For more information about cryptographic functions on z14 servers, see Chapter 6, “Cryptographic features” on page 207. 

## 3.4.6 Decimal floating point accelerator 

The decimal floating point (DFP) accelerator function is present on each of the microprocessors (cores) on the 10-core chip. Its implementation meets business application requirements for better performance, precision, and function. 

Base 10 arithmetic is used for most business and financial computation. Floating point computation that is used for work that is typically done in decimal arithmetic involves frequent data conversions and approximation to represent decimal numbers. This process makes floating point arithmetic complex and error-prone for programmers who use it for applications in which the data is typically decimal. 

Hardware DFP computational instructions provide the following features: 

GLYPH<SM590000> Data formats of 4, 8, and 16 bytes 

GLYPH<SM590000> An encoded decimal (base 10) representation for data 

GLYPH<SM590000> Instructions for running decimal floating point computations 

GLYPH<SM590000> An instruction that runs data conversions to and from the decimal floating point representation 

## Benefits of the DFP accelerator 

The DFP accelerator offers the following benefits: 

GLYPH<SM590000> Avoids rounding issues, such as those that happen with binary-to-decimal conversions. 

GLYPH<SM590000> Controls existing binary-coded decimal (BCD) operations better. 

GLYPH<SM590000> Follows the standardization of the dominant decimal data and decimal operations in commercial computing, supporting the industry standardization (IEEE 745R) of decimal floating point operations. Instructions are added in support of the Draft Standard for Floating-Point Arithmetic - IEEE 754-2008, which is intended to supersede the ANSI/IEEE Standard 754-1985. 

GLYPH<SM590000> Allows COBOL programs that use zoned-decimal operations to take advantage of the z/Architecture DFP instructions. 

z14 servers have two DFP accelerator units per core, which improve the decimal floating point execution bandwidth. The floating point instructions operate on newly designed vector registers (32 new 128-bit registers). 

z14 servers include new decimal floating point packed conversion facility support with the following benefits: 

GLYPH<SM590000> Reduces code path length because extra instructions to format conversion are no longer needed. 

GLYPH<SM590000> Packed data is operated in memory by all decimal instructions without general-purpose registers, which were required only to prepare for decimal floating point packed conversion instruction. 

GLYPH<SM590000> Converting from packed can now force the input packed value to positive instead of requiring a separate OI, OILL, or load positive instruction. 

GLYPH<SM590000> Converting to packed can now force a positive zero result instead of requiring ZAP instruction. 

