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The speed of the network card and the real speed of the internet

Jozef2038 14961 19
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Is a 100 Mb/s network card the limit for a 120 Mb/s internet connection, and why do speed tests show only 94–95 Mb/s?

A 100 Mb/s Ethernet link normally tops out at about 94–95 Mb/s in real speed tests, so that result is expected for a 100 Mb/s negotiation, but in your case the actual bottleneck was the cable, not the gigabit card [#16930541][#16930562][#16937741] The Intel 82579LM is a 1 Gb/s adapter, so if it falls back to 100 Mb/s, check whether 1 Gb/s is enabled in the adapter settings and whether the link is really negotiating at 1 Gbit [#16934687][#16932979] In the thread, replacing the old cable immediately changed the link to 1 Gb/s and raised the speed test from about 95 Mb/s to around 130–140 Mb/s [#16937741] A damaged or poor-quality cable can force the connection down to 100 Mb/s even when the PC and router support gigabit [#16930666][#16937741]
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  • #1 16930528
    Jozef2038
    Level 8  
    Posts: 25
    Rate: 1
    Hello I have a question. I was looking for a bit of google but I did not find anything specific. My question is, I have an allegedly 120mb / s Internet connection. I have a LAN connection and I write that the connection speed is 100Mb / s. Is this the maximum speed that will flow through my card? I will add that on speedtests I have 94-95mbps. greetings
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    #2 16930538
    Vytautas_YT
    Level 30  
    Posts: 1425
    Help: 128
    Rate: 297
    Well, then 94-95 is probably the limit of your card's ability, buy yourself the simplest card working in 1Gbps.
    One more thing, what are you using this computer for? To any router / modem? Toss a model.
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    #3 16930541
    sanfran
    Network and Internet specialist  
    Posts: 9789
    Help: 953
    Rate: 2945
    Yes, it's the maximum speed.
    The reason why Speedtest shows 94-95 is that when the data wants to exceed 100mbps, the packets are queued and in the case of exceeding the queue size simply thrown away.
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    #4 16930551
    JacekCz
    Level 42  
    Posts: 8670
    Help: 760
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    post is in the "Wifi" group.
    If you're actually talking about a copper cable, speed is a derivative
    a) both sides of the link, i.e. the network card and switch (on the principle of the "lowest common denominator"). Limited 100mbit network cards are from the age of dinosaurs. The fairy tells you that the switch limits you.
    b) cabling quality.
    c) settings
    In the wiring of dubious quality, I often limit the speed to 100mbit, I prefer to have a stable 100, than 1Gb with humor and spells.


    EDIT, of course, still words from the borderline of marketing providers, the transmission has mark-ups, firstly, secondly, written in papers, etc ... kilo / mega / giga in binary terms is 1024, 1048576, 1073741824, in decimal 1000, 10000000, guess which use marketers
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    #5 16930562
    wesoł2008
    Level 11  
    Posts: 12
    Help: 1
    Rate: 5
    you can not confuse megabits with mega bytes. Theoretically, the speed of the card should almost always exceed the speed of the net. On the test it will also not work out and how else because someone set a limiter for you - like the 120Mb. Now 120Mb it is equal to 15 MB in megabytes (mega bytes or in what we operate on a hard disk on a CD or pens.
  • #6 16930652
    Jozef2038
    Level 8  
    Posts: 25
    Rate: 1
    Ok, thank you for the numerous explanation of the topic. And is someone able to give me the possible reason why my card works in 100Mbps mode? I have an Intel (R) 82579LM Gigabit and I write on the Intel website that Data Rate Per Port 1 Gbps. So from where 100mb / s.

    I have an optical fiber that goes to a fiber optic center. There are 4 LAN-type inputs. The fitter said that there are two cable TV and 2 internet. So one thing goes to the PC and the other to the wifi router 3 for television and one is free. I will add that it does not matter if the router turned on and the television works, the result is always the same 94-95mbps

    I will add that the cable going from the control panel to my pc on which the tests are carried out is about 5 meters long and has already been in one place, the insulation is peeled off, no copper is used, copper is unmachined, only external insulation of wires is used) .
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    #7 16930666
    Ricoh_220

    Level 38  
    Posts: 3714
    Help: 464
    Rate: 750
    Which cable router does the computer not have 5 categories?
    I had at my place so that the 5c dropped the transfer to 100mb I exchanged and I have peace.
    Start with the cable without downloading the data I have 1Gb speed,
    Company Account:
    Zakład techniki biurowej"Kserograf" .Serwis kserokopiarek i urzdzeń marki ricoh
    Bronowicka 73, Kraków, 30-091 | Tel.: 603XXXXXX (Show) | Company Website: https://kserograf.e.pl
  • #8 16930674
    Jozef2038
    Level 8  
    Posts: 25
    Rate: 1
    Ricoh_220 wrote:
    Which cable router does the computer not have 5 categories?


    The cable that goes from the fiber optic center to my pc. The wifi router has a connection with the fiber optic center with a separate cable. I will add that I do not have a computer from the period of windows XP. It is a computer with intel i5, 8gb ramu, and I have an annual disk that reaches in hdd tune over 100mb / s so there is no way that the computer blocks me
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    #9 16930679
    Ricoh_220

    Level 38  
    Posts: 3714
    Help: 464
    Rate: 750
    I am writing about the cable you described as damaged.
    As you highlight the connection and everything ok, I have no right to be 100mb
    Company Account:
    Zakład techniki biurowej"Kserograf" .Serwis kserokopiarek i urzdzeń marki ricoh
    Bronowicka 73, Kraków, 30-091 | Tel.: 603XXXXXX (Show) | Company Website: https://kserograf.e.pl
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  • #10 16930685
    Jozef2038
    Level 8  
    Posts: 25
    Rate: 1
    Ricoh_220 wrote:
    Which cable router does the computer not have 5 categories?
    I had at my place so that the 5c dropped the transfer to 100mb I exchanged and I have peace.
    Start with the cable without downloading the data I have 1Gb speed,



    Ok, I'll try tomorrow, move the pc to the room where I have fiber optic and connect the pc with a short cable that I once got along with the router and see if it will actually be 1gbps
  • #11 16932184
    Nagus
    Level 27  
    Posts: 757
    Help: 99
    Rate: 97
    Specify the terms "fiber optic center", "wifi router" - device models. You should start with this.
  • #12 16932979
    alvaro99
    Level 22  
    Posts: 843
    Help: 34
    Rate: 47
    View the router or the options on the network adapter if you have the 1 Gbit option enabled.
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    #13 16934687
    Vytautas_YT
    Level 30  
    Posts: 1425
    Help: 128
    Rate: 297
    Connect to the cable you have connected the router and compare. Maybe you have 1Gbps disabled in the network adapter configuration. Well, what is this "fiber center", what exactly do you mean? Because you do not live in a telecommunication closet :D
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  • #14 16937741
    Jozef2038
    Level 8  
    Posts: 25
    Rate: 1
    Subject resolved. Ricoh_220 very well diagnosed the problem. After connecting with another cable, the test starts at 400Mbps :O but it drops to 130-140 and that's the speed. On an old cable, each result is 95Mbps. And the most important thing on the new cable is 1Gb / s
    http://www.speedtest.net/my-result/6938375803
    Score on the old cable

    The result on the new one

    http://www.speedtest.net/my-result/6938333825


    One more question about which cable to invest. Screened? And what type
  • #15 16937759
    JacekCz
    Level 42  
    Posts: 8670
    Help: 760
    Rate: 1460
    Jozef2038 wrote:

    One more question about which cable to invest. Screened? And what type


    You say "invest" ...
    you have a more important question: rigid cable terminated with sockets, or "holy sacred" with crimping plugs?
  • #16 16937785
    Jozef2038
    Level 8  
    Posts: 25
    Rate: 1
    JacekCz wrote:
    Jozef2038 wrote:

    One more question about which cable to invest. Screened? And what type


    You say "invest" ...
    you have a more important question: rigid cable terminated with sockets, or "holy sacred" with crimping plugs?


    Of course, it's a good cable for a good company, not crimping the ends


    / EDIT

    Which one will be better CAT 5E or CAT 6? Or maybe another one
  • #17 16937802
    JacekCz
    Level 42  
    Posts: 8670
    Help: 760
    Rate: 1460
    Jozef2038 wrote:
    JacekCz wrote:
    Jozef2038 wrote:

    One more question about which cable to invest. Screened? And what type


    You say "invest" ...
    you have a more important question: rigid cable terminated with sockets, or "holy sacred" with crimping plugs?


    Of course, it's a good cable for a good company, not crimping the ends


    In the previous post you write that it is about the next room. A slight inaccuracy.
    Cables on the market have up to 15m, but in the past respected standards spoke about max 5m flexible end-cable (ie recognized network companies should not have more)
  • #18 16937806
    Jozef2038
    Level 8  
    Posts: 25
    Rate: 1
    JacekCz wrote:
    Jozef2038 wrote:
    JacekCz wrote:
    Jozef2038 wrote:

    One more question about which cable to invest. Screened? And what type


    You say "invest" ...
    you have a more important question: rigid cable terminated with sockets, or "holy sacred" with crimping plugs?


    Of course, it's a good cable for a good company, not crimping the ends


    In the previous post you write that it is about the next room. A slight inaccuracy.
    Cables on the market have up to 15m, but in the past respected standards spoke about max 5m flexible end-cable (ie recognized network companies should not have more)


    I need 10 meters and it will be with the supply.

    I'm thinking about it
    http://allegro.pl/kabel-sieciowy-lan-pro-ethernet-rj45-utp-cat6-10m-i5970612258.html
  • #19 16937818
    JacekCz
    Level 42  
    Posts: 8670
    Help: 760
    Rate: 1460
    Jozef2038 wrote:
    I wonder about this ...


    Is it just a "known company" ... just a typical cable on the market.
    How will you walk the wall?
  • #20 16937871
    Jozef2038
    Level 8  
    Posts: 25
    Rate: 1
    The topic for closure got all the necessary information.

    Thank you again for Ricoh_220 for solving the problem
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Topic summary

✨ The discussion revolves around the discrepancy between the user's 120 Mbps internet connection and the 100 Mbps speed reported by their LAN connection, which is limited by the network card's capabilities. Users suggest that the Intel 82579LM Gigabit network card should support speeds up to 1 Gbps, indicating that the issue may stem from the quality of the Ethernet cable or configuration settings. The user experiences consistent speed tests around 94-95 Mbps, which aligns with the limitations of their current setup. After testing with a new cable, speeds improved significantly, confirming that the original cable was likely damaged. Recommendations for cable types include CAT 5E and CAT 6, with a preference for high-quality, rigid cables over crimped options.
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FAQ

TL;DR: If your PC negotiates 100 Mb/s, real downloads cap near 94–95 Mb/s; “Yes, it’s the maximum speed.” [Elektroda, sanfran, post #16930541]

Why it matters: This FAQ helps home users diagnose why a gigabit-capable setup only delivers ~95 Mb/s and how to reach true 1 Gb/s.

Quick Facts

Why does my 120 Mb/s plan only hit ~95 Mb/s on speed tests?

Your PC is linking at Fast Ethernet (100 Mb/s). With protocol overhead, measured throughput lands near 94–95 Mb/s. “Yes, it’s the maximum speed.” To exceed ~95 Mb/s, the link must negotiate 1 Gb/s end‑to‑end (NIC, router/ONT, and cable). [Elektroda, sanfran, post #16930541]

How do I check and enable 1 Gbit on my Windows NIC?

Open Device Manager → Network adapters → your NIC → Advanced. Ensure Speed & Duplex is on Auto Negotiation or 1.0 Gbps Full Duplex. Also confirm your router/ONT LAN port supports 1 Gbit. If 1 Gbit is disabled anywhere, you’ll cap at 100 Mb/s. [Elektroda, alvaro99, post #16932979]

Can a bad Ethernet cable force 100 Mb/s instead of 1 Gb/s?

Yes. A damaged or marginal cable can drop a gigabit link to 100 Mb/s. Replacing the suspect cable restored a 1 Gb/s link, and tests jumped from 95 Mb/s to 130–140 Mb/s (initial burst ~400 Mb/s). [Elektroda, Jozef2038, post #16937741]

Which should I buy: Cat5e or Cat6 for a short home run?

Choose a quality, brand‑name cable and avoid sloppy terminations. The thread focuses on using good cable rather than crimped ends, not on marketing labels. Plan proper terminations for reliability. [Elektroda, JacekCz, post #16937759]

What exactly is the "fiber optic center" box from my ISP?

Provide the exact model labels. Helpers asked for device models because behavior varies by ONT/router. Knowing the model clarifies port speeds and service VLANs. [Elektroda, Nagus, post #16932184]

My speed test starts near 400 Mb/s then settles at 130–140 Mb/s—normal?

Short bursts can hit cached or TCP window peaks, then stabilize to the sustained rate. After fixing the cable, results stabilized near 130–140 Mb/s with an initial spike around 400 Mb/s. [Elektroda, Jozef2038, post #16937741]

Quick 3‑step: how do I diagnose a 100 Mb/s link on gigabit hardware?

  1. Bypass in‑wall runs: move the PC next to the ONT/router and use a known‑good short patch.
  2. Check NIC settings: set Auto or 1.0 Gbps Full Duplex.
  3. Swap the patch cable; if link LED or status jumps to 1 Gb/s, replace the old run. [Elektroda, Jozef2038, post #16930685]

What’s the difference between Mb/s and MB/s when comparing speeds?

ISPs quote megabits per second (Mb/s). File managers show megabytes per second (MB/s). Divide Mb/s by 8 to estimate MB/s. Example: 120 Mb/s ≈ 15 MB/s. Mixing units leads to confusion about expected download rates. [Elektroda, wesoł2008, post #16930562]

Can flaky cabling make gigabit unstable even if it negotiates 1 Gb/s?

Yes. Poor cabling can cause retransmissions and drops. Many prefer forcing 100 Mb/s on weak runs for stability over an unreliable 1 Gb/s link. “I prefer to have a stable 100.” [Elektroda, JacekCz, post #16930551]

Do TV set‑top services on other ports slow my PC’s internet?

Not in this case. The user saw the same ~95 Mb/s regardless of TV or router activity. The bottleneck was the Ethernet link and cabling, not the active TV ports. [Elektroda, Jozef2038, post #16930652]

Should I use shielded Ethernet for a 10 m room‑to‑room run?

Focus first on build quality and proper termination. One expert emphasized choosing rigid cable terminated in sockets over ad‑hoc crimped plugs for reliability. Good terminations beat questionable shielding in short runs. [Elektroda, JacekCz, post #16937759]

How long can patch cables be, and does length affect performance?

Patch leads are commonly sold up to about 15 m. Older guidance suggested around 5 m for flexible end‑cables in structured cabling. Excessive length and poor quality can impair gigabit stability. [Elektroda, JacekCz, post #16937802]

What if my Intel 82579LM says 1 Gb/s but Windows shows 100 Mb/s?

The NIC supports 1 Gb/s, but the link negotiates to the slowest element. Check the NIC setting, router/ONT port speed, and especially the cable. A damaged 5 m run forced 100 Mb/s here. [Elektroda, Jozef2038, post #16930652]
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