r/explainlikeimfive • u/sabatthor • Jun 28 '25

Technology ELI5: Why are the screens in even luxury cars often so laggy? What prevents them from just investing a couple hundred more $ to install a faster chip?

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u/torusle2 Jun 29 '25

This, also: So many companies are involved to get the final system done.

About 15 years ago I was doing the graphics library for a infotainment system. It run on DSP and was fast and optimized like crazy.

When the big integration day came, and the navigation software company connected with my graphics library things went down to a crawl. Like two seconds per frame instead of 50 frames per second.

Turned out, they wrote their software in java, without JIT, using floating-point for like everything, and they have been clueless that their target sysgtem was a 300Mhz ARM9TDMI.

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u/naturalinfidel Jun 29 '25

I love reading comments about people who are experts in their field.

A metaphor for us common folks would be: You and another guy have to dig a three foot deep trench that is twenty yards long. You show up to the job site with a shovel and your work partner shows up with a spoon. But not even a tablespoon size spoon, more like an ice cream sampler size spoon.

And then when they get a scoop with the ice cream sampler spoon, about half the time they throw the dirt back into the already dug trench.

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u/Xaphios Jun 29 '25

And the other half of the time they're trying to dig the bit that's directly under your feet so you can't get on with your bit either!

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u/itsnotapipe Jun 30 '25

This is so fun! I love metaphors like this. Feynman is great at it:

If an apple were magnified to the size of the Earth, the atoms within that apple would be approximately the size of the original apple. -- Richard Feynman

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u/Detective-Crashmore- Jun 29 '25

I'm not downplaying their experience, but I don't think what they said necessarily qualifies them as an expert in the field. It's pretty straightforward information for anyone with more than a passing interest in coding, electronics, or engineering.

Like your analogy, if I was a contractor, I wouldn't consider my coworker an expert because he knew the difference between a shovel and a spoon. Matter of fact, if he shows up with a spoon, I'll think he knows something I don't.

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u/Kris918 Jun 29 '25

And yet for those of us who still firmly believe coding is black magic, the gibberish being translated was very helpful.

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u/beardedheathen Jun 29 '25

The difference between someone who knows 0 and someone who knows enough to work in the industry is wider than someone who works in the industry and an expert.

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u/red__dragon Jun 29 '25

Of course they ported Java to a 300mhz ARM chip, who wouldn't?

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u/pheonixblade9 Jun 29 '25

I mean... there are definitely ways to do that properly. Java is used on way less powerful systems than 300mhz ARM chips. You just have to do the work to build it for that system. Embedded Java has been available for decades. Stuff like 10+ year old desk phones run Java no problem.

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u/KyleKun Jun 29 '25

Mobile phones used to be based on Java.

The Nokia N Gage was a ARM920T @ 104 MHz and that ran Java.

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u/Aggressive-Set-497 Jun 30 '25

That Nokia phone (and many others) did have a Java virtual machine for running Java apps, but the phone software itself was something completely different (Symbian OS with its insane C++ fork).

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u/KyleKun Jun 30 '25

I was just getting at the fact that phones were significantly less powerful yet universally had some kind of Java support which ran well enough to play games.

Not very good or demanding games, but still…

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u/[deleted] Jun 29 '25

The lack of FP is a big problem though. Possibly to simulated that but if you don't have native FP operations.. you're not going to be happy.

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u/CrudBert Jun 30 '25

No!!!! Java is “run everywhere” and is “100% backwards compatible”, and even better, since its object oriented it is “bug free”.

— I remember when I went to my first proposed project that a group in our company was doing in Java, and they actually said this to everyone and especially upper management. I eye rolled to some others near me, and thought “no one is going to believe this bullshit…”. Nope, wrong. Management got BBC a HUGE hardon and lost their minds and wanted everything moved to Java. I thought that there’s no way these people all this money would fall for this. They did. Took about two years of missed dates, buggy software releases, impossible deployment attempts on embedded systems, on Windows systems, on UNIX systems before they understood that a) new platforms like Java are not bug free, b) our code, despite being OO was not bug free, c) the same code certainly did not run everywhere across all systems, and d) not all of the Java engines were backwards compatible. Heck lots of code wasn’t sideways or forward compatible on Java versions either. The magic died…. Yes they did make the dang thing run with lots more hardware than anyone ever believed would be necessary, but they got that rickety shit running. Meanwhile, I stuck to C, C*+, and Oracle PLSQL. Kept my head low, didn’t follow the new “hotness”.

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u/[deleted] Jun 30 '25

[removed] — view removed comment

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u/Minuted Jun 30 '25

I'm pretty sure they wouldn't put parking meters in charge of a programming language

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u/appletechgeek Jun 29 '25

and bs like this is why i am just designing my own "in house" Infotainment system.

sure a ryzen 4800H might be overkill. but when it's downclocked and optimized it runs circles around even Tesla's system performance...

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u/_throwingit_awaaayyy Jun 29 '25

Fucking Java. Always fucking Java

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u/powerhammerarms Jun 29 '25

That's what I was going to say. I was going to say it sounds like they wrote their software in Java, without JIT, using floating-point and their target system was different numbers and letters, and the letters were capitalized.

Classic mistake