimensions. We can orient them and we want to put them on top of another to have a maximun height. We can put a box on top of an other box, if 2 dimensions (width and lenght) are lower than the dimensions of the box below. For exapmle we have 3 dimensions w*D*h, we can show it in to (h*d,d*h,w*d,d*W,h*w,w*h) please help me to solve it in graph theory.

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  • Theory of computation - Using the pumping lemma for context free languages

    - by Tony
    I'm reviewing my notes for my course on theory of computation and I'm having trouble understanding how to complete a certain proof. Here is the question: A = {0^n 1^m 0^n | n>=1, m>=1} Prove that A is not regular. It's pretty obvious that the pumping lemma has to be used for this. So, we have |vy| = 1 |vxy| <= p (p being the pumping length, = 1) uv^ixy^iz exists in A for all i = 0 Trying to think of the correct string to choose seems a bit iffy for this. I was thinking 0^p 1^q 0^p, but I don't know if I can obscurely make a q, and since there is no bound on u, this could make things unruly.. So, how would one go about this?

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  • Theory of computation - Using the pumping lemma for CFLs

    - by Tony
    I'm reviewing my notes for my course on theory of computation and I'm having trouble understanding how to complete a certain proof. Here is the question: A = {0^n 1^m 0^n | n>=1, m>=1} Prove that A is not regular. It's pretty obvious that the pumping lemma has to be used for this. So, we have |vy| = 1 |vxy| <= p (p being the pumping length, = 1) uv^ixy^iz exists in A for all i = 0 Trying to think of the correct string to choose seems a bit iffy for this. I was thinking 0^p 1^q 0^p, but I don't know if I can obscurely make a q, and since there is no bound on u, this could make things unruly.. So, how would one go about this?

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  • Real life usage of the projective plane theory

    - by Elazar Leibovich
    I'm learning about the theory of the projective plane. Very generally speaking, it is an extension of the plane, which includes additional points which are defined as the intersection points of two parallel lines. In the projective plane, every two lines have an interesection point. Whether they're parallel or not. Every point in the projective plane can be represented by three numbers (you actually need less than that, but nevemind now). Is there any real life application which uses the projective plane? I can think that, for instance, a software which needs to find the intersections of a line, can benefit from always having an intersection point which might lead to simpler code, but is it really used?

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  • A compiler for automata theory

    - by saadtaame
    I'm designing a programming language for automata theory. My goal is to allow programmers to use machines (DFA, NFA, etc...) as units in expressions. I'm confused whether the language should be compiled, interpreted, or jit-compiled! My intuition is that compilation is a good choice, for some operations might take too much time (converting NFA's to equivalent DFA's can be expensive). Translating to x86 seems good. There is one issue however: I want the user to be able to plot machines. Any ideas?

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  • How can I make sense of the word "Functor" from a semantic standpoint?

    - by guillaume31
    When facing new programming jargon words, I first try to reason about them from an semantic and etymological standpoint when possible (that is, when they aren't obscure acronyms). For instance, you can get the beginning of a hint of what things like Polymorphism or even Monad are about with the help of a little Greek/Latin. At the very least, once you've learned the concept, the word itself appears to go along with it well. I guess that's part of why we name things names, to make mental representations and associations more fluent. I found Functor to be a tougher nut to crack. Not so much the C++ meaning -- an object that acts (-or) as a function (funct-), but the various functional meanings (in ML, Haskell) definitely left me puzzled. From the (mathematics) Functor Wikipedia article, it seems the word was borrowed from linguistics. I think I get what a "function word" or "functor" means in that context - a word that "makes function" as opposed to a word that "makes sense". But I can't really relate that to the notion of Functor in category theory, let alone functional programming. I imagined a Functor to be something that creates functions, or behaves like a function, or short for "functional constructor", but none of those seems to fit... How do experienced functional programmers reason about this ? Do they just need any label to put in front of a concept and be fine with it ? Generally speaking, isn't it partly why advanced functional programming is hard to grasp for mere mortals compared to, say, OO -- very abstract in that you can't relate it to anything familiar ? Note that I don't need a definition of Functor, only an explanation that would allow me to relate it to something more tangible, if there is any.

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  • Minimizing data sent over a webservice call on expensive connection

    - by aceinthehole
    I am working on a system that has many remote laptops all connected to the internet through cellular data connections. The application will synchronize periodically to a central database. The problem is, due to factors outside our control, the cost to move data across the cellular networks are spectacularly expensive. Currently the we are sending a compressed XML file across the wire where it is being processed and various things are done with (mainly stuffing it into a database). My first couple of thoughts were to convert that XML doc to json, just prior to transmission and convert back to XML just after receipt on the other end, and get some extra compression for free without changing much. Another thought was to test various other compression algorithms to determine the smallest one possible. Although, I am not entirely sure how much difference json vs xml would make once it is compressed. I thought that their must be resources available that address this problem from an information theory perspective. Does anyone know of any such resources or suggestions on what direction to go in. This developed on the MS .net stack on windows for reference.

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  • Japanese Multiplication simulation - is a program actually capable of improving calculation speed?

    - by jt0dd
    On SuperUser, I asked a (possibly silly) question about processors using mathematical shortcuts and would like to have a look at the possibility at the software application of that concept. I'd like to write a simulation of Japanese Multiplication to get benchmarks on large calculations utilizing the shortcut vs traditional CPU multiplication. I'm curious as to whether it makes sense to try this. My Question: I'd like to know whether or not a software math shortcut, as described above is actually a shortcut at all. This is a question of programming concept. By utilizing the simulation of Japanese Multiplication, is a program actually capable of improving calculation speed? Or am I doomed from the start? The answer to this question isn't required to determine whether or not the experiment will succeed, but rather whether or not it's logically possible for such a thing to occur in any program, using this concept as an example. My theory is that since addition is computed faster than multiplication, a simulation of Japanese multiplication may actually allow a program to multiply (large) numbers faster than the CPU arithmetic unit can. I think this would be a very interesting finding, if it proves to be true. If, in the multiplication of numbers of any immense size, the shortcut were to calculate the result via less instructions (or faster) than traditional ALU multiplication, I would consider the experiment a success.

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  • EL FUTURO DEL CLOUD, A DEBATE EN EL XX CONGRESO NACIONAL DE USUARIOS ORACLE

    - by comunicacion-es_es(at)oracle.com
    Normal 0 21 false false false ES X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0cm 5.4pt 0cm 5.4pt; mso-para-margin-top:0cm; mso-para-margin-right:0cm; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0cm; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin;} ¡Vuelta a un mini Oracle OpenWorld! La Comunidad de Usuarios de Oracle celebrará en Madrid los próximos 16 y 17 de marzo su XX Congreso Nacional, donde estarán representadas TODAS las áreas de Oracle (aplicaciones, tecnología, hardware y canal). Bajo el lema "Agilidad, innovación y optimización del negocio", contaremos con prestigiosos ponentes internacionales como Massimo Pezzini, vicepresidente de Gartner; Rex Wang, experto en Cloud Computing y vicepresidente de marketing de producto de Oracle; y Janny Ekelson, director de aplicaciones y arquitectura FedEx Express Europa. A parte de los más de 15 casos de éxito, en las más de 40 presentaciones programadas, el Cloud Computing será uno de los temas estrella junto a la estrategia en hardware de Oracle tras la adquisición de Sun. ¡Os esperamos!

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  • Array Multiplication and Division

    - by Narfanator
    I came across a question that (eventually) landed me wondering about array arithmetic. I'm thinking specifically in Ruby, but I think the concepts are language independent. So, addition and subtraction are defined, in Ruby, as such: [1,6,8,3,6] + [5,6,7] == [1,6,8,3,6,5,6,7] # All the elements of the first, then all the elements of the second [1,6,8,3,6] - [5,6,7] == [1,8,3] # From the first, remove anything found in the second and array * scalar is defined: [1,2,3] * 2 == [1,2,3,1,2,3] But What, conceptually, should the following be? None of these are (as far as I can find) defined: Array x Array: [1,2,3] * [1,2,3] #=> ? Array / Scalar: [1,2,3,4,5] / 2 #=> ? Array / Scalar: [1,2,3,4,5] % 2 #=> ? Array / Array: [1,2,3,4,5] / [1,2] #=> ? Array / Array: [1,2,3,4,5] % [1,2] #=> ? I've found some mathematical descriptions of these operations for set theory, but I couldn't really follow them, and sets don't have duplicates (arrays do). Edit: Note, I do not mean vector (matrix) arithmetic, which is completely defined. Edit2: If this is the wrong stack exchange, tell me which is the right one and I'll move it. Edit 3: Add mod operators to the list. Edit 4: I figure array / scalar is derivable from array * scalar: a * b = c => a = b / c [1,2,3] * 3 = [1,2,3]+[1,2,3]+[1,2,3] = [1,2,3,1,2,3,1,2,3] => [1,2,3] = [1,2,3,1,2,3,1,2,3] / 3 Which, given that programmer's division ignore the remained and has modulus: [1,2,3,4,5] / 2 = [[1,2], [3,4]] [1,2,3,4,5] % 2 = [5] Except that these are pretty clearly non-reversible operations (not that modulus ever is), which is non-ideal. Edit: I asked a question over on Math that led me to Multisets. I think maybe extensible arrays are "multisets", but I'm not sure yet.

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  • Java NIO (Netty): How does Encryption or GZIPping work in theory (with filters)

    - by Tom
    Hello Experts, i would be very thankfull if you can explain to me, how in theory the "Interceptor/Filter" Pattern in ByteStreams (over Sockets/Channels) work (in Asynchronous IO with netty) in regard to encryption or compression of data. Given I have a Filter that does GZIPPING. How is this internally implemented? Does the Filter "collect" so many bytes form the channel, that this is a usefull number of bytes that can then be en/decoded? What is in general the minimal "blocksize(data to encode/decode in a chunk)" of socket based gzipping? Does this "blocksize" have to be negotiated in advance between server and client? What happens if the client does not send enough data to "fill" the blocksize (due to a network conquestion) but does not close the connection. Does this mean the other side will simply wait until it gets enough bytes to decode or until a timeout occoures...How is the Filter pattern the applied? The compression filter will de/compress the blocksize of bytes and then store them again in the same buffer would (in the case of netty) i normally be using the ChannelHanlderContext to pass the de/encoded data to the next filter?... Any explanations/links/tutorials (for beginners;-) will be very much appreciated to help me understand how for example encryption/compressing are implemented in socket based communication with filters/interceptor pattern. thank you very much tom

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  • GPU Computing - # of GPUs supported

    - by TehTypoKing
    I currently have a desktop with 6 GPUs ( 3x HD 5970s ) in non-crossfire mode. Unfortunately, it seems that Windows 7 64bit only supports up to 4 GPUs. I have not been able to find a reliable source to deny or confirm this. If windows 7 has this limitation, is there a Linux flavor that supports more than 4 GPUs? In-case you are wondering, this is not for gaming but high-speed single precision computing. With this current setup ( if I can find 6gpu support ) I am looking to reach 13.8 Teraflops. Also, my motherboard does support 3 16x pci-xpress gen2 slots... and I have a 1500w powersupply plugged into a 20amp outlet. Windows is able to detect all 6 cores.. although, 2 of which displays the warning "Drivers failed to load". To recap: - Can windows support 6 GPUs? - If not, does Linux? Thank you.

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