1440p T490 Panel in T495?

[Big McLargeHuge]

I recently ordered a T490 with a busted screen, I then decided I'd rather have a T495 as my personal laptop and that I'd just sell the T490 (which I ordered a B140QAN02.0 panel for). Lo and behold I have now been told the T490 can't be shipped to me for some reason, so I'm stuck with the panel and a T495 (also with a busted screen) on the way. I shouldn't have any issues just buying a 40 pin cable (the T495 has a 30 pin I believe) and using this panel instead right?

[axur-delmeria]

The T495 reference sheet only mentions 1920x1080 screens, not 1440p. There's no guarantee that it will work, especially with Lenovo seemingly crippling AMD variants this way-- I remember reading a post somewhere about a T14s AMD system board having only half the number of coupling capacitors soldered on its eDP connector compared to the Intel variant. This meant that the AMD hardware was designed to handle 1440p (perhaps even more) but artificially limited during manufacture.

[Big McLargeHuge]

The T495 reference sheet only mentions 1920x1080 screens, not 1440p. There's no guarantee that it will work, especially with Lenovo seemingly crippling AMD variants this way-- I remember reading a post somewhere about a T14s AMD system board having only half the number of coupling capacitors soldered on its eDP connector compared to the Intel variant. This meant that the AMD hardware was designed to handle 1440p (perhaps even more) but artificially limited during manufacture.

Oh yo, hot tip, when you say connector I assume you mean the connection point on the MOBO rather than the cable itself? I'd be very keen on if there's any more info on this/anyone else knows something. It'd be within my power to do some piggyback/deadbug mods on the MOBO to overcome the issue but I'd need technical details (and I'd also rather not spend hours circumventing stupid anti-competitive design practices if it can be avoided).

[axur-delmeria]

Oh yo, hot tip, when you say connector I assume you mean the connection point on the MOBO rather than the cable itself? I'd be very keen on if there's any more info on this/anyone else knows something. It'd be within my power to do some piggyback/deadbug mods on the MOBO to overcome the issue but I'd need technical details (and I'd also rather not spend hours circumventing stupid anti-competitive design practices if it can be avoided).

Yes, connection point on the system board. I just checked my browser history and someone mentioned it in the comments of this Hackaday article: https://hackaday.com/2024/09/29/thinkpa ... /#comments

This reminds me of the delightful surprise I got with a T14 (AMD) when I looked into swapping in a higher resolution panel I had from a T490.

On the AMD T14s they leave the capacitors for half the eDP lanes unpopulated; while they are fully populated on the Intel based T14s. iGPU supports 4 lanes without trouble; and it’s a 40 pin connector in both cases; but they just had to spitefully break compatibility with higher resolution panels over what must be pennies worth of SMT capacitors.

...despite the display assemblies being identical across the T490 and gen1 and gen 2 T14s(aside from the different model name stenciled on the bezel between the T490 and 14); the AMD T14s were not configurable with higher resolution panels.

I’d be a little curious to know what the backstory was just because the crippling was so petty but so incomplete: they deliberately omitted a pittance worth of SMT caps; but still went to the trouble of routing all 4 lanes from the CPU package right up to the eDP connector; left the unpopulated pads in place, went with the 40-pin connector that supports 4-lane operation, etc.

Not sure if they made the decision to enforce segmentation in hardware fairly late in the game; if they expected that things might change before they did a motherboard revision; or if the one-time cost of routing those traces wasn’t a big deal but they actually saved money on all the capacitors they didn’t ship.

I think it's best to look for schematics and board views of the T490 and T495.

[Big McLargeHuge]

Oh this actually looks trivial, I also found: https://www.reddit.com/r/thinkpad/comme ... 140qan023/

Just a case of slapping a few SMD caps into positions they didn't populate (in hindsight they obviously wouldn't design an entirely different board). Not sure if I'll find any in depth technical specifics online but I'm electronics savvy enough to investigate this myself. Should be able to find and visually confirm absence of the caps, then can desolder and measure one to confirm it's also 100nF as in the T14 above and populate the other lanes. I'll update the thread with my findings/results when EBay's glacial international shipping gets the laptop to me.