Power Macintosh: Type 11 & No FPU Errors Technote (7/96)

Article Created: 10 November 1995
Article Reviewed/Updated: 02 July 1996

TOPIC 
---------------------------------------------------------
This Technote explains some of the causes of "Type 11" 
and "No FPU Installed" errors, along with debugging 
hints to help you find and fix them. It also focuses 
on what you as a programmer can do to prevent such 
errors.

DISCUSSION 
----------------------------------------------------
Both Type 11 and No FPU Installed errors occur on 
Power Macintosh computers, depending on various 
factors. Both error messages are the result of 
programming errors. The No FPU Installed error usually 
means that your program is executing data rather than 
instructions. The Type 11 error is any error (such as 
a bus error) in native code.
NOTE: In this Technote, I will occasionally mention 
third-party products by name. If a third-party product 
is mentioned by name, it's meant to be a possible 
solution for you to investigate, not a recommendation. 
DTS doesn't evaluate third-party tools, nor maintain 
complete lists of possible third-party solutions. You 
should consult catalogs of development tools such as:
* Macintosh Development Tools & Languages
* the Redgate Macintosh Registry
* the ubiquitous Internet
* the APDA catalog and
* reviews in technical magazines to find a product 
that fits your needs.
There are many Web sites on the Internet ‹‹ for 
example, Apple's Third-Party Development Products 
Database at  lists many Macintosh development tools. 
Perhaps you may find an appropriate tool to meet your 
development needs in this way.

About "No FPU Installed" Errors
===============================
On a Power Macintosh computer, the error message No 
FPU Installed usually means your code has jumped to a 
non-code area and is executing garbage. Somewhere in 
that data (which is being interpreted as instructions) 
is an instruction whose op code begins with the hex 
value F. No FPU Installed is equivalent to a Type 10 
Error ‹‹ i.e., your program has attempted to execute 
an unknown instruction op code starting with the hex 
value F.
On a Power Macintosh, No FPU Installed means that some 
program has jumped to an area of data and has tried to 
execute any data word starting with the hex value F. 
The PowerPC chip has floating point support built in, 
but that floating-point support is different from the 
Motorola 680x0 family floating- point support. The 
Motorola 680x0 family uses an external floating-point 
unit. (There are also external memory management units 
(MMUs) and other specialized coprocessors.) Motorola 
680x0 CPUs use instructions starting with hex value F 
as instructions for these coprocessors.

680x0 Microprocessor Instructions
---------------------------------
All Motorola 680x0 microprocessors have instructions 
consisting of at least one word (the operation word); 
some instructions can have up to eleven words (see the 
Motorola MC68020 32-bit Microprocessor User's Manual, 
Third edition, page 3-1.) The operation word 
determines what kind of instruction is to be executed. 
For example, the instruction
MOVE.B D1, D2
translates to the hexadecimal value
1401
This instruction starts with the hex value 1. The 
instruction
FMOVE.X FP3,-(A7)
translates to
F227 6980
This instruction starts with the hex value F.

F-line Instructions
-------------------
The Motorola 680x0 architecture was originally 
designed to support a floating- point coprocessor 
chip. This chip, the Floating Point Unit (FPU), 
communicates with the CPU via a special set of 
instructions called F-line instructions. These 
instructions always start with an operation word 
beginning with the hex value F.
A program can be compiled to take advantage of the 
hardware assistance the FPU provides, and thus yield 
faster floating-point calculations than would be 
available with SANE (the Standard Apple Numerics 
Package). Such programs would have instructions in the 
program which start with the hex value F. A program 
only using SANE would never have an instruction 
starting with the hex value F.
NOTE: Some Macintosh models, such as the Macintosh SE/
30, the Macintosh IIci, and the Macintosh IIfx, 
shipped with an FPU coprocessor installed. Other 
680x0-based Macintosh computers, such as the Macintosh 
IIsi and the Macintosh Color Classic, had an optional 
FPU coprocessor. For these machines, it was possible 
to purchase an optional card with an FPU coprocessor.

68040 & 68040LC Microprocessors
-------------------------------
With the introduction of the 68040 and 68040LC chips, 
things got a bit more complicated. The 68040 
microprocessor has most of the 68882 FPU included on 
the chip. Not everything in the 68881/68882 FPU is in 
the 68040 chip, however ‹‹ just the routines that 
Motorola determined were most frequently used. The 
rest of the FPU routines are automatically emulated by 
software. Because the FPU is "built-in," as it were, 
the 68040 chip handles instructions that start with an 
operation word beginning with the hex value F by 
itself. There is no way to add a coprocessor to a 
68040 chip; the instructions are never brought out of 
the chip itself.
The 68040LC is a cost-reduced version of the 68040 
chip. Savings came about by removing the FPU portion 
of the chip. Not only does a 68040LC chip have no FPU, 
there is no way to add one.

The Power Macintosh
-------------------
Power Macintosh computers emulate a Motorola 68040LC, 
i.e., a machine without FPU support. When you get a 
bomb with the message No FPU installed, it means some 
instruction has been executed with an operation word 
starting with the hex value F, and that your program 
is running on a machine without a FPU. This machine 
could be one of the following:
* a Macintosh with a 68020 or 68030 microprocessor and 
no FPU coprocessor
* a Macintosh with a 68040LC microprocessor (which can 
never have a FPU)
* a Macintosh with a PowerPC chip running 68K code in 
emulation (since the 68K emulator emulates a 68040LC 
microprocessor).
Power Macintosh computers contain very fast floating-
point support as part of the CPU. This floating-point 
support is different from the floating-point support 
provided by the Motorola 680x0 microprocessors. Inside 
Macintosh:PowerPC Numerics, describes Power Macintosh 
floating-point support.

Defining a Type 11 Error
========================
A Type 11 error means an illegal interrupt vector on a 
680x0 machine. On a Power Macintosh, a Type 11 error 
is any exception in native code not handled by one of 
the installed exception handlers. On a Power 
Macintosh, a Type 11 error can be almost any error 
that occurred in native code. Type 11 errors may 
include:
* an address error
* a bus error
* an illegal instruction error that occurred in native 
code.
The exception handlers installed for native code don't 
correctly handle the particular condition which was 
raised, and the error is returned back to the System 
Error manager via the Mixed Mode manager. The System 
Error manager maps all such exceptions to the system 
error Type 11 Error.
If you install Macsbug 6.5.2 or later, some Type 11 
errors may be reported as a PowerPC unmapped memory 
exception. This is equivalent to a bus error, i.e., an 
error indicating your program is accessing memory that 
doesn't exist.
The Modern Memory Manager was designed to be less 
forgiving than the classic (68K) Memory Manager. 
Disposing of something twice, disposing of memory that 
was never allocated, and other memory handling 
problems will often generate a Type 11 error, while on 
a 68K machine the problem may go unnoticed.

Programming Mistakes Causing Type 11 Errors
===========================================
The following sections give you examples of 
programming mistakes that may cause Type 11 errors.

Example #1: Writing Past the End of an Array
--------------------------------------------
Writing past the end of an array can be a subtle and 
difficult-to-find bug. Example #1 shows you why.
;=======================================================
;Begin C Code
;
void IAmGoingToCrash(void)

Str27   badArray;
BlockMoveData("\pThis string is too long for this array", 
badArray, 39);

;
;End C Code
;=======================================================

NOTE: I've made the bug very obvious; it may not be 
quite so obvious, however, in your code. In this 
example, I've put a string of 39 characters into an 
array defined to hold 27 characters. This overwrites 
the stack, which contains such useful things as your 
return address. On a 68K Mac, this causes a bus error. 
On a PowerPC Mac in 68K emulation, this causes a bus 
error. On a Power Macintosh in native code, this 
causes a Type 11 error.

Example #2: Using a Poorly Initialized Pointer or Handle
--------------------------------------------------------
If your program tries to use an uninitialized or badly 
initialized pointer, it can generate a Type 11 error. 
Here is what happens in Example #2:
;=======================================================
;Begin C Code
;
Ptr badPointer = (Ptr)-2;
*badPointer = 0;
;
;End C Code
;=======================================================

NOTE: I've made the bug very obvious; it may not be quite so 
obvious, however, in your code. In this example, I've created a 
pointer to non-existent memory (-2 isn't a valid address) and then 
tried to access the memory to which the pointer refers. On a 68K Mac, 
this causes a bus error. On a PowerPC Mac in 68K emulation, this 
also causes a bus error. On a Power Macintosh in native code, this 
causes a Type 11 error.

Other Situations Causing Type 11 Errors
=======================================
The following sections document some of the known bugs in 
various products that may cause Type 11 errors.

Color Picker vs Third-Party SCSI Drivers
----------------------------------------
One reproducible problem stems from a known bug in several third-
party SCSI hard disk drivers. The bug causes the Color Picker to crash 
when trying to resolve a boot volume alias it makes at startup time. 
This problem exists in any system when Color Picker 2.0 or 2.0.1 is 
installed and the boot volume is not a removable drive. The 
fundamental cause of the problem is that the SCSI driver incorrectly 
marks the boot drive as a removable drive during the boot process 
and changes it to be properly marked as a fixed device after startup. 
To find its code, the Color Picker resolves the boot volume alias it 
made during startup. Since the alias passed to the Alias Manager is 
for a removable drive, the Alias Manager can't resolve the alias 
(since the device is now marked as fixed.) The Color Picker design 
did not anticipate the boot volume not being found. This results in a 
Type 11 error. The fix is to upgrade your SCSI driver to a later 
version.

Calling a Routine That May Move Memory at Interrupt Time
--------------------------------------------------------
The Apple Media Kit, release 1.2, had a problem that could cause 
random errors. During a VBL task, AMK was calling SetCCursor. 
SetCCursor can possibly move memory. Moving memory during 
interrupt time is a very bad idea. The Memory Manager may be in an 
unstable state, such as compacting memory, when an interrupt 
routine gets called. This can cause a Type 11 error in native code.
A replacement cursor.c file has been provided in the Apple Media 
Tool/Programming Environment Runtime folder, and we do have a 
replacement Runtime Maker:Codes:Program file for Apple Media 
Tool. If you are currently developing titles, replacing these files and 
rebuilding your projects will remove the bug.

Not Enough Heap Space
---------------------
There are some situations where having small amounts of memory 
available in the system heap may lead to a Type 11 error. As an 
example, if the shared library manager can't load a shared library, 
you may get a Type 11 error. This can happen when QuickTime tries 
to load a decompressor for certain kinds of images.

Writing Past the End of an Array
--------------------------------
In OpenTransport 1.0.5 or earlier, there was a bug in the TCP/IP 
control panel code that could corrupt memory if there were more 
than 256 zones and a MacIP server was found in a zone past the 
256th zone. Under these conditions, the control panel code wrote 
past the end of one of its buffers. This bug would manifest itself if the 
user opened the select zone dialog and the TCP/IP control panel was 
left open long enough for the NBP lookup calls for zones past the 
256th zone to complete. This is corrected in OpenTransport 1.0.6 and 
later, but is given here as an example of a Type 11 error.

Insufficient Stack Space
------------------------
Heavy use of local variables or recursion may cause your program to 
run out of stack space. When this happens, you may have crashes 
that are difficult to track down. Increasing your program's stack is 
one solution. Whenever you are using a large number of local 
variables or recursive routines, you should increase your program's 
stack (using the procedure listed in Inside Macintosh: Memory on 
page 1-40).
As an extreme example, a faceless background application 
(documented in Technical Note PS 2) has only a 2K stack by default. 
A 68K application has 24K of stack on most modern machines (8K if 
no Color QuickDraw is installed, 32K if A/UX is installed.) You can 
use the low memory accessor function LMGetDfltStack to find your 
current stack size. Native QuickDraw has several changes in 
algorithms that have increased the size of some structures. PowerPC 
alignment issues may cause the size of data structures to increase. 
Check your compiler documentation for further details.
To help detect collisions between the stack and the heap, a Òstack 
snifferÓ VBL task is installed that compares the current ends of the 
stack and heap and generates a system error 28 in case of a collision. 
Unfortunately, the Thread Manager is forced to disable the stack 
sniffer whenever it is installed. (This is because threads can have a 
stack in places where the stack sniffer doesn't expect them; if the 
stack sniffer is enabled, it would generate a system error 28.) This 
means you don't have the same level of protection as you did under 
older system software versions without the Thread Manager 
installed.

Too Much Recursion in QuickDraw
-------------------------------
Native QuickDraw before version 2.4.1 used a recursive routine to 
handle regions. This recursive code could cause your stack to run 
into the heap when handling certain region shapes. Version 2.4.1 of 
QuickDraw changed to a non-recursive routine which eliminates 
this error. (You can detect the version of QuickDraw using the 
Gestalt selector Ôqd Ôwhich returns a version.) In general, recursion 
on PowerMacs is dangerous unless you have substantial stack space 
available; PowerPC stack frames are very large, and putting many of 
them on the stack may quickly exhaust available stack.

Interrupts Not Handled by Device Drivers
----------------------------------------
Some Type 11 errors may legitimately be illegal interrupt vector 
errors, rather than simply unhandled exceptions in native code. If a 
device driver for a NuBus or PCI card does not install an interrupt 
service routine, but the card raises an interrupt, you will receive a 
Type 11 error. This will happen whether you are running in 68K 
code or PowerPC code. The only solution for such a problem is to 
update the driver to correctly handle the interrupt issued by the card.

Other Programming Errors
========================
Common programming errors may cause Type 11 or No FPU 
Installed errors. These include the same kinds of errors that usually 
result in address errors on 680x0-based Macintosh computers. For 
example:
* Indexing through an array incorrectly so that your program goes 
outside the memory allocated for that array (as demonstrated above).
* Disposing of memory twice
* Disposing of memory that was never allocated
* Calling DisposeHandle on a resource handle (use DisposeResource 
instead, to ensure that the Resource Manager doesn't lose handles 
behind its back.)

Some Techniques To Help Avoid Type 11 Errors
============================================
The following techniques may help resolve situations that might 
lead to Type 11 errors:
* Test your code carefully.
* Install the Debugging Modern Memory Manager, available on the 
Tool chest Developer CD. This version of the Modern Memory 
Manager has additional checks installed which allow you to track 
down and eliminate many memory management bugs.
* Use extensions such as EvenBetterBusError (found on the Tool 
chest Developer CD) in conjunction with Macsbug 6.5.2 or later, to 
detect use of uninitialized pointers or handles.
* Use third-party testing tools such as QCª by Onyx or MemoryMineª 
by Adianta.
IMPORTANT: It goes without saying that good testing before you 
release a product will prevent expensive customer support calls later 
on.

User-Level Recommendations
--------------------------
Here are some user-level suggestions recommended by Apple for 
unexplained Type 11 or No FPU installed errors:
1. Upgrade your hard disk driver(s) to the latest version available. 
There are some known problems between SCSI Manager 4.3 and 
some SCSI disk drivers. Starting with System 7.5, the SCSI Manager 
4.3 is installed on all Macintosh Quadras and Power Macintosh 
computers. There are some known programming problems in some 
older third-party disk drivers.
2. Upgrade to the latest System Software appropriate for your system. 
Several significant bug fixes in system updates should reduce the 
number of Type 11 and No FPU Installed errors you encounter.
3. Do a clean install of your System Software. Use the Extensions 
Manager control panel to determine if any additional control panels 
or extensions are conflicting with your system software.
4. Some Type 11 errors may result from corrupted PRAM. 
Unfortunately, most of extended PRAM is undocumented. (See 
Inside Macintosh:Operating System Utilites, chapter 7, Parameter 
RAM Utilities, for what details are documented.) You can restore 
your default PRAM values by holding down Command-Option-P-R 
at system startup time, or by using a shareware utility such as 
TechTool.
5. Make sure you are not using composite RAM in a Power 
Macintosh. Memory specifications are in the developer hardware 
notes for each computer.
6. Some users claim that installing the shareware extension 
SoftwareFPU cuts down on No FPU Installed problems. This 
extension emulates the Motorola FPU (at a considerably slower 
speed), thus preventing bombs from software which incorrectly 
makes FPU calls. This may alleviate no FPU Installed errors, but it 
doesn't address the fundamental problem, namely that some 
software is executing unexpected data or making illegal calls to a 
non-existent FPU.
7. Upgrade any software you find that causes repeatable errors.

Summary
=======
There are no easy solutions for handling Type 11 Error or No FPU 
Installed errors. Only careful debugging and testing can reduce the 
number and frequency of these errors. Most problems stem from 
common programming errors.

Further Reference
-----------------
* Inside Macintosh, PowerPC System Software, Addison-Wesley
* Inside Macintosh:PowerPC Numerics, Addison-Wesley
* Macsbug Reference and Debugging Guide, Addison-Wesley
* Macsbug Release Notes, part of the distribution of Macsbug
* Motorola MC68020 32-bit Microprocessor User's Manual, Third 
edition (available from Motorola)
* PowerPC Microprocessor Family: The Programming Environment 
(available from IBM or Motorola)
* Inside Macintosh:Memory, Addison-Wesley

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Article Change History:
02 Jul 1996 - Added Fax Doc word
09 Apr 1996 - Removed keyword.
08 Feb 1996 - Added keyword.
Copyright 1995-96, Apple Computer, Inc.

Keywords: kppc,supt,ksts,hts,ktoptil,kfax
==================================================================
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ArticleID: TECHINFO-0018912
19960724 15:55:27.00