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• RAM stands for Random Access Memory and it provides storage for ongoing tasks and processes. The difference between the RAM and the rest of the storage on your Mac is that it's faster, therefore.
• How to free up memory on Mac. Knowing how to clear memory on Mac is important, especially if you have a Mac with limited resources. One option is using Activity Monitor: Open Activity Monitor on your Mac; Select an app using a lot of memory; Click the 'x' icon on the top left of the screen; This is straightforward, but there's a better way.

In the Activity Monitor app on your Mac, click Memory (or use the Touch Bar) to see the following in the bottom of the window: Memory Pressure: Graphically represents how efficiently your memory is serving your processing needs. Memory pressure is determined by the amount of free memory, swap rate, wired memory, and file cached memory.

Apple Lisa 2

The Lisa is the predecessor to the Macintosh. Released in 1983, the Lisa was the first commercial computer which utilized the advanced concepts developed at Xerox PARC a decade earlier: the GUI (Graphical User Interface), icons, menus and the mouse. Apple’s seminal workstation launched the next chapter of computing, and utilized features like pre-emptive multitasking and protected memory that the Mac wouldn’t get for nearly twenty years. But the Lisa wasn’t a big seller, cost $10,000, and was ultimately superseded at Apple by the Macintosh – the computer for the rest of us.

The VMM Lisa has an X/Profile Compact Flash adapter installed, to support running the Lisa OS long after the original Widget hard drive has given up the ghost. VMM Blog:At Last A Working Lisa! Mostly…

Clear Sided Mac 512k (HyperDrive Demo)

Before the Macintosh SE made its debut, there was no internal hard drive available for the compact Mac. Back in 1985 General Computer Corporation introduced the HyperDrive, an internal 10MB hard drive add-on. It wedged a 3.5-inch disk, power supply, logic board and fan inside the existing case, and was 7 times faster than Apple’s floppy-port based HD20. It also cost about the same price as the Macintosh itself, starting at nearly $2200 for the 512k – or $2800 for the 128k version, which upgraded you to 512K along the way.

This Mac model was a GCC trade show demo unit. The right and rear sides have been replaced by clear plexiglass panels, sporting graphics highlighting the HyperDrive components inside. It’s like a real world version of an engineering cutaway drawing! The hard drive and other electronics are long since gone, but the Mac is still working. This clear-sided beauty is a highlight of the Mac Museum’s collection.

Macintosh “Picasso” Dealer Sign and Packaging Artwork

The famous Macintosh Picasso logo was developed for the introduction of the original 128k Mac back in 1984. A minimalist line drawing considered to be in the style of Pablo Picasso, this whimsical graphic implied the whole of a computer in a few simple strokes. During roll-out of the Mac Apple used this artwork for manuals, software, packaging, etc.. They also produced a limited edition promotional sign for original Mac dealers, that has the Picasso line art along with the name Macintosh etched into a 10″ x 10″ piece of glass. Manually beveled and painted, the glass was mounted on a beige plastic base containing an internal fluorescent light, illuminating the glass from below.

Today these signs and original packaging using the Picasso artwork are popular on the Apple collectibles market. Ironically in 2014 the designer of this artwork, John Casado, revealed that it was actually Matisse, not Picasso, who was his primary inspiration for this graphical style!
VMM Blog:The Enduring Appeal of Macintosh Picasso Artwork

Outbound Notebook

The Macintosh Portable was Apple’s first entry into the notebook market, but it’s high price and hefty weight were obstacles to market success. Before the Luggable was replaced by the PowerBook several third party options appeared, including the Outbound Notebook. An early Mac clone produced under agreement with Apple, it required a genuine Macintosh ROM pulled from a working Mac Plus or SE. But even with that extra cost, the Outbound was nearly half the price of Apple’s offering ($3500 vs $6500), smaller, lighter and faster. Business users were pleased.

A unique feature of the Outbound was its pointing device, the TrackBar. Rather than a trackball or a trackpad, users slid their fingers left and right on a touch sensitive bar, which also rolled forward and backward, to move the cursor onscreen. Quite clever. And despite the kangaroo logo and down-under company name, Outbound Systems was actually located in Colorado, not Australia.
VMM Blog: An Outbound Notebook Comes In From the Cold

JLPGA PowerBook 170

In 1992 Apple manufactured approximately 500 multi-colored PowerBook 170 models to commemorate the Japanese Ladies Professional Golf Association (JLPGA) tournament. The JLPGA PB170 has the same innards as a standard 170, its rarity derives from the color case and that fact that only a small number were made. Replacing the standard battleship grey components are a dark blue palmrest and screen bezel, white top and bottom panels, yellow hinges, red sliding panels and green rotating feet. It is similar to the multicolor Apple logo color scheme and is really quite striking in appearance.

Also unique about this PowerBook is the Japanese keyboard. This was a promo item for the Japan so you don’t often see these keyboards outside that region. VMM Blog:A Rare Beast Captured: the JLPGA PowerBook 170

Macintosh TV

A black Mac! The Macintosh TV was a limited edition Performa 500 series all-in one, clad in a black case and including a TV tuner card. A Control Panel or supplied infrared remote control switched the whole screen between the Mac’s desktop, the TV tuner or a composite video input – no video-in-a-window on this puppy. Nothing the Performa couldn’t do, but Apple offered very few black machines during this period (or since) in North America (they were more popular in Europe), and it looked very cool! Unfortunately it was ahead of its time, and underwhelming performance plus slow sales led to a short lifespan. It has since become a desirable collector’s model.

At the VMM a Mac TV is connected to a DVD player running a loop of Apple TV commercials and demos.

Twentieth Anniversary Macintosh (TAM)

To commemorate the twentieth anniversary of Apple Computer, the company decided to release a special edition Macintosh. This limited edition model was Apple’s vision of the future, a flat panel screen design with a vertical computer behind the screen. It included advanced AV capabilities like an FM/TV tuner and a custom Bose sound system, but with a $7500 price tag even home delivery by a tech-in-a-tux wasn’t enticing enough to attract buyers. The price of the computer dropped to as low as $1995 before Apple pulled the plug a year later.

Today the TAM has become a coveted collector’s item, and in retrospect was the predecessor to later iMacs. It is an early Jony Ive product, one created before Jobs returned to Apple. VMM Blog:And a TAM Joins the Family

Apple eMate (Newton)

Shortly before the Newton’s demise Apple released the eMate, a small laptop (sub-notebook in modern parlance) designed for the education market. Colored Newton green, the eMate had a full QWERTY keyboard, a back-lit touch screen (stylus based), an expansion slot, AppleTalk networking capabilities, and a sturdy, appealing design. It ran the Newton OS, not Mac OS, and was a task-based portable computer well suited for note-taking, drawing, record keeping, etc.. The eMate was not a big commercial success, but its curvy shape, carrying handle and translucent plastics (another Jony Ive touch) influenced the designs of the colored iMacs and iBooks a few years later.

In the VMM the eMate is a perennial favorite. Many visitors to the Museum gravitate to this system, intuitively understand how to use it, and comment that it’s a cool little computer. Not bad for a vintage relic! VMM Blog:eMate Still a Crowd Favorite

Gemini iBook (Assistive Technology)

Touchscreen computers using a tablet form factor have been around for a long time, and work well as assistive technology devices used by the disabled. A decade before the iPad, a clamshell iBook G3 was married with a touchscreen to create this fully functional tablet Macintosh. The (now defunct) company Assistive Technology produced these systems back in 2001. The screen and keyboard of the iBook were replaced with an embedded touch sensitive display panel, and a small peripheral interface board along the top edge of the computer sports a USB port, a mini-joystick port, an input switch port, sound out and sound in ports. The iBook retains the ethernet port, modem, and CD-ROM drive. A popup keyboard (a la iOS) is used to type directly on screen, and speech recognition and speech synthesis software was included.

Cost of Gemini in 2001: $7500. Cost of iPad in 2014: $500. VMM Blog:Gemini iBook – a Mac OS 9 Tablet Mac

Axiotron Modbook

Six years after the Gemini iBook another company took a crack at making a tablet Mac, and this time for a wider audience. In 2007 Axiotron partnered with longtime Apple vendor OWC and introduced the Modbook, which took an Intel based MacBook and replaced the display with a touchscreen. Running OS X and offering a powerful computer in an elegant package, the Modbook defined the tablet Macintosh for several years – being, basically, the only entry.

In 2010 Apple introduced the iPad, and many predicted the Modbook’s demise. And indeed it did disappear for a few years, but reappeared in 2012 as the Modbook Pro, produced by a new company and using a 13″ MacBook Pro as the base system. There isn’t a large market for this kind of device, and it isn’t nearly as light or cheap as an iPad, but it’s still the only true OS X tablet in existence!

Apple Developer Transition System (Mac OS X Intel Migration)

In 2006 Apple stunned the world (again) by announcing they were going over to the Dark Side: the Macintosh was going to switch to Intel processors. Apple had been secretly compiling Mac OS X on Intel chips ever since it’s evolution from NeXTstep, and the G5 marked the end of the line for the PowerPC Macintosh. To allow developers to prepare their software for the change, Apple provided special Macs with Pentium-based motherboards inside PowerMac G5 cases for testing purposes. Called Developer Transition Systems (DTS), these Trojan horse “PowerMacs” came with a special developer version of Mac OS X 10.4.1 for Intel and were leased, not sold, to developers. The mothership required all DTS units to be returned after one year, so very few of these hybrid Macs survive outside the gates of Cupertino.

Memory Museum Mac Os X

This DTS is in working condition but does not have a copy of 10.4.1 for Intel. A previous owner had used the tower as a (shudder) Windows XP machine and erased the Apple development software. Noooooo!!!! If anyone has a copy of Mac OS X build 8b1025, please contact me. (Update: software has been located.)

Historical note: the leaking of this early Tiger on Intel release spawned the birth of the Hackintosh. VMM Blog:Apple DTS – a Trojan Horse PowerMac

While reading thru some Apple forums, I found a question people asked a lot. While most responses were generally correct, I felt that all answers lacked some important details and as a result confused people even more. The purpose of this article to clarify those details as much as possible.

First, let’s answer the first question from the title of the post.

What is wired memory?

Wired memory on Mac is reserved for the macOS kernel and its data structures, and it cannot be paged out. The normal size of the wired memory is around 2GB. User applications add on average 1MB per instance, and too many running programs can contribute to high wired memory usage.

Now, let’s dive into more technical details.

When the Mac suddenly becomes too slow, the laptop owners start browsing forums and learn to check the memory tab in Activity Monitor.

The screenshot above which I made after rebooting the Mac indicates that my Mac has 8GB of Physical Memory and 2.33GB of it is in the Used Memory bucket. The used memory then consists of App Memory (1.2GB) and Wired Memory (1.13GB).

Why do people ask about Wired memory?

Wired memory is a memory that can’t be compressed or paged out to your startup drives, so it must stay in RAM. Moreover, other processes can’t borrow it.

The key phrase here is “can’t be paged out.”

Before we proceed further let me explain what paging is.

The architecture of modern computers was designed in the 20th century. Any computer has three main parts: processor, RAM (random access memory) and storage (disk, tape, punched cards, etc.).

The processor works directly with RAM because the latter is thousands of times faster than HHD or SSD. Besides the speed, there are two more differences between RAM and HHD:

• RAM needs constant power. When a computer shuts down or restarts, the data in RAM gets wiped. Hard drives preserve data even when the computer is off.
• RAM is much more expensive. For instance, for an additional $200, you can buy either 8GB more RAM or 128GB more SSD when purchasing a new MacBook Pro.

The last point is significant. If RAM was cheap, then Apple would stuff its laptops with tons of memory, and nobody would care to read this article. But since its more expensive than disk storage computer engineers invented memory swapping or paging.

Let me use a whiteboard analogy.
Imagine, you work in a startup company which rents couple desks in a coworking space. Amenities in a coworking environment include unlimited coffee and beer, Wi-Fi, bike storage, and a whiteboard.

When Team A needs to brainstorm the Next Big Thing, they go to the whiteboard and start writing down some ideas. Unfortunately, there is only one whiteboard on the floor. Team B wants to brainstorm their TNBT too, and they also need some whiteboard space.

Team A graciously agrees to share some of the whiteboard space. Then another team comes, and another. With each team, the amount of free space shrinks.

When the available area gets too tight, teams decide to write down some of their ideas on the paper and clear the piece of the whiteboard for new ideas. When they need to access their old ideas, they search thru past papers and copy them to the whiteboard.

Memory management in modern operating systems works similarly. In this case, a whiteboard is a physical memory which is shared by apps (teams). When apps request additional memory, and there is no more free space, the OS checks all memory pages.

The OS tries to find ones that were not used recently and copies them to the disk. Apps do not write down unused memory like in whiteboard example, the OS does. When the app needs back that data, the OS reads it back to RAM from the disk.

In theory, more disk storage the computer has more RAM can be extended by paging. The reverse is also true, in case of little or no free disk space swapping is almost impossible.

This wonderful mechanism, however, has a significant flow: disk is thousands of times slower than RAM. When there is no enough memory, the system keeps paging in and out data continuously, which causes so-called disk thrashing.

In the latter case, the computer, instead of executing programs keeps moving data making the life of a computer user miserable.

So what it has to do with wired memory? Continuing the analogy, imaging the coworking administration decided to block the quarter of the whiteboard and write a schedule of events on it. Plus they disallowed any team to wipe off the schedule.

More space the administration takes less whiteboard space teams can use. More wired memory the macOS uses fewer memory apps can share.

By the way, if you were wondering what represents Cached Files in the first screenshot, it’s a memory that was used by an app which was recently terminated. It’s as if Team A decided to go to a nearby restaurant to grab some lunch.

If by the time they come back, their ideas are still on the whiteboard, they can start from where they left. If not, then they have to copy everything from their papers back to the whiteboard.

Cached Files is a mechanism which macOS uses to speed up the recently closed applications in case if a user wants to start them again. If meantime another app needs more memory, the OS will claim it from Cashed Files.

So, if you see too much Cached Files don’t worry, it’s same as free memory.

If you need proof, try following in Terminal:

• In the Terminal app type sudo purge and hit Enter
• Type in the admin password

When I ran this command, the only thing that has changed in Activity Monitor was Cached Files: its size dropped from 1.89GB to 594MB.

Is it ok to use sudo purge? There is no harm because all it does is clear unused memory. But it also doesn’t do anything valuable. macOS can release unused memory when apps ask for more.

What’s included in the Wired memory?

According to Apple documentation, wired memory is a part of memory reserved for OS kernel and its data structures. Following kernel objects belong to the wired memory: Virtual Memory objects, virtual memory and I/O buffer caches, various drivers.

User applications do not directly work with the hardware; they send requests to kernel drivers and those, in turn, perform hardware operations. For instance, the internet browser does not send pixels to the MacBook screen. Instead, it sends requests to the video driver, which then changes colors of pixels on the screen.

However, user apps can also influence how much of wired memory is used, although indirectly.

Following is a table with some (not all) types of objects user apps indirectly create in the wired memory. Note that the data in the table is outdated, but it at least gives some idea why the wired memory changes every time we load or unload an app.

Let me explain some of the objects in the table on the example of the Google Chrome browser. When I first started Chrome, it created several processes: one Google Chrome and 8 Google Chrome Helpers. The wired memory immediately jumped to 1.35GB.

Each line in the Activity Monitor is a process: an application instance. Each process is a collection of threads and threads perform actual work on the computer. If data in Table 1 was current, we could count that Google Chrome process added 16KB to store process data, plus 46 * 21KB = 966KB for threads.

Chrome is an interesting app. Every time you open a new tab, it starts additional helpers. Each helper is a separate process, and each process spawns numerous threads.

When I opened one tab, the number of Chrome helpers jumped from 8 to 16. After opening a second tab the number of helpers increased to 24, and after third to 26. After opening three tabs, the wired memory size increased to 1.61GB.

As you can see each process indirectly increases wired memory because macOS has to record those threads somewhere.

And this is not all. While Apple claims that wired memory is reserved for kernel and some objects which describe user processes, some applications can tap into the wired memory directly.

For instance, if you ever used virtualization software such as Parallels Desktop or VMWare, you should know that they use the wired memory directly to improve the performance.

If you think about this, it makes perfect sense. Virtual frameworks are designed to act like real machines so that OS running inside can handle the memory the way they always do. For instance, if you run macOS virtual machine on Mac, the macOS will create its version of wired memory inside VM.

After digging a bit in the Kernel Programming Guide, I found that applications can allocate memory in the kernel by calling kmem_alloc_wired function instead of regular alloc.

Now, what all of this means in practice?

How to free up memory on Mac

There are two main reasons for the high usage of wired memory:

1) Some applications modify the kernel and use wired memory deliberately. Examples are drivers and applications working on the kernel level such as antiviruses, or virtual machines. If for instance, there are some widgets in the Mission control, turn off those you don’t need.

Memory Museum Mac Os 11

In the case of virtual machines, the remedy is to limit the memory configuration. For example, if the Windows VM is configured to use 8GB of RAM lower it to 4GB.

Mac Os Download

2) When too many applications are active, they still use RAM. Unlike Windows, where clicking on close button unloads the app, in macOS, the app continues staying in memory. You can tell them by a little dot under the icon in the Dock.

Use Command and Q key combination to quit the app altogether. If some apps still stay in the memory rebooting the computer sometimes can fix the problem.

And finally, high wired memory usage is not always a sign of a problem. In the following example used memory was almost 31GB on a 32GB Mac, and wired memory accounted for the bulk of used (26.61GB).

However, look at the left side of the screenshot: Memory Pressure. Memory Pressure section in Activity Monitor can have one of 3 colors like a traffic light: green, yellow, and red. If memory pressure color is red, then more RAM is needed. In case if it’s green, then there is enough memory for the current load.

Wired memory does not get released immediately when an application quits. It gets cleared by a garbage collection process which may take some time, and during this time the wired memory size may be too high.

Resources:

Mac Os Mojave

Image credit: Flikr