My two desktops, lap and desk are updating painfully slow. Is this tied completely to model speed? Today is a slow 4 mpbs.

What do you mean by "updating"? Are you referring to download speeds on the internet? Something else?

Which specific models do you have? How much RAM in each? How are you connected to the internet (wireless? wired?).

Let's say have few images on desktop, usually they'll be there on the desktop a few minutes later, not few hours later.

Start up in Safe Mode and see if that resolves the problem. I am puzzled that this happens on both computers.

But... before troubleshooting unknown solutions...

Is this tied completely to model speed?

The speed may be affected by a damaged directory, corrupted caches, or other miscreants. Safe Mode is, well, safe. You won't do any harm by trying it. During the lengthy startup into Safe Mode, the equivalent of Repair Disk is done and caches are cleared (among other things). If all goes well in Safe Mode, restart normally to see if the problem is solved.

I haven't has my afternoon Starbucks Expresso but I am not following your explanation.

• Are you opening these images in an Application and if so what application?
• How many images are you opening simutaneously?
• Are you downloading these images from the internet? …from iCloud?
• From a specific web site such as imgur?
• To reiterate jon's questions
  • Which specific models do you have?
  • How much RAM in each?
  • If these are coming from the internet, how are you connected to the internet (wireless? wired?).

thanks Joe no. I bring in the images from a flash drive onto the laptop into a folder on the desktop, thats it.

Now for years this feature that later you would see live what you have on one the laptop, on the desktop did not exist, but I've grown to like it. Usually its normal/ fast. But sometimes it take a day or so for say a folder of 120 images on the laptop to appear as 120 on desktop.

I'm confused (not unusual this early in the morning, and I drink Oren's coffee, not Starbucks). You said that this occurs on both computers, correct? Does it occur only with that particular flash drive? If so, that would indicate that the flash drive is defective.

Since there is only one common element involved, the flash card, as Jon said "that would indicate the flash drive is faulty". Before the drive fails completely and you lose all 120 images spend however much time it takes to copy the files to one of your computers then copy them to a new flash drive and see if that doesn't improve the display speed.

NOTE: each open image on your desktop requires memory and that many images together with any open applications could force your computer(s) to make heavy use of Swap Files on the disk drive which will cause everything to run slower. Open Activity Monitor, select the Memory tab, and see how much Swap is being used and what the "Memory Pressure" looks like. There is a possibility that a new or updated application is eating up your memory and thereby creating or at least contributing to the slowdown.

Just to clarify, where are you seeing this "slow 4 mbps" and what do you usually see?

Thanks Joe, others, this has nothing to do with a flash drive. I do a photo shoot 200 images. I take drive and download the folder to the desktop of laptop Macbook Air.

Normally, I'll see this folder in a few hours with 200 images on the decktop in the other room. But sometimes is takes a day..

Again this feature of the two desktops mirroring is new, just last OS or so right?.

Yesterday, I dragged just 1, 1 attachment to the laptop desktop Macbook Air. And waited in the other room for it to appear on the desktop of the imac-- it took 20 min! It was only 8kb. So I'm wondering when it slow, why is it slow? I thought maybe modem? or something with icloud is off?

As an experiment, what happens if you if you reverse your procedure, i.e. download to the desktop in the other room and see how long it takes to get to the desktop of the Macbook Air?

I think the we are just about through the vocabulary fog to understand what you are describing. There is one question remaining for complete communication, "What specific

1. Desktop sharing methodology are you using?"
   1. Video Mirroring (available since Mavericks)
   2. Sharing the desktop folder via the iCloud Drive (available in Sierra & High Sierra)
   3. Screensharing (available for many years)
2. What is the connecting media?
   1. WiFi
   2. bluetooth
   3. ethernet
3. Have you performed any network speed checks?

Joe thanks, no method.. For 20 years if file was on my laptop, that file was not on my desktop on imac. The two desktops looked different. Then starting with Sierra? They mirror each other exactly.

On both devices go to System Preferences > iCloud > iCloud Drive > Options and see if "Desktop & Documents Folders" is checked (✓). That means both devices are actually sharing the same Desktop folder which is on your iCloud Drive. (This would fit your time frame when you say this began, but I don't believe it is the default, so at some point you would have had to select the specific option.)

In this scenario the Desktop on your device mirrors the Desktop folder on you iCloud Drive. In other words there is a physical copy of the Desktop Folder on both of your devices for speed and in case there is a network problem where iCloud Drive is not available. When you make a change to the Desktop Folder contents on Device A that change is copied to the iCloud Drive copy and then downloaded to Device B. There is an inevitable and unescapable lag or delay in copying the change from Device A to the iCloud Drive and an equally inevitable and unescapable lag or delay in copying the change from the iCloud Drive to Device B. In my experience each link takes a few seconds, but for a large file that can easily stretch to several seconds, even minutes to complete.

There are a number of other conditions that can effect when a change on Device A is reflected on the iCloud Drive and how long the upload and download take. Among the conditions are - in no particular order:

1. both devices connected to the internet
2. both devices are "awake"
3. other activity on either device such as a Time Machine backup in progress
4. speed of the internet connection of either device (they do not have to be on the same Local network or even in the same country)
5. in light of the number of images involved in your case, how much Swap File memory each of the devices has to use to render all the images (Go to Activity Monitor > the memory tab and see how much Swap is used and what the "Memory Pressure" level is
6. the traffic load on your internet service provider's network
7. the traffic load on Apple's iCloud servers and are those servers up

Assuming this is the desktop sharing technique you are using and given the fact sometimes the update time is relatively short and the long delays are relatively recent I would posit 3 possible causes of the delay

• A recently added or updated application on one or the other device has a memory leak forcing heavy use of Swap File memory (see item 4 above)
• intermittently slow, or even no internet connection (You can test this with apps such as Speedtest by OOKLA, Internet Speedtest )
• one of your devices has a weak, noisy, or poor WiFi connection to your Local Area Network and thereby to the internet (there are apps such as WiFi Explorer, WiFi Strength Explorer, Air Radar, etc.
• the Apple iCloud servers you are connecting with are have problems (you can check the current status here
• You can force the upload by logging onto your iCloud account in Safari opening iCloud Drive and clicking on the upload icon (a cloud with an upward pointing arrow) and selecting Desktop.
• You can force the download by logging onto iCloud in Safari, clicking on Desktop, selecting the images and clicking on the download arrow.

Thanks Joe, great analysis.

They are both checked.. just looked, sometimes things do get unchecked!

And I did test on simple screenshot right now 400k, and working in both directions super fast today.

Anyway, I'll keep you notes for future... so many variables as you point out why there can be lags. I'm making it a point to call ATT for a visit.. I always procrastinate that one and they are so difficult to deal with...