VAX Computer Architecture Michael Collins CS350 – Computer Organization Section 1 – Spring 2002

Background Built by Digital Equipment Corporation Introduced in bit architecture One of most popular architectures ever Highly compatible with PDP-11 Rated in VAX Units of Performance Still used today

Data Types Byte was basic unit Not all had to be implemented in a system for it to function 16 types –Byte, word, longword, quadword, octaword, F_floating, D_floating, G_floating, H_floating, variable-length bit field, absolute queues, self-relative queues, character string, trailing numeric string, leading separate numeric string, packed decimal string

Addressing Key point of architecture 32-bit 4.3 billion bytes of virtual address space 9 basic modes –Register, register deferred, autoincrement, autoincrement deferred, autodecrement, displacement, displacement deferred, literal, index

Processor State Portion of a process that is store in the processor’s registers rather than memory while it is executing bit general purpose registers –Base registers, index registers, temporary storage, accumulators, specialized registers 15, program counter 14, stack pointer 13, current frame pointer 12, argument pointer 32-bit Processor status longword 32-bit Internal processor register

Memory Memory manager 4 access modes –Kernel, executive, supervisor, user Page table Virtual address space –System address space, Per-process space

Timeline 1975 – Virtual Address eXtension (VAX) computer architecture is first announced – VAX-11/780 : case is 60” tall by 47” wide; hit MIPS barrier; four megabytes of Random Access Memory (RAM); implemented all instructions, system rated at 1.0VUP – MicroVAX I : case is 22” tall by 6” wide by 28” deep; first VAX to use a true subset implementation; very slow, rated at.3VUP – VAX 8600 : case is 60” tall by 80” wide; implemented all instructions; system rated at 4VUP – MicroVAX II : first single-chip processor; subset instruction implementation; commercially a very popular system; system rated at.9VUP 1986 – VAX 8200 : case is 42” tall by 22” wide; implemented all instructions but not PDP-11 compatibility mode; system rated at 1.2VUP.

Timeline (cont.) 1987 – VAXStation 2000 : very small system; popular for graphic design; system rated at.9VUP – MicroVAX 3500/3600 : first VAX to use CVAX chip; had physical space for 64 megabytes RAM; system rated at 2.7VUP – VAX 9000 : known as a big, hot, expensive, and electricity consuming machine; system rated at 157VUP – VAX 4000 : known as a more robust and useful MicroVAX; supported 512 megabytes RAM; depending upon model, rated from 5- 45VUP – VAX 6000 : first VAX to use Mariah chip; system rated at 72VUP – VAX 7000/10000 : rated at 91MHz – Development of new models ends – Compaq purchases DEC for $9.6 billion – Sales of new systems ends.

Bibliography - Compaq Corporation (2001). “VAX MACRO and Instruction Set Reference Manual.” URL: - Compaq Corporation (Date unknown). “VAX Timeline.” URL: - Haemmerle, Vance (1997). “My other VAX is a VAXBar.” URL: - (Date unknown). “VAX.” URL: - Jones International (1999). “Digital Equipment Corporation (DEC).” URL: - Leonard, Timothy (1987). VAX Architecture Reference Manual. Billerica, MA: DECBooks. QA76.8.V37V : ISBN X - Pyramid Technology Services. (Date unknown). “VAX VUP Comparison Chart.” URL: - Silverman, Dwight. “Compaq Buys Digital, Rises to Industry’s Top 3.” Houston Chronicle. 27 January URL: