TweetFollow Us on Twitter

Using Vertical Retrace
Volume Number:1
Issue Number:9
Column Tag:C Workshop

Using the Vertical Retrace Manager"

By Robert B. Denny, President, Alisa Systems, Inc., MacTutor Editorial Board

This month, we look at some obscure but very useful features of the Macintosh operating system, and combine them in a complete example program, a CRT saver. The CRT saver does not require a desk accessory slot, nor must it be run as an application to get it installed. The example program also illustrates techniques for using low-level operating system features from C. As usual, the information presented here is meant to supplement that in Inside Macintosh.

The Vertical Retrace Manager

The Vertical Retrace Manager is used to schedule repetitive tasks at timed intervals. It gets its name from the fact that it is activated when the electron beam that paints the Mac screen "snaps back" to its starting place after painting the entire screen from top to bottom. This vertical retrace happens 60 times a second.

Making use of the Vertical Retrace Manager is easy. Simply fill in a data structure with a pointer to the task procedure you want to schedule and the time delay (in ticks). Then issue a Vinstall() with the pointer to that data structure. At each vertical retrace, the delay is decremented. When the number of ticks gets to zero, the task is called.

After the task completes, the Vertical Retrace Manager checks the number of ticks. If it is still zero, nothing further is done. If the task re-loads the tick count, the whole process is repeated. Thus, to have the task periodically scheduled, simply have it re-load the tick count with the desired interval.

The data structure is a queue element, a structure used for various purposes throughout the Mac operating system. The different flavors of queue elements have one thing in common. As suggested by the name, queue elements are used in applications where things are placed on a queue. Queues are typically used to serialize processing or to otherwise establish order. Generically, a queue element may be represented as:

struct QE
 { 
 struct QE *QLink; /* Link or NULL */
 short QType;  /* Type of element */
 char QData[1];  /* 1st byte of rest of data */
 };
#define QElem struct QE

The type of queue element is indicated by the value in the QType field. Types include IOQType, for input-output queues, DrvType, for the drive queue, EVType, for the event queue, FSQType for file system queues, and VType for the vertical retrace queue. The contents of the rest of the queue element is specific to the type. A structure definition for a vertical retrace queue element is shown below:

struct  VB
 {
 struct VB *qLink; /* Queue link pointer */
 short qType;  /* Always 1 (VType) */
 ProcPtr vblAddr;/* -> Task to be scheduled */
 short vblCount; /* Delay in ticks */
 short vblPhase; /* Phase (see below) */
 };
#define VBLTask struct VB

When you call Vinstall(), the operating system places your queue element at the end of the vertical retrace queue. This means that your task will get activated following those already scheduled. The VblPhase field is used to interleave tasks which are repetitively scheduled with the same delay so that they are executed in separate "slots".

You might be wondering why "VBL" is used when describing things associated with vertical retrace activity. The VBL stands for "vertical blanking" a synonym for vertical retrace. The two are interchangable.

There are a few things to be aware of when writing a VBL task. The task gets run asynchronously . Whenever the vertical retrace occurs, the current process is interrupted and control transfers to the Vertical Retrace Manager, which saves registers D0-D3 and A0-A3, then calls each task whose tick count has reached zero. When the last task completes (with an RTS), those registers are restored.

This has major consequences. First, the VBL task must save and restore any registers (other than D0-D3 and A0-A3) that it uses. Second, the VBL task must never make Memory Manager requests which allocate or free memory. Since many system services (e.g., resource manipulation) generate Memory Manager requests, this severely restricts activities inside a VBL task. Third, the execution time must be kept short because there may be many VBL tasks scheduled for a particular tick, and all must complete before the next retrace, 16.67 milliseconds later.

The most common way for an application to use a VBL task is to have it control flags and/or timers that are used by the application in its event loop. This way, the timing of application activity is controlled by the VBL task, while the time-consuming processing is done in the application itself.

Why no Memory Manager activity in a VBL task? Since the task is activated asynchronously, it may interrupt the application process right in the middle of Memory Manager services. At that time, the memory management data structures may be in an inconsistent state; a block may be "partially" deallocated, for example. Trying to do something else at that time would cause the whole thing to become corrupt.

VBL tasks have many uses. Any time you have animation to do, consider using a VBL task to make the motion smooth. If you rely on the consistency in timing of your application's event loop, you may be disappointed. When your system gets AppleTalk installed, for example, there can be a lot of asynchronous activity, which will upset your timing loops. Have a VBL task set a flag indicating that a certain amount of "real" time has elapsed, and use this knowledge to animate. Remember that you get sixty frames a second on the Mac screen, and the VBL task can schedule things sixty times a second, so there is no loss in scheduling bandwidth.

The Mac system contains several "standard" VBL tasks which handle the following:

• Check whether the stack and heap are getting too close to each other. This is the "stack sniffer" (every tick).

• Increment the global variable Ticks, the number of ticks since system startup (every tick).

• Handle cursor movement (every tick).

• Deglitch the mouse button and post mouse events (every other tick).

• Post a disk-inserted event if a disk was inserted (every 30 ticks).

In the CRT saver, the VBL task periodically examines the amount of time that has elapsed since the current application got a non-null event. If it has been long enough, the VBL task blanks the screen and sets a flag indicating this fact. That's it.

The GetNextEvent Filter

There is an undocumented "hook" in GetNextEvent() that allows special processing to be performed before control is returned to the calling application. In the global location JGNEFilter there is a pointer to a procedure that gets jumped-to just prior to returning to the application. In fact, the filter procedure completes with an RTS instruction which returns directly to the application.

When the filter procedure is entered, A1 points to the event record in the application's address space. The event has been dequeued and copied into the application's event record. Finally, the top of the stack contains the address of the instruction following the application's _GetNextEvent trap, and just under that is the boolean result being returned by GetNextEvent(). Be aware that this information was obtained by digging with MacsBug, and may change without notice in future operating system revisions.

It may be of interest that the "real" filter procedure appears to perform the following services (there may be more):

• Checks for and beeps the alarm clock.

• Handles the special "command shift" keys, which eject disks, etc.

The CRT saver intercepts the JGNEFilter and keeps track of how long it has been since the application received a non-null event from GetNextEvent(). Then it jumps to the "real" filter procedure.

INIT Resources

Each time the Mac is started up, the operating system installs ROM patches, loads keyboard maps and opens certain drivers. The mechanism used for this process is the INIT resource. You can make use of this feature of the Mac bootstrap code.

During startup, the boot code looks in the "System" file for up to 32 resources of type INIT, starting with ID=1. For each such resource found, the following steps are taken:

1. The INIT resource is loaded into the system heap.

2. DetachResource() is called, which "orphans" the resource, removing it from the map.

3. A JSR is made to the first location in the resource.

4. When the INIT code returns, via an RTS instruction, the first two locations in the INIT are bashed with NOP instructions.

This action may seem a little strange, so let's look at an INIT resource which installs a ROM patch.

First, the resource is loaded and detached, making it invisible to the Resource Manager. It is important to understand the need for detaching the resource. If you start an application on a new disk containing a System file, that disk becomes the new "system" disk. The current System file is closed, the System file on the new disk is opened, and all system resources start coming from the new System file.

When the old System file is closed, all resources that were loaded from there are released to make way for those in the new system. If the INIT resources were not detached after loading, they too would be released, with unfortunate results.

Once the INIT resource has been made permanently resident in the system heap, it is called at its first location, which is usually a jump to some one-time initialization code located at the end of the resource. This allows the initialization code to be chopped off with a _SetHandleSize after it is run, freeing up that system heap space.

The initialization code installs the ROM patch, computes the amount of space needed by the patch code only, then does a _SetHandleSize to reduce the resource's size in the system heap. Then it places a handle to itself in register D7 and returns to the boot code.

At this point, the boot code assumes that there is no need in the INIT resource for the jump to the initialization code, since it has run and may have been chopped off. So it uses that handle to bash the first 2 words of the INIT resource with No-Op instructions.

The CRT Saver

The example C program is a CRT saver which gets installed via an INIT resource, uses a VBL task to time the screen blanking, and uses the GetNextEvent filter to keep track of the last time the application received a non-null event. Please remember that this is an example, written to present and illustrate ideas. In real life, this small program would be written entirely in assembler, and would use the "normal" installation method just explained.

The example shows an alternate installation method, where the initialization code copies the action code to a locked-down area in the system heap and then releases the entire INIT resource. There are two bugs in the CRT saver, which I have purposely left for you to solve.

The first one should be easy. If the application does not call GetNextEvent, the time of last non-null event does not get updated, and the screen may be prematurely blanked. Hint: use the global variables MBTicks and KeyTime.

The other bug will be harder to fix (I have not solved it yet). The usual method for flashing a cursor on the screen (such as the TextEdit insertion bar) is to repeatedly XOR the pattern, which makes it flash white then black. If the cursor happens to be white (invisible) at the moment the screen is blanked, the effects of succeeding XOR's are reversed. The cursor's manager thinks the cursor is white, yet it was secretly bashed black by the screen clearing process.

Because the XOR method is "open loop", the manager never finds out that the cursor's state was reversed. So when it's time to move the cursor, the manager tries to XOR it as needed to make it invisibly white, but instead leaves the space black. This has the effect of leaving behind a ghost of the cursor. Keep in mind that TextEdit isn't the only agent that uses flashing cursors.

The example uses specifics of the Apple 68000 Development System, and the Consulair Mac C compiler. You may need to take different approaches to producing the INIT resource and accessing static variables from both C and assembler. In addition, the interface into C from the Vertical Retrace Manager and the GetNextEvent filter may differ.

/*
  *Screen Saver INIT Resource
  *
  *Written by:   Robert B. Denny, Alisa Systems, Inc.
  *June, 1985
  *Written for:  Apple Computer MDS Development System and Consulair 
Mac C™
  *This program uses specific features of the MDS system and Mac C
  *and will almost certainly require modifications for other systems.
  *
  *  LINKER COMMAND FILE:
  *--
  */OUTPUT Dev:CRTSave.INIT
  */Globals -0
  */Type 'RSRC'
  */Resources
  *CRTSav
  *
  *$
  *--
  *
  *Copyright (C) 1985, MacTutor Magazine
  *
  *Permission granted to use only for non-commercial purposes.  This 
notice must be
  *included in any copies made hereof.  All rights otherwise reserved.
  *
  *Warning: This code was edited for publication which could have introduced 
minor errors
  */
#Options R=4/* Mac C: Use R4 to access globals */

#include"MacDefs.H"/* Basic Macintosh structures */
#include"Events.H" /* Event Manager & Event Record */
#include"OSMisc.H" /* Queue Elements and VBL defs */

#define TRUE1
#define FALSE  0
#define NULL0
#define SAVE_DELAY  18000 /* 5 Minutes in ticks.  Saver delay */

/*
  * Definitions which allow easy to read access to system variables.
  */
#define Ticks    (*((unsigned long *)(0x16A)))     /* Ticks since boot 
time */
#define GrayRgn  (*((unsigned long *)(0x9EE)))     /* Desktop region 
w/rounded corners */
#define JGNEFilter (*((ProcPtr *)(0x29A)))   /* -> GetNextEvent filter 
procedure */

/*
  * Screen geometry parameters work on both 128K and 512K
  */
#define ScreenLow((unsigned long *)(0x7A700))      /* -> base of screen 
map */
#define scrnLongwords  (5472) /* No. of longwords in screen map */

/*
  * Static variables for the VBL Task and the GNEFilter
  */
VBLTask VBQElement;  /* Vertical Retrace Queue Element */
unsigned long EvTicks;  /* 'Ticks' value of  last non-null event */
ProcPtr SavedJGNEFilter;  /* Entry point of "normal" GNE filter proc 
*/
unsigned short BlankScreenFlag;  /* TRUE means screen already blanked 
*/


/*
  * The following assembler code executes as called from the Mac boot 
process as an INIT
  * resource.  Here is an example where C is just not appropriate.
  */
#asm
 RESOURCE 'INIT' 28 'CRT Saver' 80 ; System/Locked att's
  
 Include MacTraps.D
 Include SysEquX.D
 
 XDEF InitSaver
InitSaver:
 MOVE.L #(TheEnd-TheStart),D0 ; Allocate space for saver
 _NewPtr ,SYS  ; Locked, in system heap
 BNE @10  ; (not enough space)
   MOVE.L A0,A1         ; A1 -> destination area
   LEA  TheStart,A0       ; A0 -> source area
   MOVE.L #(TheEnd-TheStart),D0    ;Size of code & static data
   _BlockMove  ; Copy stuff to allocated block
 MOVE.L A1,A0  ; A0 -> Moved code & data
 LEA  (OurStatics-TheStart)(A0),A0 ; A0 -> "Top" of real statics
 MOVE.L Ticks,EvTicks(A0) ; Initialize Last Event Ticks
 MOVE.L JGNEFilter,SavedJGNEFilter(A0) ; Save "real" GNE filter proc
 PEA  (GNEIntfc-TheStart)(A1) ; Push -> to GNE filter interface
 MOVE.L (SP)+,JGNEFilter  ; Now we catch GNE calls also
 LEA  VBQElement(A0),A0 ; A0 -> VBL Queue Element
 PEA  (VBLIntfc-TheStart)(A1) ; Push -> VBL Service Task
 MOVE.L (SP)+,vblAddr(A0) ; Fill in entry point in Q-Elem
 MOVE.W #Vtype,qType(A0)  ; Indicate the queue element type
 MOVE.W #300,vblCount(A0) ; Schedule at 5 sec. intervals
 Move.W #5,vblPhase(A0) ; Off-the-wall phasing
 _VInstall; Start the VBL task
;
; We finish up by disposing of ourselves.
;
@10:
 LEA  InitSaver,A0 ; A0 -> Ourselves (INIT resource)
 MOVE.L A0,(A0)  ; Make a handle to ourselves
 MOVE.L A0,D7  ; Save handle in D7 for MacBoot
 _RecoverHandle ,SYS ; Get our real resource handle
 _DisposHandle ; Free ourselves
 RTS
#endasm

/*
  * The rest of this is copied into the allocated non-relocatable block 
and runs from there.
  * There are 2 interface routines in assembler which call C to do the 
real work, one for
  * the VBL task and the other for the GNE filter.  Also, there is space 
allocated for our
  * local static variables.
  */
#asm

TheStart: ; Static data goes here via A4
 DCB.B  32,0; Enough room for statics
OurStatics: ; "Top" of static area


;
; Interface to C for Vertical Blanking Task
;
VBLIntfc: ; Interface for VBL task service
 MOVEM.LA4-A5/D4-D7,-(SP) ; Save registers
 LEA  OurStatics,A4; A4 -> Our static variable area
 JSR  VBLRoutine ; Call C for dirty work
 MOVEM.L(SP)+,A4-A5/D4-D7 ; Restore registers
 RTS  
;
; Interface to C for GetNextEvent filter.  This must finish up
; by jumping to the "real" filter whose address was originally 
; in the global "JGNEFilter".
;
GNEIntfc:
 MOVEM.LA1-A5/D0-D7,-(SP) ; Be safe.
 LEA  OurStatics,A4; A4 -> Our static variable area
 MOVE.L A1,D0  ; Pass -> Event Record as parameter to C
 JSR  GNEFilter  ; Call C to filter the events, etc.
 MOVE.L SavedJGNEFilter(A4),A0; Where to next?
 MOVEM.L(SP)+,A1-A5/D0-D7 ; Restore saved reg's
 JMP  (A0); Jump to "real" GNE filter
#endasm

/*
  * Vertical Blanking task.  This is periodically rescheduled and handles 
watching for 
  * no-activity intervals and blanking the screen if more than a specified 
time elapses
  * between non-null events.
  */
VBLRoutine()
 {
 unsigned long *lp;
 unsigned long n;
 extern GNEIntfc();  /* Declare this as a proc */
 
 VBQElement.vblCount = 300; /* Reschedule ourselves */
 
 /*
   * If the screen is already blank, do nothing.
   * You might enhance this by doing something interesting with the cursor 
inside 
   * this "if" statement, knowing you'll get here every 5 seconds.
   */
 if(BlankScreenFlag)
 {
 return;
 }
 /*
   * Blank the screen if there hasn't been a non-null event in the last 
SAVE_DELAY ticks.
   */
 if((Ticks - EvTicks) > SAVE_DELAY) 
 {
 BlankScreenFlag = TRUE;  /* Set the blanked flag */
 HideCursor ();  /* Hide the cursor from blanking */
 lp = ScreenLow;
 for(n=0; n<scrnLongwords; n++)  /* Blank the screen */
 *lp++ = 0xFFFFFFFF;
 ShowCursor ();  /* Restore the cursor */
 }
 return;
 }

/*
  * GNE Filter Procedure
  *
  * If there has been either a key press or mouse click since the screen 
was blank, restore the
  *  screen and switch the GNEFilter back to normal.
   */
ProcPtr GNEFilter(ep)
EventRecord *ep; /* -> Event Record just dequeued */
 {
 if(ep->what != nullEvent)/* If appl is getting non-null event */
 {
 EvTicks = Ticks;/* Remember ticks at non-null event */
 if(BlankScreenFlag) /* If the screen is black */
 {
 BlankScreenFlag = FALSE; /* It's going to get refreshed */
 DrawMenuBar (); /* Draw the menu bar, then */
 PaintBehind (FrontWindow (), GrayRgn);/* Draw all windows and desktop 
*/
 }
 }
 return;
 }

#asm

TheEnd: ; Mark the end of the resident code/data
;
; ----- END OF CODE & DATA WHICH IS COPIED TO ALLOCATED BLOCK -----
;
#endasm
 

Community Search:
MacTech Search:

Software Updates via MacUpdate

VOX 2.8.24 - Music player that supports...
VOX just sounds better! The beauty is in its simplicity, yet behind the minimal exterior lies a powerful music player with a ton of features and support for all audio formats you should ever need.... Read more
Dropbox 24.4.17 - Cloud backup and synch...
Dropbox is an application that creates a special Finder folder that automatically syncs online and between your computers. It allows you to both backup files and keep them up-to-date between systems... Read more
OmniPlan Pro 3.7.1 - Professional-grade...
With OmniPlan Pro, you can create logical, manageable project plans with Gantt charts, schedules, summaries, milestones, and critical paths. Break down the tasks needed to make your project a success... Read more
OmniPlan 3.7.1 - Robust project manageme...
With OmniPlan, you can create logical, manageable project plans with Gantt charts, schedules, summaries, milestones, and critical paths. Break down the tasks needed to make your project a success,... Read more
Adium 1.5.10.4 - Popular instant messagi...
Adium is a fast and free instant messaging client which supports AIM, ICQ, Jabber, MSN, Yahoo!, Google Talk, Yahoo! Japan, Bonjour, Gadu-Gadu, Novell Groupwise, SIP/SIMPLE (Text), and Lotus Sametime... Read more
SteerMouse 5.1 - Powerful third-party mo...
SteerMouse is an advanced driver for USB and Bluetooth mice. It also supports Apple Mighty Mouse very well. SteerMouse can assign various functions to buttons that Apple's software does not allow,... Read more
File Juicer 4.57 - $18.00
File Juicer is a drag-and-drop can opener and data archaeologist. Its specialty is to find and extract images, video, audio, or text from files which are hard to open in other ways. In computer... Read more
1Password 6.7 - Powerful password manage...
1Password is a password manager that uniquely brings you both security and convenience. It is the only program that provides anti-phishing protection and goes beyond password management by adding Web... Read more
CleanMyMac 3.8.1 - $39.95
CleanMyMac makes space for the things you love. Sporting a range of ingenious new features, CleanMyMac lets you safely and intelligently scan and clean your entire system, delete large, unused files... Read more
Monolingual 1.7.8 - Remove unwanted OS X...
Monolingual is a program for removing unnecesary language resources from OS X, in order to reclaim several hundred megabytes of disk space. If you use your computer in only one (human) language, you... Read more

Latest Forum Discussions

See All

Olli by Tinrocket (Photography)
Olli by Tinrocket 1.0 Device: iOS iPhone Category: Photography Price: $2.99, Version: 1.0 (iTunes) Description: Get drawn in with Olli by TinrocketOlli instantly turns your everyday moments into hand-drawn art and animations. • Watch... | Read more »
Penarium (Games)
Penarium 1.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0 (iTunes) Description: | Read more »
Fire Emblem Heroes is way more profitabl...
Profits for Nintendo's mobile game Fire Emblem Heroes are apparently impressive enough to beat out other Nintendo titles likeSuper Mario Run, despite having 10 times fewer downloads. [Read more] | Read more »
Classic series Robot Unicorn Attack 3 no...
The classic Adult Swim browser game, Robot Unicorn Attack, branched off into a series of popular mobile games. Now, the latest entry into the series, Robot Unicorn Attack 3, is available for iOS and Android mobile devices. [Read more] | Read more »
Sudoku Sweeper (Games)
Sudoku Sweeper 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: A minimalist mashup of Minesweeper and Sudoku. Logic puzzle perfection. Every row, column and zone contains a bomb and one of... | Read more »
Under Leaves (Games)
Under Leaves 1.0.0 Device: iOS Universal Category: Games Price: $1.99, Version: 1.0.0 (iTunes) Description: Journey into the forest, the jungle or the depths of the deep blue sea. Find chestnuts for the pigs, a caterpillar for the... | Read more »
Ninja Pizza Girl (Games)
Ninja Pizza Girl 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: In the not-so-distant future, rampart traffic congestion has resulted in only one way to deliver pizzas across town in thirty... | Read more »
SCRAP (Games)
SCRAP 1.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.0 (iTunes) Description: That day, for no apparent reason, SCRAP decided to wake up and run. He had to, because his activation was a mistake the "Factory" could... | Read more »
The Bunker (Games)
The Bunker 1.1 Device: iOS Universal Category: Games Price: $3.99, Version: 1.1 (iTunes) Description: The critically acclaimed console hit "The Bunker" comes to iOS, The groundbreaking live-action thriller adventure set in a real... | Read more »
Die With Glory (Games)
Die With Glory 1.2.0 Device: iOS Universal Category: Games Price: $2.99, Version: 1.2.0 (iTunes) Description: Die with Glory is an epic adventure game where your goal is to die in glorious fashion. You must help Sigurd, a brave old... | Read more »

Price Scanner via MacPrices.net

New System Clock for macOS by B-Eng Now Avail...
Fehraltorf, Switzerland based B-Eng has announced the release and immediate availability of System Clock, the company’s new system monitor and information app developed exclusively for macOS. System... Read more
DEVONtechnologies Celebrates 15th Anniversary...
DEVONtechnologies celebrates its 15th company anniversary with a 30% discount on all its software products from May 1st through 5th, 2017. In spring 2002, DEVONtechnologies opened its website and... Read more
WaterField Designs Invites Customers to Help...
San Francisco based WaterField Designs invites customers and air travelers to participate in developing the next generation in-flight travel case, the Air Porter. Frustrated with limited legroom,... Read more
Save up to $260 with Apple refurbished 12-inc...
Apple has Certified Refurbished 2016 12″ Retina MacBooks available for $200-$260 off MSRP. Apple will include a standard one-year warranty with each MacBook, and shipping is free. The following... Read more
Digital Paper Tablet Offers Distraction Free...
I typically spend 8-10 hours a day gazing at the screens in my laptops and iPad, as tools of my livelihood, I don’t as a rule use electronic devices for pleasure reading. I subscribe to a daily... Read more
“Today at Apple” Bringing New Educational Ses...
Apple has announced plans to launch dozens of new educational sessions next month in all 495 Apple Stores ranging in topics from photo and video to music, coding, art and design, and more. The hands-... Read more
Smart Finance Free Comprehensive Personal Fin...
Moscow-based indie developer, Alexander Survillo has announced the release and immediate availability of Smart Finance: Personal Finance, Budget & Money 1.1.4, an update to his comprehensive... Read more
12-inch 1.1GHz Retina MacBooks on sale for $1...
B&H has 12″ 1.1GHz Retina MacBooks on sale for $100 off MSRP. Shipping is free, and B&H charges NY & NJ sales tax only: - 12″ 1.1GHz Space Gray Retina MacBook: $1199.99 $100 off MSRP - 12... Read more
13-inch 2.7GHz Retina MacBook Pro on sale for...
B&H Photo has the 13″ 2.7GHz Retina MacBook Pro on sale for $130 off MSRP. Shipping is free, and B&H charges NY & NJ tax only: - 13″ 2.7GHz/128GB Retina MacBook Pro (MF839LL/A): $1169 $... Read more
15-inch 2.2GHz Retina MacBook Pros available...
B&H Photo has the 15″ 2.2GHz Retina MacBook Pro available for $200 off MSRP including free shipping plus NY & NJ sales tax only: - 15″ 2.2GHz Retina MacBook Pro (MJLQ2LL/A): $1799.99 $200 off... Read more

Jobs Board

*Apple* Retail - Multiple Positions- Chicago...
Job Description: Sales Specialist - Retail Customer Service and Sales Transform Apple Store visitors into loyal Apple customers. When customers enter the store, Read more
*Apple* Systems Engineer - California Polyte...
Cal Poly, San Luis Obispo Apple Systems Engineer Department: ITS - Customer & Tech Support (134900) College/Division: Academic Affairs Salary Range: Position Read more
*Apple* Mobile Master - Best Buy (United Sta...
**501042BR** **Job Title:** Apple Mobile Master **Location Number:** 000416-East Lansing-Store **Job Description:** **What does a Best Buy Apple Mobile Master Read more
Best Buy *Apple* Computing Master - Best Bu...
**501195BR** **Job Title:** Best Buy Apple Computing Master **Location Number:** 000211-Colorado Blvd-Store **Job Description:** **What does a Best Buy Apple Read more
*Apple* Mac Computer Technician - GeekHampto...
…complex computer issues over the phone and in person? GeekHampton, Long Island's Apple Premium Service Provider, is looking for you! Come work with our crew Read more
All contents are Copyright 1984-2011 by Xplain Corporation. All rights reserved. Theme designed by Icreon.