Hi ,
I looking for a simple (ASM) routine to convert BFP (8bytes)
to binary Word .
I read POPs about it , but found explanation not clear enough .
TIA

Excuse me, but what is BFP?
And 8 bytes are 64 bits, a "word" in S/370 is 32 bits. What kind of
conversion do you want?

Sven

Binary Floating Point. Same as IEEE floating point. Not the same as HFP (Hex
Floating Point) -- the scheme originally used on IBM mainframes.

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So BFP is not understood by the floating point feature on IBM S/370?

I frankly do not understand the purpose of having data on a platform in
a format not understood on that platform, but once you know what you
want to do and the format of the data involved it should not be much of
a task to write a conversion routine?

What you need seems to be just a precise definition of your BFP format?

Sven

The hardware to handle BFP has been been available for a few years
now. The first POP I see mentioning it is in the bookshelf for OS/390
2.8, circa 1999.

The POP has that. The problem of converting long BFP to 32 bit binary is
what to do about values that don't convert? Do you truncate past the
decimal point? What about values that are beyond +/- 2G (for signed
binary)? If there is such a routine for HFP, then that could be used by
first converting the BFP number to HFP (a single instruction).

A very nice essay on IEEE floating point and the decisions made on how
to implement on S/390 (and z/Arch of course) is here:

http://www.research.ibm.com/journal/rd/435/abbott.html

BFP support has been generally available to programmers since September
1998 (almost 5 years ago). Beginning with OS/390 V2R6, the operating
system provides a) support for BFP-capable S/390 hardware (saving all 16
FP registers across interrupts, etc.) and b) an instruction simulator
that provides support for the instructions when running on a machine
without the hardware feature. The first machines with BFP hardware
support were the G5s. However, because of the software simulation, any
program exploiting BFP is *guaranteed* to work correctly under OS/390
V2R6 or higher.

The CVTBFP flag in the CVT indicates BFP support is present in the
operating system. CVTBFPH indicates BFP support is available in the
hardware.

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 -----------------------------------------------------------------
| Edward E. Jaffe                |                                |

| Phoenix Software International | Tel: (310) 338-0400 x318       |
| 5200 W Century Blvd, Suite 800 | Fax: (310) 338-0801            |
| Los Angeles, CA 90045          | http://www.phoenixsoftware.com |
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