Screen Latency Through the Ages: Computers Have Gotten Slower Since the Apple IIe

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.

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
computer	latency (ms)	year	clock	# T
apple 2e	30	1983	1 MHz	3.5k
ti 99/4a	40	1981	3 MHz	8k
custom haswell-e 165Hz	50	2014	3.5 GHz	2G
commodore pet 4016	60	1977	1 MHz	3.5k
sgi indy	60	1993	.1 GHz	1.2M
custom haswell-e 120Hz	60	2014	3.5 GHz	2G
thinkpad 13 chromeos	70	2017	2.3 GHz	1G
imac g4 os 9	70	2002	.8 GHz	11M
custom haswell-e 60Hz	80	2014	3.5 GHz	2G
mac color classic	90	1993	16 MHz	273k
powerspec g405 linux 60Hz	90	2017	4.2 GHz	2G
macbook pro 2014	100	2014	2.6 GHz	700M
thinkpad 13 linux chroot	100	2017	2.3 GHz	1G
lenovo x1 carbon 4g linux	110	2016	2.6 GHz	1G
imac g4 os x	120	2002	.8 GHz	11M
custom haswell-e 24Hz	140	2014	3.5 GHz	2G
lenovo x1 carbon 4g win	150	2016	2.6 GHz	1G
next cube	150	1988	25 MHz	1.2M
powerspec g405 linux	170	2017	4.2 GHz	2G
packet around the world	190
powerspec g405 win	200	2017	4.2 GHz	2G
symbolics 3620	300	1986	5 MHz	390k

lolwut?

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
device	latency (ms)	year
ipad pro 10.5″ pencil	30	2017
ipad pro 10.5″	70	2017
iphone 4s	70	2011
iphone 6s	70	2015
iphone 3gs	70	2009
iphone x	80	2017
iphone 7	80	2017
iphone 6	80	2014
gameboy color	80	1998
iphone 5	90	2012
blackberry q10	100	2013
huawei honor 8	110	2016
google pixel 2 xl	110	2017
galaxy s7	120	2016
galaxy note 3	120	2016
moto x	120	2013
nexus 5x	120	2015
oneplus 3t	130	2016
blackberry key one	130	2017
moto e (2g)	140	2015
moto g4 play	140	2017
moto g4 plus	140	2016
google pixel	140	2016
samsung galaxy avant	150	2014
asus zenfone3 max	150	2016
sony xperia z5 compact	150	2015
htc one m4	160	2013
galaxy s4 mini	170	2013
lg k4	180	2016
packet	190
htc rezound	240	2011
palm pilot 1000	490	1996
kindle paperwhite 3	630	2015
kindle 4	860	2011

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.

*😍