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Apple II
Technical Notes
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Developer Technical Support
AppleTalk
#2: ProDOS 8 Compatibility on the IIe and IIGS
Written by: Mark Day November 1988
This Technical Note describes areas which could cause an application to run
under the AppleShare Apple IIe workstation software, but fail under the Apple
IIGS workstation software.
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o If code is running in auxiliary memory in emulation mode (e.g.,
ProDOS 8 programs that run code from auxiliary memory), make sure
$0100 in auxiliary memory is set to the normal stack pointer and
$0101 in auxiliary memory is set to the auxiliary (alternate)
stack pointer. (See page 93 of the Apple IIe Technical Reference
Manual.)
o Make sure ProDOS calls are not made from auxiliary memory; Apple
has never recommended doing this, and it is not supported.
o Make sure interrupts are enabled when making ProDOS 8 calls.
o Make sure interrupts are not disabled for long periods of time,
nor for a high percentage of time. Whenever interrupts are
disabled, there is a chance that an AppleTalk packet will be
missed (which could cause AppleShare volumes to be unmounted).
The more interrupts are disabled, the more likely that packets
will be missed. This risk is inherent for any application that
disables interrupts (directly or indirectly), therefore,
interrupts should be disabled with discretion and only when
absolutely necessary.
o Make sure programs get the completion routine return address from
the GetInfo call when they are started.
o Make sure to identify AppleTalk by calling GetInfo and checking
for an invalid call number error (which means AppleTalk is not
present). Do not use the ATLK signature bytes for identification.
See Apple II AppleTalk Technical Note #1, Identifying AppleTalk.
Further Reference
o Apple IIe Technical Reference Manual
o Apple II AppleTalk Technical Note #1, Identifying AppleTalk