When you look at the work station of a guy like me, you see LOT'S of different tools and gadgets. This is a very sophisticated profession that requires skilled, knowledgeable hands and minds.While most clocks differ in service requirements, basic principles apply to all. When a clock is in need of cleaning, the movement must be completely dismantled for proper servicing. Bearings in the movement must be refinished, and wear that has developed from dirty oil and rough bearings must be corrected in order for your clock to behave like it's new again. I provide everything from routine maintenance to complete overhaulsto insure your timepiece will operate as it's meant to for the greatest number of years possible.I do it RIGHT.....and my work is ALWAYS guaranteed !Grandfather clocks, like any other clock, need periodic maintenance to keep them in good running order. It is my recommendation that most newer clocks will need to be cleaned every 15 years on average. Older or antique clocks may run much longer but should still be cleaned at 20 year intervals. Even the best modern oils will be breaking down by then.Depending on operating conditions, a service call to oil the movement may be needed in the interim. Normally this would be no sooner than 7-10 years. Oiling the mechanism when it isn't called for can be just as detrimental to the movement as no oil at all. The right type of oil must be used, as oil properties vary widely depending on the application.Some symptoms that might be noticed if your clock is in need of these type services would be:Random stopping, may be able to restart.Sluggish tempo of the chime or strike. Timekeeping may become erratic or you may not be able to regulate it within the adjustment limits of the pendulum.Grandfather clocks are the pride of every home. Entrusting their repair to someone that doesn't have the proper qualifications can greatly increase the cost to put things right again. Without sounding egomaniacal....I am an expert with Grandfather Clocks.Wall and Mantel clocks have recommended service intervals for most new wall/mantel clocks, every 10 years for cleaning. No interim lubrication should be needed if the proper oil has been used to start with.Antique clocks should be cleaned every 15 years.Wall and mantel clocks require more frequent service than a grandfather clock because of the increased operating speed. Whereas a grandfather clock may only beat seconds in its escapement action(60 times per minute), their smaller cousins may beat 150 times per minute or more depending on the movement. Gears turn more frequently, and bearing wear develops more quickly as a result.I have extensive knowledge and experience working with these types of clocks.Anniversary clocks(so named because most are designed to run 400 days on a wind) require specialized knowledge for proper repair. Many of these fine timepieces have been lost due to repair inexperience. Arguably some of the most visually interesting clocks, they can be just as reliable a timekeeper as any other mechanical clock in your home. Because these clocks are normally operated under a glass dome or cover, they are much less susceptible to the ill effect of dust and other contaminants' that can creep into the mechanism area of most clocks. Recommended cleaning interval would be 15-20 years in most cases. Bearing wear is almost never present due to the slow movement action. The thin suspension wire that the pendulum hangs from is the leading cause of failure. It is only a few thousandths of an inch in thickness and doesn't take kindly to mishandling. However, by following 4 simple steps in setting up the clock, there is no reason the wire won't outlast you! My years of experience and the knowledge I acquired in the repair of these clocks make me the right choice when your’s needs help. Again...ANY type of clock or watch..........I'm your guy !Cuckoo and Nautical clocks have their beginnings traced back to Germany's Black Forest region. Cuckoo clocks have delighted owners with their whimsical sounds and original cosmetics and design. Because of the many case openings, cuckoo clocks will normally require cleaning every 7 years. Operating environment is a strong variable here as the mechanism can be subjected to even greater contamination if the clock is hung near an air vent for example.The most common errors in repair are made when attempting to readjust the linkages for clock animation when it is incorrectly disassembled. Separate music movements make for an even greater challenge to those not well versed in their repair and adjustment. I have worked on HUNDREDS of these clocks !!Nautical clocks on the other hand, have a nearly airtight casing that prevents frequent service requirements that would result from contamination of a high beat rate mechanism that is virtually standard on these clocks. Service of these clocks and the jeweled escapement that allows for their high degree of precision, requires an equally high degree of craftsmanship. With the price of such clocks reaching well over a thousand dollars in many instances, the skill level needed for correct repair is usually quite demanding. Again....I'm your guy. You can trust me with your valued possession.You can expect normal cleaning intervals for this type of clock to be in the 10-15 year range. RARE and UNUSUAL clocks. Due to the wide variety of designs encompassed here, the correct intervals for servicing can only be covered by direct communication. Please give me a call or send an email of what you have and I will be pleased to advise you of what is needed and when.The knowledge, skill and precision required to repair clocks of this category cannot be understated. The collectible value of such clocks keeps rising and so they are not only a treasured family heirloom but an appreciating investment as well. But the value in dollars is nothing compared to the sentimental value that can be contained in any clock I service. That has no measure by me, only you. I am acutely aware of this, that is why I utilize only the best suited materials, applied with the techniques and knowledge my many years in the craft have provided me. My goal is the same as yours. To keep your clock running for generations to come. WATCHES. Cell phones, computers, ovens, cable boxes and TV's all have the ability to keep you aware of the time. But, if you are like me or my wife and millions of others out there, there's still nothing like having that favorite watch proudly displayed on your arm. It may be old . It may be worn. It may be 'laughable' to some. But not to YOU. It's YOUR watch and it has sentimental value perhaps. Is it sitting in a box or a drawer...not working ? It doesn't have to be.Just gimme a call....and let's get it back on your WRIST...where it belongs !!If it ticks, clicks, cuckoos or tells time...I would love the opportunity to keep it running or repair it if need be.In some cases...I will come to you. In some cases, you will come to me. Either way...you'll be very pleased with my services, prices and turn around time.Just call me or email me.......and let's get the process started.Again...I look forward to EXCEEDING your expectations !!!!

1969 Ford Mustang Mach 1 Clock Converted to Quartz. 1947 Chevy Clock. 1964 Chevy Corvette Clock. 1955 Ford Thunderbird Clock. 40 Cadillac Lasalle Clock Before and After Restoration. 1965 Ford Thunderbird Clock with Quartz Conversion. Injection molded from high impact styrene and features a real glass lens for durability and scratch resistance. Quality American made Quartz clock movement for accuracy which will.

Add clocks with geared or free-moving hands. Set the time and run a live clock with a second hand. Display equivalent digital time. Add minute and hour hand labels. Jump the minute hand on geared clocks by intervals 1-60. Use the elapsed time tool to solve problems involving intervals of time. Overlay and shade circle fractions to. Classic Industries offers a wide selection of 1969 Ford Mustang parts, including 1969 Ford Mustang interior parts and soft trim, 1969 Ford Mustang exterior sheet metal, 1969 Ford Mustang moldings, 1969 Ford Mustang emblems, 1969 Ford Mustang weatherstrip and unique accessories, to nearly every nut and bolt needed for installation. Mach Clock Mach Clock is the live Clock for your Dock and Desktop! Featuring 8 different analog and digital faces, five different World Clocks, optionally show seconds, A.M/P.M. And flash the time separators; Mach Clock fits like a glove for your Mac, no matter what your style is!

The best way to describe the services page of this website, is to simply say: If it is a watch or a clock of any kind, chances are I can fix it. Whether it's routine maintenance of a Grandfather clock, or figuring out why your favorite Timex watch has stopped....you've come to the solution...Mack's Clock Repair !
©2017 A Rob McCreery Business Solutions Website. Want one ? Want it QUICKLY ? Don't want to pay a lot ? Click HERE !
EXPERT Clock and Watch repair for Pittsburgh, Altoona,Johnstown,Indiana,Pa !

The fundamental services and primitives ofthe OS X kernel are based on Mach3.0. Apple has modified and extended Mach to better meet OS X functional and performance goals.

Mach 3.0 was originally conceived as a simple, extensible,communications microkernel. It iscapable of running as a stand–alone kernel, with other traditionaloperating-system services such as I/O, file systems, and networkingstacks running as user-mode servers.

Mach 1 clock

However, in OS X, Mach is linked with other kernel componentsinto a single kernel address space. This is primarily for performance;it is much faster to make a direct call between linked componentsthan it is to send messages or do remote procedure calls (RPC) betweenseparate tasks. This modular structure results in a more robustand extensible system than a monolithic kernel would allow, withoutthe performance penalty of a pure microkernel.

Thus in OS X, Mach is not primarily a communication hubbetween clients and servers. Instead, its value consists of itsabstractions, its extensibility, and its flexibility. In particular,Mach provides

  • object-basedAPIs with communication channels (for example, ports) as object references

  • highly parallel execution, including preemptively scheduled threads and support for SMP

  • a flexible scheduling framework, with support for real-time usage

  • a complete set of IPC primitives, including messaging, RPC, synchronization, and notification

  • support for large virtual address spaces, shared memoryregions, and memory objects backed by persistent store

  • proven extensibility and portability, for example across instructionset architectures and in distributed environments

  • security and resource management as a fundamental principleof design; all resources are virtualized

Mach Kernel Abstractions

Mach provides a small set of abstractions that have been designedto be both simple and powerful. These are the main kernel abstractions:

  • Tasks. Theunits of resource ownership; each task consists of a virtual addressspace, a portrightnamespace, and one or more threads.(Similar to a process.)

  • Threads. The units of CPU execution withina task.

  • Addressspace. In conjunction with memory managers, Mach implementsthe notion of a sparse virtual address space and shared memory.

  • Memoryobjects. The internal units of memory management. Memoryobjects include named entries and regions; they are representationsof potentially persistent data that may be mapped into address spaces.

  • Ports.Secure, simplex communication channels, accessible only via sendand receive capabilities (known as port rights).

  • IPC.Message queues, remote procedure calls, notifications, semaphores,and lock sets.

  • Time.Clocks, timers, and waiting.

At the trap level, the interface to most Mach abstractionsconsists of messages sent to and from kernel ports representingthose objects. The trap-level interfaces (such as mach_msg_overwrite_trap)and message formats are themselves abstracted in normal usage bythe Mach Interface Generator(MIG).MIG is used to compile procedural interfaces to the message-basedAPIs, based on descriptions of those APIs.

Tasks and Threads

OS X processes and POSIXthreads (pthreads)are implemented on top of Mach tasks and threads, respectively.A thread is a point of control flow in a task. A task exists to provideresources for the threads it contains. This split is made to providefor parallelism and resource sharing.

A thread

  • is a pointof control flow in a task.

  • has access to all of the elements of the containing task.

  • executes (potentially) in parallel with other threads, eventhreads within the same task.

  • has minimal state information for low overhead.

A task

  • is a collectionof system resources. These resources, with the exception of theaddress space, are referenced by ports. These resources may be sharedwith other tasks if rights to the ports are so distributed.

  • provides a large, potentially sparse address space, referencedby virtual address. Portions of this space may be shared throughinheritance or external memory management.

  • contains some number of threads.

Note that a task has no life of its own—only threads executeinstructions. When it is said that “task Y does X,” what isreally meant is that “a thread contained within task Y does X.”

A task is a fairly expensive entity. It exists to be a collectionof resources. All of the threads in a task share everything. Twotasks share nothing without an explicit action (although the actionis often simple) and some resources (such as port receive rights) cannotbe shared between two tasks at all.

A thread is a fairly lightweight entity. It is fairly cheapto create and has low overhead to operate. This is true becausea thread has little state information (mostly its register state). Itsowning task bears the burdenof resource management. On a multiprocessor computer, it is possiblefor multiple threads in a task to execute in parallel. Even whenparallelism is not the goal, multiple threads have an advantagein that each threadcan use a synchronous programming style, instead of attempting asynchronousprogramming with a single thread attempting to provide multipleservices.

A threadis the basic computational entity. A thread belongs to one and onlyone task that defines its virtual address space. To affect the structureof the address space or to reference any resource other than theaddress space, the thread must execute a special trap instructionthat causes the kernel to perform operations on behalf of the threador to send a message to some agent on behalf of the thread. In general,these traps manipulate resources associated with the task containingthe thread. Requests can be made of the kernel to manipulate theseentities: to create them, delete them, and affect their state.

Mach provides a flexible framework for thread–schedulingpolicies. Early versions of OS X support both time-sharing and fixed-priority policies.A time-sharing thread’s priority is raised and lowered to balanceits resource consumption against other time-sharing threads.

Fixed-priority threads execute for a certain quantum of time, and then areput at the end of the queue of threads of equal priority. Settinga fixed priority thread’s quantum level to infinity allows thethread to run until it blocks, or until it is preempted by a threadof higher priority. High priority real-time threads are usuallyfixed priority.

Match Clock Game

OS X also provides time constraint scheduling for real-timeperformance. This scheduling allows you to specify that your threadmust get a certain time quantum within a certain period of time.

Mach scheduling is described further in Mach Scheduling and Thread Interfaces.

Ports, Port Rights, Port Sets,and Port Namespaces

With the exception of the task’s virtual address space,all other Mach resources are accessed through a level of indirectionknown as a port.A port is an endpoint of a unidirectional communication channelbetween a client who requests a service and a server who providesthe service. If a reply is to be provided to such a service request,a second port must be used. This is comparable to a (unidirectional)pipe in UNIX parlance.

In most cases, the resource that is accessed by the port (thatis, named by it) is referred to as an object. Most objects namedby a port have a single receiver and (potentially) multiple senders.That is, there is exactly one receive port, and at least one sendingport, for a typical object such as a message queue.

The service to be provided by an object is determined by themanager that receives the request sent to the object. It followsthat the kernel is the receiver for ports associated with kernel-providedobjects and that the receiver for ports associated with task-provided objectsis the task providing those objects.

For ports that name task-provided objects, it is possibleto change the receiver of requests for that port to a differenttask, for example by passing the port to that task in a message. Asingle task may have multiple ports that refer to resources it supports.For that matter, any given entity can have multiple ports that representit, each implying different sets of permissible operations. Forexample, many objects have a name port anda controlport (sometimes called the privileged port).Access to the control port allows the object to be manipulated;access to the name port simply names the object so that you canobtain information about it or perform other non-privileged operationsagainst it.

Tasks have permissions to access ports in certain ways (send,receive, send-once); these are called port rights. A port can be accessed only via a right. Ports are often usedto grant clients access to objects within Mach. Having the rightto send to the object’s IPC port denotes the right to manipulatethe object in prescribed ways. As such, port right ownership isthe fundamental security mechanismwithin Mach. Having a right to an object is to have a capabilityto access or manipulate that object.

Port rights can be copied and moved between tasks via IPC. Doing so,in effect, passes capabilities to some object or server.

One type of object referred to by a port is a port set.As the name suggests, a port set is a set of port rights that canbe treated as a single unit when receiving a message or event fromany of the members of the set. Port sets permit one thread to waiton a number of message and event sources, for example in work loops.

Traditionally in Mach, the communication channel denoted bya port was always a queue of messages.However, OS X supports additional types of communication channels, andthese new types of IPC object are also represented by ports andport rights. See the section Interprocess Communication (IPC),for more details about messages and other IPC types.

Ports and port rights do not have systemwide names that allowarbitrary ports or rights to be manipulated directly. Ports canbe manipulated by a task only if the task has a port right in itsport namespace. A port right is specified by a port name, an integerindex into a 32-bit portnamespace. Each task has associated with it a single port namespace.

Tasks acquire port rights when another task explicitly insertsthem into its namespace, when they receive rights in messages, bycreating objects that return a right to the object, and via Machcalls for certain special ports (mach_thread_self, mach_task_self,and mach_reply_port.)

Memory Management

As with most modern operating systems, Mach provides addressingto large, sparse, virtual address spaces. Runtime access is madevia virtual addresses that may not correspond to locations in physicalmemory at the initial time of the attempted access. Mach is responsiblefor taking a requested virtual address and assigning it a correspondinglocation in physical memory. It does so through demand paging.

A range of a virtual address space is populated with datawhen a memory object is mapped into that range. All data in an addressspace is ultimately provided through memory objects. Mach asks theowner of a memory object (apager)for the contents of a page when establishing it in physical memoryand returns the possibly modified data to the pager before reclaimingthe page. OS X includes two built-in pagers—the defaultpager and the vnode pager.

The default pager handles nonpersistent memory, known as anonymousmemory. Anonymous memory is zero-initialized, and it existsonly during the life of a task. The vnode pager maps files intomemory objects. Mach exports an interface to memory objects to allowtheir contents to be contributed by user-mode tasks. This interfaceis known as the External Memory Management Interface, or EMMI.

The memory management subsystem exports virtual memory handlesknown as named entries or namedmemory entries. Like most kernel resources, these aredenoted by ports. Having a named memory entry handle allows theowner to map the underlying virtual memory object or to pass theright to map the underlying object to others. Mapping a named entryin two different tasks results in a shared memory window betweenthe two tasks, thus providing a flexible method for establishingshared memory.

Beginning in OS X v10.1, the EMMI systemwas enhanced to support “portless” EMMI. In traditional EMMI,two Mach ports were created for each memory region, and likewise twoports for each cached vnode. Portless EMMI, in its initial implementation,replaces this with direct memory references (basically pointers).In a future release, ports will be used for communication with pagersoutside the kernel, while using direct references for communicationwith pagers that reside in kernel space. The net result of thesechanges is that early versions of portless EMMI do not support pagersrunning outside of kernel space. This support is expected to bereinstated in a future release.

Address ranges of virtual memory space may also be populatedthrough direct allocation (using vm_allocate).The underlying virtual memory object is anonymous and backed by thedefault pager. Shared ranges of an address space may also be setup via inheritance. When new tasks are created, they are clonedfrom a parent. This cloning pertains to the underlying memory addressspace as well. Mapped portions of objects may be inherited as acopy, or as shared, or not at all, based on attributes associatedwith the mappings. Mach practices a form of delayed copy known as copy-on-write tooptimize the performance of inherited copies on task creation.

Clock Match

Rather than directly copying the range, a copy-on-write optimization is accomplishedby protected sharing. The two tasks share the memory to be copied,but with read-only access. When either task attempts to modify aportion of the range, that portion is copied at that time. Thislazy evaluation of memory copies is an important optimization thatpermits simplifications in several areas, notably the messaging APIs.

One other form of sharing is provided by Mach, through theexport of namedregions. A named region is a form of a named entry, butinstead of being backed by a virtual memory object, it is backedby a virtual map fragment. This fragment may hold mappings to numerousvirtual memory objects. It is mappable into other virtual maps,providing a way of inheriting not only a group of virtual memoryobjects but also their existing mapping relationships. This featureoffers significant optimization in task setup, for example when sharinga complex region of the address space used for shared libraries.

Interprocess Communication(IPC)

Communication between tasks is an important element of theMach philosophy. Mach supports a client/server system structurein which tasks (clients) access services by making requests of othertasks (servers) via messages sent over a communication channel.

The endpoints of these communication channels in Mach arecalled ports, while port rights denote permission to use the channel.The forms of IPC provided by Mach include

  • messagequeues

  • semaphores

  • notifications

  • lock sets

  • remote procedure calls (RPCs)

The type of IPC object denoted by the port determines theoperations permissible on that port, and how (and whether) datatransfer occurs.

Important: The IPCfacilities in OS X are in a state of transition. In early versionsof the system, not all of these IPC types may be implemented.

Time Clock Machine

There are two fundamentally different Mach APIs for raw manipulationof ports—the mach_ipc familyand the mach_msg family.Within reason, both families may be used with any IPC object; however,the mach_ipc calls arepreferred in new code. The mach_ipc calls maintainstate information where appropriate in order to support the notionof a transaction. The mach_msg callsare supported for legacy code but deprecated; they are stateless.

IPC Transactions and EventDispatching

When a thread calls mach_ipc_dispatch,it repeatedly processes events coming in on the registered portset. These events could be an argument block from an RPCobject (as the results of a client’s call), a lock object beingtaken (as a result of some other thread’s releasing the lock),a notification or semaphore being posted, or a message coming infrom a traditional message queue.

Match Clocks

These events are handled via callouts from mach_msg_dispatch.Some events imply a transaction during the lifetime of the callout.In the case of a lock, the state is the ownership of the lock. Whenthe callout returns, the lock is released. In the case of remoteprocedure calls, the state is the client’s identity, the argumentblock, and the reply port. When the callout returns, the reply issent.

When the callout returns, the transaction (if any) is completed,and the thread waits for the next event. The mach_ipc_dispatch facilityis intended to support work loops.

Message Queues

Originally, the sole style of interprocess communication inMach was the messagequeue. Only one task can hold the receive right for a port denotinga message queue. This one task is allowed to receive (read) messagesfrom the port queue. Multiple tasks can hold rights to the portthat allow them to send (write) messages into the queue.

A task communicates with another task by building a data structurethat contains a set of data elements and then performing a message-sendoperation on a port for which it holds send rights. At some latertime, the task with receive rights to that port will perform a message-receiveoperation.

A message may consist of some or all of the following:

  • pure data

  • copies of memory ranges

  • port rights

  • kernel implicit attributes, such as the sender’s security token

The message transfer is an asynchronous operation. The messageis logically copied into the receiving task, possibly with copy-on-writeoptimizations. Multiple threads within the receiving task can beattempting to receive messages from a given port, but only one thread canreceive any given message.

March Clock Change

Semaphores

Semaphore IPC objects support wait, post, and post all operations.These are counting semaphores, in that posts are saved (counted)if there are no threads currently waiting in that semaphore’swait queue. A post all operation wakes up all currently waitingthreads.

Notifications

Like semaphores, notification objects also support post andwait operations, but with the addition of a state field. The stateis a fixed-size, fixed-format field that is defined when the notificationobject is created. Each post updates the state field; there is asingle state that is overwritten by each post.

Locks

A lock is an object that provides mutually exclusive accessto a critical section. The primary interfaces to locks are transactionoriented (see IPC Transactions and Event Dispatching). During the transaction,the thread holds the lock. When it returns from the transaction,the lock is released.

Remote Procedure Call (RPC) Objects

March Clocks Ahead

As the name implies, an RPC object is designed to facilitateand optimize remote procedure calls. The primary interfaces to RPCobjects are transaction oriented (see IPC Transactions and Event Dispatching)

When an RPC object is created, a set of argument block formatsis defined. When an RPC (a send on the object) is made by a client,it causes a message in one of the predefined formats to be createdand queued on the object, then eventually passed to the server (the receiver).When the server returns from the transaction, the reply is returnedto the sender. Mach tries to optimize the transaction by executingthe server using the client’s resources; this is called threadmigration.

Time Management

The traditional abstraction of time in Mach is the clock, which provides a setof asynchronous alarm services based on mach_timespec_t.There are one or more clock objects, each defining a monotonicallyincreasing time value expressed in nanoseconds. The real-time clockis built in, and is the most important, but there may be other clocksfor other notions of time in the system. Clocks support operationsto get the current time, sleep for a given period, set an alarm(a notification that is sent at a given time), and so forth.

The mach_timespec_t API is deprecatedin OS X. The newer and preferred API is based on timer objectsthat in turn use AbsoluteTime asthe basic data type. AbsoluteTime isa machine-dependent type, typically based on the platform-nativetime base. Routines are provided to convert AbsoluteTime valuesto and from other data types, such as nanoseconds. Timer objectssupport asynchronous, drift-free notification, cancellation, andpremature alarms. They are more efficient and permit higher resolutionthan clocks.


Mach Clock_sleep


Copyright © 2002, 2013 Apple Inc. All Rights Reserved. Terms of Use Privacy Policy Updated: 2013-08-08

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