Thats not correct, Apple does also limit active DP > HDMI 2.1 Adapters.
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Mac mini: 4k @ 120hz?
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Thats not correct, Apple does also limit active DP > HDMI 2.1 Adapters.
Yes, but not because of the MCDP2900 chip, but for some other reason or simple oversight or programming issue in the DCP. Afaik on Apple Silicon you can't do much about this at the OS side, the DCP (which is a part of the chip that does low level display stuff and among other things negotiates timings) needs to negotiate things differently, and that is a part of the system that is very much locked down and can be updated by Apple itself.
But we need apple to do the conversion or rather the macOS. The external dongle will get the input whatever the OS gives it. So while the dongle is capable of doing 4k/120 goodness , macOS is limiting it. If you try the same in windows , u get all the 4k/120 goodness.
@zamzam1235 - if I understand correctly, macOS is not doing anything really. For an external dongle, the conversion is done by the dongle's won DP Alt Mode -> HDMI 2.1 converter chip which translates everything. The Mac hardware communicates via the dongle using DP Alt Mode. What modes are accessible and how, those things are controlled by the rather complex and shady DCP part of the graphics architecture of the Apple Silicon chip. MacOS has some interfaces with the DCP and can ask it to do things or ask of things, but most of the stuff is done inside the DCP which is an entire chip by its own right with its own real time operating system and is locked and cryptographically sealed to prevent tampering. So this is not like on Intel where macOS drivers actually do things. But I might be wrong, I get these from the linux guys who worked hard figuring this stuff out.
Yes, it does not. But it would be great to know if it still has the same hardware or something else. It's relevant for some app developers like me who need to specifically handle the somewhat different way I2C communication (like DDC, EDID) happens when this chip is employed. I understand this is somewhat off-topic so sorry about that.
What could be interesting is to understand how the Apple Silicon DCP figures out that the connection is actually happening through a HDMI dongle or what other factors trigger it not to expose higher than 60Hz 4K resolutions if this is not something intentional. It might be how the DP Alt Mode -> HDMI2.1 chip configures DPCD registers or how the translated EDID looks like. Some insights into this could lead to correcting the issue thus producing a dongle that can actually fool the Mac to think it's a native DisplayPort connection and make 4K@120Hz a possibility even on M1 Macs.
It's a great market opportunity I think for hardware makers to investigate as many Mac users would flock to buy a dongle that could fix this issue.
It's a great market opportunity I think for hardware makers to investigate as many Mac users would flock to buy a dongle that could fix this issue.
@joevt - It seems to me you might be right, according to the chip's block diagram it looks like the chip can talk via a separate GPIO channel to handle some aspects of the communication although DP AUX channel is wired there as well so maybe it can work both ways as the chip has multiple applications (can be used inside a TV in a dongle, docking station or evidently as built-in hardware in a notebook or desktop). Maybe the use of GPIO is the reason why DDC works somewhat differently than other devices (on the Intel mini DDC with this chip is still unsupported as I don't have a Mac like that anymore to test if the tweaks required on M1 would work on Intel or not)? But it might be that the general purpose I/O is used only to manage the chip or do firmware updates and things like that. I did not find any deeper docs about the chip than the one linked earlier but maybe I did not dig deep enough.
(but even if in M2 macs a chip like this is not present or the new hardware does not have any GP I/O stuff needed so it does not show up this way in the I/O registry, investigating what's under the active DCP endpoint in the ioreg tree when a HDMI display is connected should shed some light on what we have in the new macs - if there is nothing distinctive there compared to DP dispext connections, that is telling as well as that would mean macOS is not even aware it's not an ordinary DP connection so whatever is doing the HDMI stuff is totally transparent).
It seems like the M2 Pro macs have a different hardware layout inside. When connected via HDMI, the connection's provider class seems to be AppleDCPPS190.
This would indicate that the DCP is wired to a PS190 (PS196?) DisplayPort 2.0 to HDMI 2.1 protocol converter.
www.paradetech.com
This device does not have a special GP I/O like the previous one and seems to communicate solely through the AUX channel (for stuff like DDC, EDID, etc and possibly firmware upgrade as well through `Parade’s licensed AUX-updater that utilizes highly encrypted firmware security` whatever that is.).
This would indicate that the DCP is wired to a PS190 (PS196?) DisplayPort 2.0 to HDMI 2.1 protocol converter.
PS196 - DisplayPort™ 2.0 to HDMI™ 2.1 Protocol Converter - Parade Technologies, Ltd.
PS196 is a DisplayPort™ 2.0 to HDMI™ 2.1 Protocol Converter that receives both video and audio streams over a DisplayPort link and converts to HDMI supporting either TMDS or FRL output signaling. The DP receiver supports up to 8.1Gbps link rate over 4 lanes. The HDMI output port can operate as a...
This device does not have a special GP I/O like the previous one and seems to communicate solely through the AUX channel (for stuff like DDC, EDID, etc and possibly firmware upgrade as well through `Parade’s licensed AUX-updater that utilizes highly encrypted firmware security` whatever that is.
).
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It's DisplayPort 2.0 but limited to HBR3 link rate. What features, if any, does DP 2.0 add in this case?It seems like the M2 Pro macs have a different hardware layout inside. When connected via HDMI, the connection's provider class seems to be AppleDCPPS190.
This would indicate that the DCP is wired to a PS190 (PS196?) DisplayPort 2.0 to HDMI 2.1 protocol converter.
PS196 - DisplayPort™ 2.0 to HDMI™ 2.1 Protocol Converter - Parade Technologies, Ltd.
PS196 is a DisplayPort™ 2.0 to HDMI™ 2.1 Protocol Converter that receives both video and audio streams over a DisplayPort link and converts to HDMI supporting either TMDS or FRL output signaling. The DP receiver supports up to 8.1Gbps link rate over 4 lanes. The HDMI output port can operate as a...
This device does not have a special GP I/O like the previous one and seems to communicate solely through the AUX channel (for stuff like DDC, EDID, etc and possibly firmware upgrade as well through `Parade’s licensed AUX-updater that utilizes highly encrypted firmware security` whatever that is.
This is interesting "Supports DP Adaptive-Sync Video to HDMI VRR conversion". I don't think other DP to HDMI adapters support VRR?
So if M2 Macs are using PS196, then it might be a good idea to find adapters that use the same chip but I don't think they exist yet for sale?
https://www.fullink.com/product/details/5-15-0-173
Actually, we talked about the PS196 a few months ago.
#463
Hi @joevt
I think it's just (barely enough) sufficient to have 8K@60Hz thanks to DSC even though the bandwidth is limited to 32GBps. The M2 can't seem to be able to handle anything faster anyway.
"The DP receiver supports up to 8.1Gbps link rate over 4 lanes (that's 4xHBR3 all right). The HDMI output port can operate as a TMDS or FRL transmitter. The FRL transmitter is compliant with the HDMI 2.1 specification supporting up to the maximum data rate up to 12Gbps per lane enabling display resolutions up to 10K@50Hz utilizing DSC pass-through mode."
I think it's just (barely enough) sufficient to have 8K@60Hz thanks to DSC even though the bandwidth is limited to 32GBps. The M2 can't seem to be able to handle anything faster anyway.
"The DP receiver supports up to 8.1Gbps link rate over 4 lanes (that's 4xHBR3 all right). The HDMI output port can operate as a TMDS or FRL transmitter. The FRL transmitter is compliant with the HDMI 2.1 specification supporting up to the maximum data rate up to 12Gbps per lane enabling display resolutions up to 10K@50Hz utilizing DSC pass-through mode."
But yeah, it's not clear to me what DP 2.0 brings to the table, maybe some misc things, but not UHBR for sure with this chip.
Although I'm not technically educated enough to understand most of the stuff you guys are investigating here, but I'm more than happy to read it. I own an M1 mac mini that is currently hooked onto my 42" LG C2. The only thing I'm actually missing is the damn option for 120hz. I'm sure you guys have already seen this video, but if you haven't, check it out. MacBook Pro 14" with M2 Pro chip with the LG C1. 120hz HDR10. As much as I don't feel like spending so much money on a new M2 Pro Mac Mini, I still thought about buying one, just to have 120hz on my LG C2. My concern is that I absolutely have no issues with my M1 mac mini, so replacing it just to have 120hz doesn't seem to be a really good idea.
macOS deliberately does not allow you to use the usb-c to hdmi 2.1 adapters, because they want you to upgrade.
Even though the adapter clearly supports 4k/120 on a windows machine.
I think there's little incentive for that product now that the M2 Macs offer a HDMI 2.1 port.
The PG42UQ is almost 2000 usd in my country, the LG C2 was on discount, got it for like 930 usd.
The PG42UQ has a 150 ppi compared to 105 ppi for the C2.
That makes a big difference long term on your eyes when reading text on the monitor/TV.
TV's usually have lower PPI for obvious reasons. The TV is just not a good idea to use it as a Monitor.
E.g on my LG OLED connected to hackintosh, anything above 1440p is horrible and frustrating to read. At the same time i still have an old 32 iMac and the text rendering and readable is far superior.
I think this is one the biggest mistake people make when buying a TV to use as a Monitor.