Supported Operating Systems: OS X 10.13 (High Sierra), OS X 10.14 (Mojave), macOS Catalina (10.15). Only genuine versions of Mac Operating Systems are supported. CPU: Intel processor; RAM: 4GB or higher; Hard Drive: 1GB or higher available space. Shop for mac memory at Best Buy. Find low everyday prices and buy online for delivery or in-store pick-up. Show Operating System filter description. MacOS Catalina macOS Catalina. MacOS Catalina 10.15 macOS Catalina 10.15.

The simplest answer to the question: how much RAM do I need for my Mac is ‘as much as possible.’ You can never have too much RAM, whereas having too little can seriously affect the performance of your Mac. Sadly, however, it’s not quite as simple as that. Adding extra RAM, whether you do it when you buy your new Mac or you add it later, costs money, quite a lot of money. So the question of how much RAM to put in a new Mac is comes down to the balance between affordability and the additional benefit you’ll get from more RAM.

Why upgrade Mac RAM?

It used to be the case that adding more RAM would improve the performance of your Mac in almost every task. But computers have moved on since then. Better memory management, faster storage for caching files that can’t be stored in RAM, and blazing fast graphics processing units (GPUs) with their own dedicated RAM mean that the load on your main Mac RAM is less than it used to be.

Much of the work in generating frames for games, for example, is done by the GPU and its RAM. However, if you work with large images (bigger than, say, 100MB) or with huge databases or monster-sized spreadsheets, more RAM will be a huge benefit.

How to check your Mac's RAM usage

The quickest way to identify whether you need more memory is to check your Mac’s RAM usage.

One way to do that is to use the Manu App in CleanMyMac X. This feature will show you immediately how much free RAM you have and allows you to free up memory at the click of a button. It’s the easiest way to monitor and free up RAM. So, download the app (for free) and monitor your memory usage.

Alternatively, you can check the RAM usage manually:

  1. Go to your Applications folder.
  2. Open the Utilities folder and launch Activity Monitor.
  3. Click the Memory tab at the top and look at the Memory Pressure graph at the bottom of the screen.
  4. To the right of the graph, you’ll see a table. In that table, Physical Memory is the amount of RAM installed on your Mac.

Keep that window open while you work and check it now and again. If the graph stays green, there’s nothing to worry about and you don’t need more memory. If it’s green and yellow, there’s some pressure on your Mac’s RAM but it’s ok. If the graph is mostly red, however, it’s under serious pressure and your Mac’s startup drive is being used to store data that should be in RAM. This will slow down your Mac.

Just because the graph is in the red doesn’t mean you need to rush out and buy more RAM (assuming you have a Mac that can be upgraded), however. Closing browser tabs you’re not using will help, too. And you can free up memory by closing applications you’re not using or by logging out of accounts that aren’t in use, if you’re signed into more than one account.

To find out which apps, processes and browser tabs are using up the most RAM, click the down arrow at the top of the Memory column in Activity Monitor. That will order processes by how much RAM they’re using, allowing you to easily see who the culprits are. If you see any apps or web pages that are using lots of RAM and you don’t need, close them.

There are also third-party utilities that can report memory usage and ‘clean’ RAM when you close applications, so that the memory is freed up for use by other applications.

How can I upgrade Mac RAM?

Some Macs can be upgraded and some can’t. If you’ve bought a MacBook, MacBook Pro or MacBook Air in the last five years or so, you won’t be able to upgrade the memory in it. If you have an iMac, you may be able to perform a Mac RAM upgrade, depending on when it was made and whether it has free slots. You can find a complete list of which iMacs can be upgraded here.

Memory Optimizer Mac Os X

The iMac Pro’s memory can only be upgraded by Apple or an Authorised Service Provider. Both the Mac Pro and Mac mini can be upgraded.

How much RAM do I actually need?

So, after all that: how much RAM should you have fitted in a new Mac? For most users, 8GB is fine. You’ll be able to quite comfortably work on documents, edit photos and video and surf the web without any problems.

If you work on very large image files, databases, or spreadsheets, or if you really need to have lots of applications open at the same time, you might consider upgrading to 16GB. But you’d need to weigh the cost of the extra RAM against the benefit you’d notice.

What else can I do to improve my Mac’s performance?

The one and only reason for adding more RAM is to make your Mac run faster and more smoothly. However, there are other ways you can do this. Swapping a hard drive for an SSD, for example, won’t just boost startup times, but because macOS uses the startup drive to cache files, it will improve performance too.

Mac os x leopard

Also, freeing up space on your startup drive will help, particularly getting rid of files you don’t need and that clog up your system. The best way to do that is to use a tool like CleanMyMac X. CleanMyMac scans your Mac for files it thinks you no longer need. These include system junk, Photos files that can be safely removed, and Mail attachments that can be re-downloaded if you ever need them again, and much more. By the way, the app is free to download, so give it a try!

As you can see, deciding how much RAM you need for your Mac isn’t straightforward. There are lots of things to consider. However, adding more RAM isn’t the guaranteed performance boost it used to be. For most people, the base 8GB that ships with current Macs is enough. If you do think your Mac could do with a performance boost, try the techniques described above before you rush out and buy more RAM.

These might also interest you:

(Redirected from Mac OS memory management)
'About This Computer' Mac OS 9.1 window showing the memory consumption of each open application and the system software itself.

Historically, the classic Mac OS used a form of memory management that has fallen out of favor in modern systems. Criticism of this approach was one of the key areas addressed by the change to Mac OS X.

The original problem for the engineers of the Macintosh was how to make optimum use of the 128 KB of RAM with which the machine was equipped, on Motorola 68000-based computer hardware that did not support virtual memory.[1] Since at that time the machine could only run one application program at a time, and there was no fixedsecondary storage, the engineers implemented a simple scheme which worked well with those particular constraints. That design choice did not scale well with the development of the machine, creating various difficulties for both programmers and users.


The primary concern of the original engineers appears to have been fragmentation - that is, the repeated allocation and deallocation of memory through pointers leading to many small isolated areas of memory which cannot be used because they are too small, even though the total free memory may be sufficient to satisfy a particular request for memory. To solve this, Apple engineers used the concept of a relocatable handle, a reference to memory which allowed the actual data referred to be moved without invalidating the handle. Apple's scheme was simple - a handle was simply a pointer into a (non relocatable) table of further pointers, which in turn pointed to the data.[2]If a memory request required compaction of memory, this was done and the table, called the master pointer block, was updated. The machine itself implemented two areas in memory available for this scheme - the system heap (used for the OS), and the application heap.[3]As long as only one application at a time was run, the system worked well. Since the entire application heap was dissolved when the application quit, fragmentation was minimized.

The memory management system had weaknesses; the system heap was not protected from errant applications, as would have been possible if the system architecture had supported memory protection, and this was frequently the cause of system problems and crashes.[4]In addition, the handle-based approach also opened up a source of programming errors, where pointers to data within such relocatable blocks could not be guaranteed to remain valid across calls that might cause memory to move. This was a real problem for almost every system API that existed. Because of the transparency of system-owned data structures at the time, the APIs could do little to solve this. Thus the onus was on the programmer not to create such pointers, or at least manage them very carefully by dereferencing all handles after every such API call. Since many programmers were not generally familiar with this approach, early Mac programs suffered frequently from faults arising from this.[5]

Palm OS and 16-bit Windows use a similar scheme for memory management, but the Palm and Windows versions make programmer error more difficult. For instance, in Mac OS, to convert a handle to a pointer, a program just de-references the handle directly, but if the handle is not locked, the pointer can become invalid quickly. Calls to lock and unlock handles are not balanced; ten calls to HLock are undone by a single call to HUnlock.[6] In Palm OS and Windows, handles are an opaque type and must be de-referenced with MemHandleLock on Palm OS or Global/LocalLock on Windows. When a Palm or Windows application is finished with a handle, it calls MemHandleUnlock or Global/LocalUnlock. Palm OS and Windows keep a lock count for blocks; after three calls to MemHandleLock, a block will only become unlocked after three calls to MemHandleUnlock.

Addressing the problem of nested locks and unlocks can be straightforward (although tedious) by employing various methods, but these intrude upon the readability of the associated code block and require awareness and discipline on the part of the coder.

Memory leaks and stale references[edit]

Awareness and discipline are also necessary to avoid memory 'leaks' (failure to deallocate within the scope of the allocation) and to avoid references to stale handles after release (which usually resulted in a hard crash—annoying on a single-tasking system, potentially disastrous if other programs are running).


The situation worsened with the advent of Switcher, which was a way for a Mac with 512KB or more of memory to run multiple applications at once.[7] This was a necessary step forward for users, who found the one-app-at-a-time approach very limiting. Because Apple was now committed to its memory management model, as well as compatibility with existing applications, it was forced to adopt a scheme where each application was allocated its own heap from the available RAM.[8]The amount of actual RAM allocated to each heap was set by a value coded into the metadata of each application, set by the programmer. Sometimes this value wasn't enough for particular kinds of work, so the value setting had to be exposed to the user to allow them to tweak the heap size to suit their own requirements. While popular among 'power users', this exposure of a technical implementation detail was against the grain of the Mac user philosophy. Apart from exposing users to esoteric technicalities, it was inefficient, since an application would be made to grab all of its allotted RAM, even if it left most of it subsequently unused. Another application might be memory starved, but would be unable to utilize the free memory 'owned' by another application.[3]

While an application could not beneficially utilize a sister application's heap, it could certainly destroy it, typically by inadvertently writing to a nonsense address. An application accidentally treating a fragment of text or image, or an unassigned location as a pointer could easily overwrite the code or data of other applications or even the OS, leaving 'lurkers' even after the program was exited. Such problems could be extremely difficult to analyze and correct.

Switcher evolved into MultiFinder in System 4.2, which became the Process Manager in System 7, and by then the scheme was long entrenched. Apple made some attempts to work around the obvious limitations – temporary memory was one, where an application could 'borrow' free RAM that lay outside of its heap for short periods, but this was unpopular with programmers so it largely failed to solve the problems. Apple's System 7 Tune-up addon added a 'minimum' memory size and a 'preferred' size—if the preferred amount of memory was not available, the program could launch in the minimum space, possibly with reduced functionality. This was incorporated into the standard OS starting with System 7.1, but still didn't address the root problem.[9]

Virtual memory schemes, which made more memory available by paging unused portions of memory to disk, were made available by third-party utilities like Connectix Virtual, and then by Apple in System 7. This increased Macintosh memory capacity at a performance cost, but did not add protected memory or prevent the memory manager's heap compaction that would invalidate some pointers.

32-bit clean[edit]

Originally the Macintosh had 128 kB of RAM, with a limit of 512 kB. This was increased to 4 MB upon the introduction of the Macintosh Plus. These Macintosh computers used the 68000 CPU, a 32-bit processor, but only had 24 physical address lines. The 24 lines allowed the processor to address up to 16 MB of memory (224 bytes), which was seen as a sufficient amount at the time. The RAM limit in the Macintosh design was 4 MB of RAM and 4 MB of ROM, because of the structure of the memory map.[10] This was fixed by changing the memory map with the Macintosh II and the Macintosh Portable, allowing up to 8 MB of RAM.

Because memory was a scarce resource, the authors of the Mac OS decided to take advantage of the unused byte in each address. The original Memory Manager (up until the advent of System 7) placed flags in the high 8 bits of each 32-bit pointer and handle. Each address contained flags such as 'locked', 'purgeable', or 'resource', which were stored in the master pointer table. When used as an actual address, these flags were masked off and ignored by the CPU.[4]

While a good use of very limited RAM space, this design caused problems when Apple introduced the Macintosh II, which used the 32-bit Motorola 68020 CPU. The 68020 had 32 physical address lines which could address up to 4 GB (232 bytes) of memory. The flags that the Memory Manager stored in the high byte of each pointer and handle were significant now, and could lead to addressing errors.

In theory, the architects of the Macintosh system software were free to change the 'flags in the high byte' scheme to avoid this problem, and they did. For example, on the Macintosh IIci and later machines, HLock() and other APIs was rewritten to implement handle locking in a way other than flagging the high bits of handles. But, many Macintosh application programmers and a great deal of the Macintosh system software code itself accessed the flags directly rather than using the APIs, such as HLock(), which had been provided to manipulate them. By doing this they rendered their applications incompatible with true 32-bit addressing, and this became known as not being '32-bit clean'.

In order to stop continual system crashes caused by this issue, System 6 and earlier running on a 68020 or a 68030 would force the machine into 24-bit mode, and would only recognize and address the first 8 megabytes of RAM, an obvious flaw in machines whose hardware was wired to accept up to 128 MB RAM – and whose product literature advertised this capability. With System 7, the Mac system software was finally made 32-bit clean, but there were still the problem of dirty ROMs. The problem was that the decision to use 24-bit or 32-bit addressing has to be made very early in the boot process, when the ROM routines initialized the Memory Manager to set up a basic Mac environment where NuBus ROMs and disk drivers are loaded and executed. Older ROMs did not have any 32-bit Memory Manager support and so was not possible to boot into 32-bit mode. Surprisingly, the first solution to this flaw was published by software utility company Connectix, whose 1991 product MODE32 reinitialized the Memory Manager and repeated early parts of the Mac boot process, allowing the system to boot into 32-bit mode and enabling the use of all the RAM in the machine. Apple licensed the software from Connectix later in 1991 and distributed it for free. The Macintosh IIci and later Motorola based Macintosh computers had 32-bit clean ROMs.

It was quite a while before applications were updated to remove all 24-bit dependencies, and System 7 provided a way to switch back to 24-bit mode if application incompatibilities were found.[3] By the time of migration to the PowerPC and System 7.1.2, 32-bit cleanliness was mandatory for creating native applications and even later Motorola 68040 based Macs could not support 24-bit mode.[6][11]

Object orientation[edit]

The rise of object-oriented languages for programming the Mac – first Object Pascal, then later C++ – also caused problems for the memory model adopted. At first, it would seem natural that objects would be implemented via handles, to gain the advantage of being relocatable. These languages, as they were originally designed, used pointers for objects, which would lead to fragmentation issues. A solution, implemented by the THINK (later Symantec) compilers, was to use Handles internally for objects, but use a pointer syntax to access them. This seemed a good idea at first, but soon deep problems emerged, since programmers could not tell whether they were dealing with a relocatable or fixed block, and so had no way to know whether to take on the task of locking objects or not. Needless to say this led to huge numbers of bugs and problems with these early object implementations. Later compilers did not attempt to do this, but used real pointers, often implementing their own memory allocation schemes to work around the Mac OS memory model.

Prime reading offers hundreds of free ebooks, magazines, and more. Kindle Unlimited, which is a subscription-based service, lets you read about a million titles (including magazines and newspapers) for a monthly price.Kindle on the Mac has plenty of customization features, too. Torrent bookreader for mac high sierra. You can also add highlights and notes. You can change the theme to white, sepia, or black, and adjust the font size and style to tailor your reading experience. It is especially beneficial to Prime subscribers.

While the Mac OS memory model, with all its inherent problems, remained this way right through to Mac OS 9, due to severe application compatibility constraints, the increasing availability of cheap RAM meant that by and large most users could upgrade their way out of a corner. The memory wasn't used efficiently, but it was abundant enough that the issue never became critical. This is ironic given that the purpose of the original design was to maximise the use of very limited amounts of memory. Mac OS X finally did away with the whole scheme, implementing a modern sparse virtual memory scheme. A subset of the older memory model APIs still exist for compatibility as part of Carbon, but map to the modern memory manager (a threadsafe malloc implementation) underneath.[6]Apple recommends that Mac OS X code use malloc and free 'almost exclusively'.[12]

Memory Usage For Mac Os X


  1. ^Hertzfeld, Andy (September 1983), The Original Macintosh: We're Not Hackers!, retrieved 2010-05-10
  2. ^Hertzfeld, Andy (January 1982), The Original Macintosh: Hungarian, archived from the original on 2010-06-19, retrieved 2010-05-10
  3. ^ (2000-12-15), Memory management in Mac OS, archived from the original on 2010-05-16, retrieved 2010-05-10
  4. ^ abHertzfeld, Andy, The Original Macintosh: Mea Culpa, retrieved 2010-05-10
  5. ^Apple Computer (1985-10-01), Technical Note OV09: Debugging With PurgeMem and CompactMem, retrieved 2010-05-10
  6. ^ abcLegacy Memory Manager Reference, Apple Inc, 2007-06-27, retrieved 2010-05-10
  7. ^Hertzfeld, Andy (October 1984), The Original Macintosh: Switcher, retrieved 2010-05-10
  8. ^Mindfire Solutions (2002-03-06), Memory Management in Mac OS(PDF), p. 2, retrieved 2010-05-10
  9. ^'System 7.1 upgrade guide'(PDF). Archived from the original(PDF) on 2016-03-04. Retrieved 2015-05-26.
  10. ^'memory maps'. 2001-03-28. Retrieved 2010-05-11.
  11. ^Apple Computer (1991-01-01), Technical Note ME13: Memory Manager Compatibility, retrieved 2010-05-10
  12. ^Memory Allocation Recommendations on OS X, Apple Inc, 2005-07-12, retrieved 2009-09-22

External links[edit]

  • Macintosh: ROM Size for Various Models, Apple Inc, 2000-08-23, retrieved 2009-09-22
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