iMac 2020, 5700XT - graphical glitch?

[costica1234]

Oh, wow, didn't know that! I'm used to my MBP which I'm trying to keep on iGPU as much as I can because otherwise it gets very hot...

 

[PieTunes]

Oh, wow, didn't know that! I'm used to my MBP which I'm trying to keep on iGPU as much as I can because otherwise it gets very hot...

Yep, as far as I know, graphics switching capability is something for higher end MacBook Pro models like the 16”, and iMacs exclusively use a dedicated card.

 

[kkh]

Just saw one of them white line flashes in Logic. But, this happened after opening Safari, with its window on top of Logic. So, the theory about the white lines in inactive areas seems to hold. Doesn't matter if it's the desktop or an inactive app, it seems.

 

[kkh]

Just saw one of them white line flashes in Logic. But, this happened after opening Safari, with its window on top of Logic. So, the theory about the white lines in inactive areas seems to hold. Doesn't matter if it's the desktop or an inactive app, it seems.

Actually, never mind. Another white line in Logic while not running anything else on top of it.

 

[PBG4 Dude]

Actually, never mind. Another white line in Logic while not running anything else on top of it.

White lines and music have a storied history together. ;-)

Hope the issue gets resolved soon. Mine just moved to preparing to ship.

 

[kkh]

White lines and music have a storied history together. ;-)

Cocainegate.

 

[PieTunes]

White lines and music have a storied history together. ;-)

Remember what the dormouse said!

I too hope it’s a simple fix, like a driver/coding tweak that can be rolled into a supplemental update. It’s plausible Apple can do that before the release of Big Sur. Crossing my fingers.

 

[costica1234]

Yep, as far as I know, graphics switching capability is something for higher end MacBook Pro models like the 16”, and iMacs exclusively use a dedicated card.

Yes, on my mid-2015 MBP I'm simply running

pmset -a gpuswitch 0

inside the Terminal to run on iGPU only. Changing 0 to 1 forces the dGPU to run, while 2 enables auto switching (the default behaviour). Perhaps you can't run the same command on an iMac if the iGPU is truly disabled.

 

[torifile]

Actually, never mind. Another white line in Logic while not running anything else on top of it.

While it was the active window?

 

[kkh]

While it was the active window?

Yep. The main Logic window with no other windows open at the time.

 

[Conradiminja]

/////

 

[kkh]

Does this look similar to the flickering you experience? It's EXTREMELY fast but you notice it in the corner of your eye. So far what seems to be working is running on a lower scaled resolution (using switchResFX to run my external display at 2500x1400 instead of 2560x1440) which has reduced the flickering drastically.

Very similar if not identical. The more I do in any app, the more frequently I see it.

 

[joevt]

Does the iMac 2020 use DSC with the internal display? I would think not but double check with the AGDCDiagnose command.

 

[kkh]

Does the iMac 2020 use DSC with the internal display? I would think not but double check with the AGDCDiagnose command.

How can you tell for sure?

dsc_support is set to YES

the rest of the DSC properties:

[...]
000060: 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
Reg: 000060: 00 : DSC Support: 0
Reg: 000061: 00 : DSC Algorithm revision: 0
Reg: 000062: 00 : DSC RC Buffer Block size: 0
Reg: 000063: 00 : DSC RC Buffer size: 0
Reg: 000064: 00 : DSC slice Capabilities 1 : 0
Reg: 000065: 00 : DSC Line buffer bit depth: 0
Reg: 000066: 00 : DSC Block prediction support: 0
Reg: 000067: 00 : DSC Maximum bit per pixel: 0
Reg: 000068: 00 : DSC Maximum bit per pixel: 0
Reg: 000069: 00 : DSC Decoder color format capabilities: 0
Reg: 00006a: 00 : DSC decoder color depth capabilities: 0
Reg: 00006b: 00 : DSC Peak Throughput: 0
Reg: 00006c: 00 : DSC Maximum Slice width: 0
Reg: 00006d: 00 : DSC Slice capabilities 2: 0
Reg: 00006e: 00 : Reserved: 0
Reg: 00006f: 00 : DSC Bits per pixel increment: 0
[...]
000160: 0x00
Reg: 000160: 00 : DSC Enable: 0x0
[...]
00020f: 0x00
Reg: 00020f: 00 : DSC Status: 0
[...]

 

[joevt]

How can you tell for sure?

dsc_support is set to YES

the rest of the DSC properties:

[...]
000060: 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
Reg: 000060: 00 : DSC Support: 0
Reg: 000061: 00 : DSC Algorithm revision: 0
Reg: 000062: 00 : DSC RC Buffer Block size: 0
Reg: 000063: 00 : DSC RC Buffer size: 0
Reg: 000064: 00 : DSC slice Capabilities 1 : 0
Reg: 000065: 00 : DSC Line buffer bit depth: 0
Reg: 000066: 00 : DSC Block prediction support: 0
Reg: 000067: 00 : DSC Maximum bit per pixel: 0
Reg: 000068: 00 : DSC Maximum bit per pixel: 0
Reg: 000069: 00 : DSC Decoder color format capabilities: 0
Reg: 00006a: 00 : DSC decoder color depth capabilities: 0
Reg: 00006b: 00 : DSC Peak Throughput: 0
Reg: 00006c: 00 : DSC Maximum Slice width: 0
Reg: 00006d: 00 : DSC Slice capabilities 2: 0
Reg: 00006e: 00 : Reserved: 0
Reg: 00006f: 00 : DSC Bits per pixel increment: 0
[...]
000160: 0x00
Reg: 000160: 00 : DSC Enable: 0x0
[...]
00020f: 0x00
Reg: 00020f: 00 : DSC Status: 0
[...]

Looks like DSC is not being used (DSC Enable: 0x0) because the display doesn't use DSC (DSC Support: 0). Errors in decompression would probably appear as static/colored columns.

Check the section showing the connected ports of the AMD card (4 or 6 ports). For a 5K display that doesn't use DSC and supports 10 bpc, it should show two HBR2 connections. Each connection does 2560x2880 to make a 5K display.

 

[PieTunes]

Here's a video of the flickering corner as I slowly move Mail up and down. Here you can see it clearly going between a version with correct alpha and no alpha. But sometimes, it is not on/off like this but you get random pixels flickering. Only limited to the rounded corner area. Sometimes accompanied with the fast white lines on the desktop.

Yep, I was able to duplicate this, in both light and dark modes. Seems to happen when you move the window around slowly, then you would see the pixels "square off" the rounded portion for a little bit when you stop moving the window, and maybe if you start moving it again then they would disappear for a bit before coming back.

I hope that little glitch and the random flashing white lines can be fixed in a software update!

 

[haddy]

Yep, I was able to duplicate this, in both light and dark modes. Seems to happen when you move the window around slowly, then you would see the pixels "square off" the rounded portion for a little bit when you stop moving the window, and maybe if you start moving it again then they would disappear for a bit before coming back.

I hope that little glitch and the random flashing white lines can be fixed in a software update!

I guys what OS are you runing? Does this happen running 10.15.6?

 

[PieTunes]

I guys what OS are you runing? Does this happen running 10.15.6?

Yes, the 2020 iMacs come preloaded with 10.15.6, and I saw the glitch while setting up the machine. I still saw it happening after applying the supplemental update that came out on the 12th.

 

[kkh]

Looks like DSC is not being used (DSC Enable: 0x0) because the display doesn't use DSC (DSC Support: 0). Errors in decompression would probably appear as static/colored columns.

Check the section showing the connected ports of the AMD card (4 or 6 ports). For a 5K display that doesn't use DSC and supports 10 bpc, it should show two HBR2 connections. Each connection does 2560x2880 to make a 5K display.

Everything looks about right in that whole AGDCDiagnose dump. Here's the HBR2 stuff.

[...]

Vendor: AMD [00001002]: DiscreteGPU [2 30000] (0)
FBs: 4, Ports: 0x1e mst:0x1e ddc:0x1e aux:0x1e, Streams: dp:6 dvi:4 mst:6 max:6
Framebuffers:
* 0: Address: 1.0 Stream: Enabled Group: 0 Online Assoc'd Grouped
1: Address: 0.0 Stream: Not Associated Group: -1 MayGroup
2: Address: 0.0 Stream: Not Associated Group: -1 MayGroup
3: Address: 0.0 Stream: Not Associated Group: -1 MayGroup
Port Capabilities:
* 1: AUX, DDC, MST
* 2: AUX, DDC, MST
3: AUX, DDC, MST
4: AUX, DDC, MST
Connections:
* 1: [DP 1.2 4 x HBR2] Status: [4 x HBR2 7777] caps [features 0x103141f, p_encoding 0xd] Sink OUI:000-016-250 MN27i1 [077-078-050-055-105-049] HW Version: 16 FW Version: 1.1
* 2: [DP 1.2 4 x HBR2] Status: [4 x HBR2 7777] caps [features 0x101141b, p_encoding 0xd] Sink OUI:000-016-250 MN27i1 [077-078-050-055-105-049] HW Version: 16 FW Version: 1.1
3:
4:

[...]

 

[Conradiminja]

/////

 

[kkh]

Also, to confirm: my machine with this issue came from Ireland. Apple seems to be assembling these machines in both China and Ireland. Luck of the Irish?

 

[RossH51]

Here's a video of the flickering corner as I slowly move Mail up and down. Here you can see it clearly going between a version with correct alpha and no alpha. But sometimes, it is not on/off like this but you get random pixels flickering. Only limited to the rounded corner area. Sometimes accompanied with the fast white lines on the desktop.

Now that you have highlighted it, I can see this clearly on the top LH corner of Mail. I don't see it on Finder. Now I just have to unsee it!
2020 iMac i7 with Radeon Pro 5700XT

 

[kkh]

Yep, I was able to duplicate this, in both light and dark modes. Seems to happen when you move the window around slowly, then you would see the pixels "square off" the rounded portion for a little bit when you stop moving the window, and maybe if you start moving it again then they would disappear for a bit before coming back.

I hope that little glitch and the random flashing white lines can be fixed in a software update!

I do hope so. Would hate having to ship this back.

 

[kkh]

Now that you have highlighted it, I can see this clearly on the top LH corner of Mail. I don't see it on Finder. Now I just have to unsee it!
2020 iMac i7 with Radeon Pro 5700XT

Such a beautiful beast of a machine! But it's like getting a new car with dings. Dings that flicker.

 

[torifile]

I just spent about 5 hours in Windows 10. No sign of the graphical glitch. I played assassin’s creed odyssey for over an hour on ultra high settings in 1440p (on my secondary display) and no white lines.