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Mac Screens of Death History and Why Computers Crash

Feb 27, 2020
- Greetings, Internet. I'm Ken from the Computer Clan, and today I'm going to sho-- I'm sorry. I only had to reboot there for a second. Anyway, I want to show you today the Mac




, how they've changed over time, how they work, and what you might be doing to trigger them. Let's take a look at those right now. So where to start? Well, why not with the iconic Sad Mac display? This graphic was introduced with the original Macintosh and you would see it at startup if there was some kind of failure. And it usually happened with a


ing sound.
mac screens of death history and why computers crash
Also known as the


chime. Now you could activate it yourself by booting up a classic Macintosh and pressing the programmer key or later known as the break key. The power command button also activates this. This normally opens the MacsBug console, which is a debugging tool. But if you tried to turn this on at startup, you would see the Sad Mac and hear the death bell. So, next we have the bomb screen. This was also introduced with the original Macintosh and would occur due to a general system error. We'll talk more about them in a moment.
mac screens of death history and why computers crash

More Interesting Facts About,

mac screens of death history and why computers crash...

But if the system had a problem and couldn't keep running, you would get this bomb screen. And there was a reset button. You can click on it, and if you're lucky, the system will reboot itself. But not always. Those were the common error messages you'd see in classic macOS for a long time, but when the system was rewritten with macOS 10.0 and 10.1, a new type of error screen called a kernel panic appeared. In this case, registry information will be spit out on the screen if the operating system were to go into an unsafe state and basically have to shut itself down.
mac screens of death history and why computers crash
Now, before we get into that sort of thing, let's take a little break and talk about


es, crashes, and computer slowdowns. What are the suspects that actually cause those things? What actually happens when we see those


? Those death screens, if you will. What happens behind the scenes? Well, honestly, the answer is that there could be a million different reasons why a computer freezes or crashes, but I'm going to be pretty general and narrow it down to five suspects. Thrashing, deadlock, overflows, corrupted data, and viruses. Now, modern operating systems can be quite robust on these issues.
mac screens of death history and why computers crash
But any of these problems can occur in theory. Let's focus on these first three. I'll give you a general and simple explanation of everything with one of our cute mascots from the Computer Showdown cartoon, CHIP. Yeah, he'll help us today when he shows that tracing is part of the beating. I guess that will be our virtual memory subsystem for today. That sounds good. So when a system does paging, it's basically doing a data exchange between disk and RAM, but this can happen very often. Too much. In fact, it can be overwhelming when it happens over and over again and data is constantly being swapped between disk and RAM during a constant stream of paging.
This is called beating. And yes, it can cause a system to slow down or even crash altogether. So if you've ever experienced a slowdown, well, maybe thrashing is the suspect. And, yes, virtual memory subsystems don't like it when a thrashing happens. It sounds a bit violent, and it really is for a computer. Let's take a look at another scenario that won't necessarily crash a computer. It could, but not always. It will usually cause slowdowns or crashes. And that is called deadlock. So we have CHIP one and CHIP two here, right? We'll call them Program One and Program Two, and they want access to resources.
Resource A and Resource B. Well, Program One requires Resource A simultaneously with Program Two requiring Resource B, and everyone is happy. Well, now what if we have the awkward situation where both programs want each other's resources at the same time? One wants B on the condition that Two drops B, and Two wants A on the condition that One drops A. It can be a little weird. So now you are basically stuck until something else can help fix the problem. And again, modern operating systems can basically help move this along. And to keep it simple, I'll leave it at that.
You don't have to worry about that much with newer software and hardware, but if you've ever experienced a crash or maybe this son of a (beep), yeah, pardon my language, but, you know, we've all seen the spinning beach ball of death, right? That can sometimes occur during something like a stalemate or even during something like a beatdown. And yes, I know we all like to call it a beach ball, but technically, it's actually called a hold cursor, so sorry to burst your bubble. Anyway, what's another suspect? overflows. So we have a buffer and we have memory.
The buffer, or memory buffer, is basically a space that is reserved while memory data is exchanged between programs, sort of like a game of rackets. So what if the buffer is full? It's just getting too crowded, and it's like, oh no, there's another data set that has to come, and it's like, whoops, this is weird. Where do I put this? It will go to the buffer, but oh, actually it will overflow in memory and now we broke something. So now the OS state becomes insecure because some data was overwritten. Some important data in memory just got stepped on and now all the data is scrambled and corrupted and, you know, it might not be that bad, but it could cause some problems.
In this case, yes, yes, yes, CHIP is fine. CHIP will actually be fine. There is no need to worry. So those are three problems that could cause crashes, and there are some other common suspects like corrupted data, if your hard drive is dying and there are bad sectors on the drive or maybe you caught some malicious software that likes to cause some of these problems. simply because that's what the antivirus program is made for. Those are some of the things that can cause such problems and computer crashes. And as a result, you will see a death screen like a kernel panic.
So let's get back to these. So in 10.2 Apple actually simplified the kernel panic by making it a bit more graphical. Instead of always displaying that complex registration information, set a simple message in multiple languages. You need to restart your computer. Hold down the power button for several seconds or press the reset button. That's much easier for an In user to understand. Sometimes, depending on the severity of the problem, the computer will display registry information. But for the most part, it would just be a simple graph like this. In 10.3, the kernel panic received a minor design tweak.
It looks darker and actually had a similar animation to 10.2. So 10.2, 10.3, 10.4, 10.5, honestly they all had a very similar design. And the animation worked like this. It was like a little curtain that would drag across the screen and then, you know, I'd get this error message and you'd have to restart your computer. This changed a bit with macOS 10.6 and 10.7. So in 10.6, aka Snow Leopard, Apple added Spanish to the error screen. And in 10.7, resume was integrated into the kernel panic. So when the system crashed and had a kernel panic and you rebooted it, you would actually be prompted to resume any applications you had open at the time of the crash.
So if we take a look at this, we're going to simulate a kernel panic with a dtrace command, and you'll see that the system will crash. The kernel panic will happen, but then when we reboot, we have an option to basically pick up where we left off before the crash happened. And just for fun, let's put the system in verbose mode and run the simulation again with the dtrace command. Now you'll notice that we won't actually get a graphical crash. In fact, we will get the registration information displayed on the screen. And notice, it mentions the dtrace that we were using earlier to basically simulate this crash and boot argument, -v.
That means we were in verbose mode. And in 10.8, actually, also 10.13, which as of the day of this Tidbytes video, is the latest, newest, and perhaps best operating system on macOS, we have this kernel panic. It has a slightly different message because instead of asking someone to restart the computer, the computer actually restarts automatically and this is displayed on the boot screen. And it says, "Your computer restarted due to a problem. Please press a key or wait a few seconds to continue starting up." Resume was still built in so you could basically open all your apps again like nothing happened.
But now a further step has been taken. It will automatically restart if there is a problem. It will close. You'll hear the chime, see the message, and if the system can continue, you'll see the apple and you're ready to go. So there are other little death screens that we don't always want to see. In 10.2, we got the prohibition sign, which some people call the ghostbuster symbol, and this basically means that your system is corrupted or there are some incompatible components causing it to not boot correctly. This type of error actually existed before 10.2, but graphically, it showed a broken folder icon.
I personally think the ghostbusters symbol is much cooler. And another thing that we really don't want to see is the system not found icon. The blinking question mark on the folder? Yes, that means your system volume cannot be detected. So maybe you don't have anything installed on the computer, and you can't boot anything. Sure, you'll see. But what is a bit scary is if you have something installed and you see it. That probably means your hard drive is fried, so be careful with that. And before we had hard drives inside our Macs, we basically had floppy disks that we booted from.
So if the original Mac, for example, was waiting for a floppy disk to be inserted, you'd see a blinking question mark on a little floppy icon. So there you have it, guys. A brief


of the Mac screens of death. And I decided to make the video for the second edition, by the way, because a lot of people loved the first one. So thanks to you wonderful guys, that's why I made this here and now. And I hope you enjoyed. And hopefully the only time you see these death screens is in this video. That's all I have for you today.
Thanks for watching. And I will see you in the not too distant future.

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