Internet speeds slower than on Win10

I have a situation I need help on. I have Optimum/Cablevision as my ISP with Ultra300 for internet speed. On my Late 2009 27"iMac (macOS High Sierra 10.13.6) I consistently got 120-130 download speeds. Optimum came out and tested the cable and modem and it clocked at 500 download. So that pretty much ruled out Optimum fault. My work laptop is on Win10 and when I run speedtest, I get closer to 300 (260 - 275) on download speeds.

This rules out router and cable modem issues. All these tests are run over Ethernet connection (I am not looking for advice related to Wi-Fi speeds). Link speed is 1Gbit/sec:

I tried to change the MTU settings in the Network Settings to Jumbo 9000 - this seems to have helped a little bit; now my iMac shows 175-180 on download speeds.

But it is still nowhere near the speed that Win10 unit shows.

Question: Is there anything else I can do to tweak macOS settings to allow higher internet speed, since it is obviously something within macOS?

iMac, OS X El Capitan (10.11.1)

Posted on Aug 29, 2018 2:20 PM

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19 replies

DmitriK Author

Level 1

13 points

Aug 30, 2018 5:07 PM in response to QuietMacFan

Before it turns into massive Win vs Mac fan fight let me point out a few things from my post (reading IS fudamental and alas, American education system IS failing us)

I never said I was using Windows tools to measure speed. All testing comes thru speedtest.net (one MIGHT surmise that results should be close).

I did make an extra effort to illustrate my question with screenshots and just in case we missed it, late 2009 iMac uses NVIDIA MCP79 chip for 1000baseT (might want to refresh your read-up on HW). This chip has been known to slow connections down (do a search on this in other discussions).

How can we know that iMac is NOT running top speed? It seems logical that if both units connect to the same router port over same CAT6 cable (as a matter of fact during all tests I connect it directly to cable modems Ethernet port to bypass the router entirely) and one is running 265mbps and the other barely reaching 180 - then the latter IS running slower. Call me stupid again, but seems obvious to me.

I DID state that all tests are run of Ethernet and I am not looking answers about wi-fi or bluetooth or firewire or anything else.

ISP clocking 500 at the output of the cable coming into the house is indeed an inconsistency, but my account is for 300 so I not worried about this. As a matter of fact, more speed coming to the house should potentially give me even higher readings on apple 1000 baseT adapter, but it does not.
[Edited by Host]

DmitriK Author

Level 1

13 points

Aug 30, 2018 5:09 PM in response to dialabrain

yes, and if I disable it, it adds 20-30 megs, so from 170 I was able to push it to 190. Aside from the usefulness of AV software on Mac (totally different discussion), difference in my opinion is insignificant. Although, good point!

rccharles

Level 6

13,037 points

Aug 30, 2018 9:58 PM in response to DmitriK

Interesting to find out the results. Solved that one user's issue.

We need to see your etrecheck report. It could be your machine is over extended. I could be flat out of cpu cycles.

Folks around recommend malwarebytes and etrecheck. All other anti-virus software has been shown to have problems around here. Apple has all the malware protection that you need. Malwarebytes has a stricture definition for adware than Apple does.

On my Late 2009 27"iMac (macOS High Sierra 10.13.6)

This is an elder machine. It may not be able to run HS as fast as you hoped. You should get an external drive and install what ever os came with the machine or lion and see how the test comes out.

Or, don't sweat it. I have a 50meg fiber link & it's ok for me.

DmitriK Author

Level 1

13 points

Aug 30, 2018 5:08 AM in response to rccharles

-- same cable

--same router port

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Internet speeds slower than on Win10