2019 iMac download speeds only 10% of my Win10 computer's

[AirBear]

I've got a Win10 gaming rig and an 2019 27" iMac running 10.15.7. I have 1GB fiber optic from AT&T. Both computers are in the same room on the same network.

I left my iMac sitting for about a month in stby mode. Today I went to download some movies on it and noticed how slow the speed was. Speedtest.net showed around 80mbps. Thinking it was AT&T I ran speedtest on my Win10 machine. Over 800mbps. I switched the iMac from wireless to a RJ45 cable from the router. Same speed.

I rebooted, an error message showed up after reboot saying it was rebooted due to an error? I uninstalled Malwarebytes using their uninstall feature (it had lapsed anyway) and rebooted again. No change. I use Firefox so I shut that down completely and used MS Edge for speedtest. Same result. I have no other security software.

Don't know where to go from here. I could try restoring a month old time machine backup, or I could upgrade to Big Sur and see if that fixes it. Maybe something in the network settings? I have not had this problem before, always had good speed.

Youtube videos run just fine, I guess they don't need much speed.

TIA for any suggestions.

 

[chscag]

Try resetting the SMC on your iMac:

How to reset the SMC on Mac desktop computers

1. Choose Apple menu > Shut Down and wait for your Mac to shut down.
2. Unplug the power cord.
3. Wait 15 seconds.
4. Plug the power cord back in.
5. Wait 5 seconds, then press the power button again to turn on your Mac.

By the way, it's not a good idea to leave the iMac in sleep or standby mode for a month without use. I would shut it down.

 

[AirBear]

Thanks but that didn't make any difference. After doing the SMC reset I ran speedtest.net on Firefox, Edge, and Safari and all got around 90mbps down and up.

I hadn't intended to leave it in standby that long, kept thinking I'd need it any day. I will shut it down more often, this computer room frequently needs the window open in wintertime due to the heat produced by the two computers.

 

[chscag]

Resetting the SMC was worth a try. Check your Network settings from System Preferences but since this slow speed problem has just happened, I doubt anything could have changed there.

And lastly, if nothing else works to fix the problem give Apple Support a call.

I don't think installing Big Sur is going to cure things but you should keep up to date anyway.

 

[AirBear]

Think I found the issue. I booted the iMac from an external drive with 10.15.3 on it (using .7 on the regular drive). Same issue. Then I took my Win10 laptop and connected it to the RJ45 cable the iMac was using. Same speed issue. So I owe Apple an apology for all the cuss words I threw in their general direction.

I'll buy a new cable today. Now this doesn't explain the wifi speed unless it was actually using the cable with wifi turned on. Last night after turning off the computers I rebooted the router, wifi hub, and network switch. This morning the iMac with wifi only is getting around 400mbps. After I hook up the new network cable I'll see how it does.

As for Big Sur, I've installed H&R Block tax software and I don't want to risk screwing that up so I'll wait until taxes are done before upgrading.

Resetting the SMC was worth a try. Check your Network settings from System Preferences but since this slow speed problem has just happened, I doubt anything could have changed there.

And lastly, if nothing else works to fix the problem give Apple Support a call.

I don't think installing Big Sur is going to cure things but you should keep up to date anyway.

 

[chscag]

As for Big Sur, I've installed H&R Block tax software and I don't want to risk screwing that up so I'll wait until taxes are done before upgrading.

Good to hear you're making progress. At the speeds you're expecting, it's always best to check cabling especially RJ45 cables. I've run into more bad RJ45 cables in my work experience than any others.

And by the way, HR Block just put out an update to their software. I downloaded and installed it yesterday. Probably new federal information. (We do not have a state tax here in Texas.)

 

[AirBear]

I bought a 25ft length of Cat6 cable today. Totally fixed the speed problem, got over 800mbps download with the iMac's wifi turned off.

 

[chscag]

I bought a 25ft length of Cat6 cable today. Totally fixed the speed problem, got over 800mbps download with the iMac's wifi turned off.

Al right! Good job and troubleshooting.