T420 always trottled to minimum

[samveen]

I've had an old BIOS locked T420 with an i5-2520M (off of ebay) that the kids were using for their virtual classes, off a 90W Power supply. Last year it's battery died, and last month it's CMOS battery died, so the BIOS setting got reset to their defaults.

When I opened it to replace the CR2032 in it, I also went ahead and removed the supervisor password from the BIOS(WITHOUT needing to access the bottom of the motherboard).

With the supervisor password gone, I was finally able to boot it into Linux, using a USB key(didn't wanna mess with dual-booting while the kids were using it). Examining the CPU information, I found that the CPU was constantly throttled to 800MHz instead of varying with load. When I checked the CPU temp, it was in the mid 40s (Celcius). Booting into Win10 again (off the boot disk), I checked, and I got similar results.

I had previously never paid attention to the CPU speed, not dug into the BIOS (due ti the lock). I did look into the BIOS now, but found nothing that would cause this.

What am I missing, and what other diagnostics might I run to figure out what's going on?

[RealBlackStuff]

In BIOS press F9 to set all Default, then press F10 to save it and exit.
Next go back in BIOS and check Config/CPU and Config/Power settings.

[axur-delmeria]

Question: does your T420 have a dead or missing main battery and a 65 watt charger?

[kfzhu1229]

I've also had ThinkPads that react unpredictablely if the battery is like very dead. I had a ThinkPad T60 that would randomly freeze because the power management triggered protection when the battery was like 0V dead (no cells are alive). And that T520 mobo of mine that doesn't charge batteries properly will throttle the CPU to the lowest speed when the battery is present and the board notices that it's not charging the battery properly even though the battery works, even on a 90W charger.

[samveen]

Question: does your T420 have a dead or missing main battery and a 65 watt charger?

Dead Battery, 90W power brick.

I've also had ThinkPads that react unpredictablely if the battery is like very dead. I had a ThinkPad T60 that would randomly freeze because the power management triggered protection when the battery was like 0V dead (no cells are alive). And that T520 mobo of mine that doesn't charge batteries properly will throttle the CPU to the lowest speed when the battery is present and the board notices that it's not charging the battery properly even though the battery works, even on a 90W charger.

I'm trying to get a couple of spare T420 batteries to try and re-cell them. If that alleviates the issue, nothing like it, but it'll take some time to complete if at all.

[kfzhu1229]

I'm trying to get a couple of spare T420 batteries to try and re-cell them. If that alleviates the issue, nothing like it, but it'll take some time to complete if at all.

well good luck with that. Just telling you it will be at least with a few of these battery packs before you can get all the experience you need and build a battery that is 100% safe. I hope you have a spot welder and good quality battery cells as for your first experiment you really have no room for more errors like with a cold solder joint or something.

[samveen]

well good luck with that. Just telling you it will be at least with a few of these battery packs before you can get all the experience you need and build a battery that is 100% safe. I hope you have a spot welder and good quality battery cells as for your first experiment you really have no room for more errors like with a cold solder joint or something.

Thank you. I really do need it.

Over the last 4 years, I've collected
- a set of known good 18650s from Samsung
- A spot welder kit from a maker in Germany (I'll try and find the link to it)
- An 18650 charger with good ratings.

What I haven't yet collected it the courage to go ahead with a test build .

[kfzhu1229]

Over the last 4 years, I've collected
- a set of known good 18650s from Samsung
- A spot welder kit from a maker in Germany (I'll try and find the link to it)
- An 18650 charger with good ratings.

What I haven't yet collected it the courage to go ahead with a test build .

Well funny thing I don't actually have a proper 18650 charger - I just have power banks that has a convenient slot for 18650 batteries without soldering, and then scrap cells in both fully charged and very discharged states if I need to quickly bring the charge up or down. And the cells and spot welding are done by the same seller so effectively that's "outsourced"
As for ThinkPad related battery rebuilds, I will have a T400/R400 4 cell rebuild coming up and will be documenting that if that went successful. I was originally gonna rebuild the 6 cell but the bms died just before I was gonna tear it apart... I was gonna say thinkpad T6x bms are aggressive but actually the cells were indeed dying and were spilling their guts, fair enough I guess it couldn't just have lasted a little bit longer...
The 4 cell is going to be extra challenging as there are more wires to keep track of and the layout of that is pretty weird.