Computers have gotten faster when it comes to computations—CPUs are astronomically more powerful today than they were in the early days of personal computing. Thanks to some painstaking tests by engineer and super nerd* Dan Luu, we now know of one area where computers have gotten slower: “the latency between a keypress and the display of a character in a terminal.”

Which is interesting.

Man touching a screen labeled "low latency."

In a blog post (via Gizmodo), Mr. Luu detailed his findings after months of testing every device he could get his hands on. Using two high-speed cameras, Mr. Luu tested how long it took for a character to appear on the display after after he pressed the key on the keyboard (virtual or real).

In the table below, you’ll see Apple’s venerable Apple //e—a device that was released in 1983—is the fastest of the 22 computers he tested. It took 30 milliseconds on the //e. Compare that to the 200 milliseconds it took on the PowerSpec G405 running Windows 10—a device released in 2017.

Dan Luu’s Latency Test Results

yearclock# T
apple 2e3019831 MHz3.5k
ti 99/4a4019813 MHz8k
custom haswell-e 165Hz5020143.5 GHz2G
commodore pet 40166019771 MHz3.5k
sgi indy601993.1 GHz1.2M
custom haswell-e 120Hz6020143.5 GHz2G
thinkpad 13 chromeos7020172.3 GHz1G
imac g4 os 9702002.8 GHz11M
custom haswell-e 60Hz8020143.5 GHz2G
mac color classic90199316 MHz273k
powerspec g405 linux 60Hz9020174.2 GHz2G
macbook pro 201410020142.6 GHz700M
thinkpad 13 linux chroot10020172.3 GHz1G
lenovo x1 carbon 4g linux11020162.6 GHz1G
imac g4 os x1202002.8 GHz11M
custom haswell-e 24Hz14020143.5 GHz2G
lenovo x1 carbon 4g win15020162.6 GHz1G
next cube150198825 MHz1.2M
powerspec g405 linux17020174.2 GHz2G
packet around the world190
powerspec g405 win20020174.2 GHz2G
symbolics 362030019865 MHz390k


There’s a reason for this, as Mr. Luu details on his wonderful blog: it takes more steps to get the character from keypress to screen now than it used to take. This especially true for operating systems designed to run on wide arrays of hardware.

Those extra steps are part and parcel of the many more things modern devices can do, however, and the reality is that few of us notice this lag.

Scroll Latency on Mobile Devices

Dan Luu also put together a table of scroll latency on just mobile devices and found that Apple’s hardware is the fastest in the land. Apple iPhones and iPads were had 8 of the top nine spots for screen latency, including the first 7. In fact, an iPad Pro 10.5-inch using Apple Pencil had the same screen latency as that old Apple //e, at 30 milliseconds. Second on the list, at 70 milliseconds, was iPad Pro 10.5-inches without an Apple Pencil.

The Google Pixel 2L—Google’s flagship smartphone? 110 milliseconds and tied for 12th. Coming in last on the list was the Kindle 4 at a staggering 860 milliseconds. Here’s the chart in full:

Dan Luu’s Chart of Scroll Latency on Mobile Devices

ipad pro 10.5″ pencil302017
ipad pro 10.5″702017
iphone 4s702011
iphone 6s702015
iphone 3gs702009
iphone x802017
iphone 7802017
iphone 6802014
gameboy color801998
iphone 5902012
blackberry q101002013
huawei honor 81102016
google pixel 2 xl1102017
galaxy s71202016
galaxy note 31202016
moto x1202013
nexus 5x1202015
oneplus 3t1302016
blackberry key one1302017
moto e (2g)1402015
moto g4 play1402017
moto g4 plus1402016
google pixel1402016
samsung galaxy avant1502014
asus zenfone3 max1502016
sony xperia z5 compact1502015
htc one m41602013
galaxy s4 mini1702013
lg k41802016
htc rezound2402011
palm pilot 10004901996
kindle paperwhite 36302015
kindle 48602011

I find all of this fascinating, and it’s a great reminder of two things: the first is that complexity can have a deleterious effect on speed. The second is that Apple’s mobile devices are way better than everyone else’s.


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I’d be interested in seeing the delay between a mouse click on a menu bar on an old GUI and a modern GUI ?


Not a terminal, but if you want latency try GEOS on that IIe. 🙂

Although I shouldn’t be too harsh because it was remarkable a GUI worked at all!