Thinkpads Forum

Hi everyone, I’m currently using a ThinkPad T520 and overall I’m pretty happy with it, but I keep wondering how it compares to the T400/T410/T420 series, especially the T420. For daily tasks like writing, browsing, and general work, does the T420 feel noticeably more portable or efficient in terms of battery life, and are there any trade-offs in performance, thermals, or screen quality compared to the T520? I’d really like to hear from anyone who has used both and can share whether sticking with the T520 is the better long-term choice or if the T420 has some advantages I might be missing.

Welcome to the forum.

T520 is the same thing as T420, only bigger.
Battery life will be essentially the same. The larger screen may consume slightly more battery, but other factors will have a bigger effect.
Stock T520 can be had with higher resolution (1920x1080 vs 1600x900 max for T420). To me it's quite meaningful.
Bigger screen may be more pleasant to use in general, but the machine is heavier, that might be the only downside.

t520 is a higher quality product imo

T520 is made for quad core and has way better cooling than the T420.

If you need need to save ~1 pound and ~1 inch in width, ~0.5 inches in depth and ~0.25 inches in thickness, and you need a quad core, then yes the T420 is perfect.
But if you need need portability, an X220 will do that job much better.
You are loosing out on a socketed CPU, meaning you lose on a simple upgrade to a quad core, but the T420's heatsink can't handle a quad core anyways.

Other than portability, T520 wins out on every other metric: performance, thermals, screen quality, workmanship.
To prove my point:
My T430 has hinge issues which have damaged the screen, my W520 is perfectly fine.
My T430's screen literally needs me to tilt the screen back and forth to read down the screen properly, my W520's screen doesn't.
At full load, my W520 (basically a T520 with a quad core) tops out at 80C with a 2740QM and a quadro 2000m but my T430 (basically a T420 but actually even runs cooler) with a 3340M and a NVS 5400M reach upwards of 90C or even thermal throttle. (Yes they both have fresh thermal paste)
Mind you, this is with a dual core on the T430. I can only imagine what will happen if I did put a quad core in it.
Meanwhile, the W520 brushes off the heat from the quadcore without a sweat.

Now, this is only one data point. My W520 could just be above average and my T430 could be below average, but I'm certain that others will back me up on what I've experienced.

i can back you up, ive always found the cooling in the T420, T430, also T410 to be awful, worse even than T500.

mind you most T520 and T530 were sold with a nerfed version of their heatsink good enough for the base spec dual core. you would have to upgrade to the better heatsink to get good enough cooling for the quad core. the W520/30 use an entirely different heatsink.

TPFanatic wrote: ↑

Fri Jan 16, 2026 8:53 am

i can back you up, ive always found the cooling in the T420, T430, also T410 to be awful, worse even than T500.

mind you most T520 and T530 were sold with a nerfed version of their heatsink good enough for the base spec dual core. you would have to upgrade to the better heatsink to get good enough cooling for the quad core. the W520/30 use an entirely different heatsink.

T500 with intel graphics has superb cooling (if you have the discrete graphics model heatsink)
T420 with intel graphics is ok as long as you have the discrete graphics heatsink

I own both the T420 and T520. Mods made to both include SSD, 16g memory. T520 only, ugraded cpu to i7 quadcore. T420 had bad lid and screen w/ lines going through it (it was a $10 yardsale buy) so I purchased an ebay lid/screen and lucked out (it was 1600x900).

So, my remarks for what they are worth on these machines.

The keyboard is that old school deep typing wonder on both and though both are slightly worn (well, the T420's is fairly well worn) they work like a charm.

The ports. Other than usb 2 only, they're great. Running external screen from either one is spectacular.

Okay, where things diverge some?

Weight. A bit over a pound difference, of course T420 weighs less. In lap, though, neither really is bad. I have much lighter old macihnes such as Macbook Airs from the 2012 to 2017 era, and they're very nice. So how come I end up back on my Thinkpads. Heh. Anyway, betwixt T420 and T520, win to the T420.

Size. Obvious, perhaps. But the T420 does fit in the lap a bit better than the T520.

More seriously, the screens. Both the T420 and T520 have a screen of 1600x900 (non-IPS). But, but, but. MAJOR difference in quality between them. The T420 is okay, but what I'd describe as a slight greyness is continually there. The T520's screen has deep full blacks and simply (no pun) outshines the T420 display in every way. So, T420's okay is okay until you see the T520.

Heat / CPU modding. I put an i7-2760QM quad core into my T520. Cost me about $20 via ebay. It doesn't run hot for me despite that addition. I did of course put new paste on the chip, which might help some. But I think the size and room inside the T520 has is the biggest reason. I do run linux (BigLinux currently) exclusively on both machines, which I believe helps heat also. The T420 is sporting only an i5, and does run a little hot, which means I'm less likely to pop an i7 quad core into it. T520 wins here, but not a deal-breaker if T420 has i5 or (likely) even i7.

Final Verdict. I can't choose. Even though on paper the T520 wins, that size thing in the lap is important to me. However, I really do like the T520's speed w/ the i7 and the much better display. So I guess I'm glad I can switch back and forth according to mood. Right now, I'm on the T520.

antelope77 wrote: ↑

Wed Apr 01, 2026 10:30 pm

I own both the T420 and T520.

do you see significant difference in performance when browsing with t520 with the quad compared to t420 with the i5 ?