Some of the base level improvements over previous releases of AutoCAD on SGI are summarized below. This is in addition to the general feature/performance improvements made across all the R13_c4 platforms. Differential Chip Support ------------------------- The MIPS R4000 (and later) processor contains many instruction set extensions to the MIPS1 instruction set that was defined by the MIPS R2000/R3000. A subset of these instruction set extensions defines the MIPS2 instruction set and is accessible with the -mips2 option. The new features added by the MIPS2 instruction set extensions are: o Double precision floating point load and store instructions. This can provide significant improvement to code using double precision floating point manipulation. A single instruction can load/store a double precision floating point value. In contrast, the R2000/R3000 required using two instructions to reference the upper half and the lower half of the double precision value. o Intrinsic instructions to convert floating point numbers. The new instructions provide truncate, round, ceiling and floor operations. On the R2000/R3000, these instructions were implemented as assembler macros which expanded into approximately 11 instructions. Code which does significant amount of floating point to integer conversions should benefit from the -mips2 option. o Floating point sqrt instruction. This is faster than the sqrt routine in the math libraries for the R2000/R3000. o Branch likely instructions. Every branch instruction in the MIPS1 architecture has a corresponding branch likely form. In this form of the branch, the instruction in the delay slot of the branch is nullified if the conditional branch is not taken. o New compare and trap instructions, which cause an exception to be raised based on the result of comparing two registers or a register and immediate value. In the R2000/R3000, these instructions were implemented as assembler macros which expanded into a sequence using a conditional branch and a break instruction. In testing on a wide range of drawings and operations, an improvement of 12% is observed over R13_c3a. In floating-point specific tasks, the improvement is more like 20-25%. AutoCAD uses double-precision (64-bit) floating point math exclusively. Use of Shared Libraries ----------------------- In R12, all of AutoCAD was built with static libraries, that is, the AutoCAD executable was completely self-contained. In R13_c3a, three shared libraries (DSOs) were used to build AutoCAD. The largest of these was libacis.so (containing the ACIS geometry library). This resulted in an acad binary of about 10MB and the ACIS library of 15MB that needed to be loaded at startup. In R13_c4, 40 smaller DSOs were used to build AutoCAD, none over 4MB and most well under 1MB in size. The size of AutoCAD is now about 3.3MB. Startup time is approx. 1/2 the time observed in R13_c3a. This is mainly due to not having to load all of the code in all the libraries at startup time. Rather, code is loaded only when it is needed. As a side benefit of DSO use, the operation of multiple AutoCAD sessions has improved. Since shared libraries are shareable, multiple AutoCAD sessions can share most of their code. A single AutoCAD session uses about 10MB of memory at startup, a second session consumes an additional 5MB and each additional session after that only requires 1MB per session. Optimized GL display driver --------------------------- The inclusion of an optimized GL display driver provides several advantages: 1. Improved drawing performance on both base level and accelerated graphics hardware. Display is always in TrueColor mode to eliminate color flashing. 2. Eliminates the need for backing store in the Xserver. This increases graphics performance and reduces memory requirements. 3. Uses less memory due to a more efficient display list memory architecture, resulting in 1/3 to 1/6 the memory consumption of the default Motif display driver. 4. Includes a wide range of desktop and collaborative engineering 'hooks': Drag and Drop, Inventor/VRML export, productivity features, (see 'System Integration' below). 5. Support for both the Indigo Magic and the TriTeal CDE desktop environments. Hopefully, this will clarify some of the questions you had regarding the highlights of the R13_c4 port for SGI. System Integration ------------------ Included with the GL display driver are a number of other subsystems that serve to integrate AutoCAD into the Indigo Magic Desktop: - AutoSpool Ties AutoCAD into the Impressario print system. - Inventor export Allows 3D visualization from AutoCAD. - Collaborative engr. Supports group interaction.