Programming Release Notes
5.10 Privileged Data Structures Updates
For performance reasons, the IPL is not verified if SYSTEM_CHECK is set to
zero (the default). Incorrect code may cause the system to hang if a reschedule to
another CPU occurs during execution of these routines from process context (for
example, below IPL$_RESCHED).
5.11 Applications Using Floating-Point Data
V8.2
The Itanium® architecture implements floating-point arithmetic in hardware
using the IEEE floating-point formats, including IEEE single and IEEE double.
The Alpha hardware supports both IEEE and VAX floating-point formats. On
OpenVMS Alpha, the compilers generate code to use the VAX formats by default
with options to use the IEEE formats.
On OpenVMS Integrity servers, the compilers generate code to use the IEEE
formats by default with options to use the VAX formats. HP recommends the use
of IEEE formats on Integrity servers unless applications need to process VAX
floating-point binary data that has been generated on VAX or Alpha systems.
For details about using VAX formats on OpenVMS Integrity servers, refer to the
OpenVMS Floating-Point White Paper on the following website:
http://www.hp.com/products1/evolution/alpha_retaintrust/openvms/resources.html
5.11.1 IEEE Floating-Point Filter (Integrity servers Only)
V8.3
In order to allow floating point exceptions to conform completely with IEEE-
Std 754-1985, Intel provides a function called an IEEE filter. An application
developer who wants to use this function can place a call to this function code
within a normal OpenVMS exception handler. When an exception occurs, the
filter can decode the floating point instructions that caused the exception, as
well as decoding the IEEE rounding modes and precision, and determining the
operands that caused the exception
To obtain a copy of this filter, access the following Intel Web site and look for the
OpenVMS header:
http://www.intel.com/cd/software/products/asmo-na/eng/219748.htm
The application note available at this site explains the filter in more detail. The
example source code and the filter object library are supplied as an OpenVMS
backup save set.
Note that this filter is required only to make certain details of floating point
exceptions conform to the IEEE standard. It is not required for normal floating
point operation.
5.11.2 Ada Event Support (Integrity servers Only)
V8.3
Ada event support (SET BREAK/EVENT=ada_event, where ada_event is one
of the events described by SHOW EVENT) is enabled on OpenVMS Integrity
servers. However, this support is incomplete.
5–10 Programming Release Notes
