Origin of the Name • Mini-minor Mini-Computers • Mini-skirt • DEC Europe sales person Yaniv Frishman Seminar in computer History CS236801 1 Seminar in computer History CS236801 2 Comparison with Main-Frames Defining Facets Mainframes: 1. Architecture • Leased (rented) 2. Packaging • HW modifications not allowed • HW & SW sold together 3. Role of third-party in apps development Minicomputers: 4. Price • Sold, not rented 5. Financing • Much cheaper • Open spec, modifications encouraged • OEM model Seminar in computer History CS236801 3 Seminar in computer History CS236801 4 Word Length Short Word Workarounds • Typical 1960s IBM Mainframes used 36- • More complex instructions bits – Address stored in a different register – 10 decimal digits • Using double precision math (add with • Manufacturers assumed less would not be carry) enough • Shorter instructions reduce addressing abilities Seminar in computer History CS236801 5 Seminar in computer History CS236801 6 1 DEC PDP-1 PDP-1 I/O - DMA • I/O flows directly from the device to memory • Included many of the TX-0 features • Multiple interrupts • Designed from the ground using • HW support for correct handling (priority) transistors • Cheap: a single IBM I/O channel cost more • Capable of 100,000 additions per second than a complete PDP-1 ($120K) • Core memory of 4K words • About 50 machines sold Seminar in computer History CS236801 7 Seminar in computer History CS236801 8 PDP-1 Space Invaders PDP-1 Space Invaders • Developed by MIT students Applet demo – see • Using 1024x1204 CRT http://spacewar.oversigma.com/ • Planet Map • Simulated Gravity Seminar in computer History CS236801 9 Seminar in computer History CS236801 10 Business Model / DEC openness Interaction with Customers • IBM rented its computers • Encouraged modification by the customers – Modifications need IBM approval • Published detailed specs on cheap paper • DEC model: • Didn’t develop specialized HW and SW – PDP-1 was sold, not leased Seminar in computer History CS236801 11 Seminar in computer History CS236801 12 2 DEC PDP-8 PDP-8 Addressing • 7bits were used for the address field (small) • Memory: 32 blocks of 128 words (4KW) • 12 bit word length • Access across a block achieved by • 50,000 computers installed • Successful - performance, storage, packaging, setting bits in the opcode price • Improvements in logic and core memory reduced the cycle time to 1.6 microsec. Seminar in computer History CS236801 13 Seminar in computer History CS236801 14 PDP8 packaging PDP8 pricing • Constructed from a series of • Very cheap: $18K compact modules • Price dropped to $10K after a few years – Each performed a specific function • Price shocked the industry, many orders • Modules plugged into a chassis • Wire wrap connection • Once again estimates of the computer market size were proved incorrect • Small: embedded in other equipment • 8 cubic feet (volume), 250 pounds Seminar in computer History CS236801 15 Seminar in computer History CS236801 16 PDP8 programming OEMs • OEM: a separate company that bought • Limited memory prevented high-level minicomoputers, added specialized HW & programming SW and sold them under their own label • Simple, easy to understand computer • Relieved DEC of developing specialized SW • Gave rise to OEMs • Ranged across all segment of society: – Medical instrumentation – Small business records – Industrial controllers Seminar in computer History CS236801 17 Seminar in computer History CS236801 18 3 OEM example DEC PDP-10 • LS-8 used to operate theatrical stage lighting • One of the most influential computers • Cited as a key element in the success of the • The machine that made time-sharing common Broadway hit “A Chorus Line” – The basis of the ARPANET • Contained a PDP-8A, introduced 1975 – The platform upon which many applications were • Application specific control panel first developed: • EMACS • TeX • ISPELL • Kermit Seminar in computer History CS236801 19 Seminar in computer History CS236801 20 PDP-10 Architecture KA-10 • An improved HW implementation of the • The original PDP-10 processor was the PDP-6 KA10 • Shared the same 36-bit word length • Slightly extended the instruction set Seminar in computer History CS236801 21 Seminar in computer History CS236801 22 Wire Wrap Backplane PDP-10 Memory Management • Backplanes wire wrapped, semi- • KA10: maximum main memory of 256 automated manufacturing process Kwords • Management consisted of 2 sets of protection & relocation registers -"base and bounds" registers • This allowed separate read-only shareable code segment and read-write data/stack segment Seminar in computer History CS236801 23 Seminar in computer History CS236801 24 4 PDP-11 PDP-11 Instruction Set • A successor to the PDP-8 • A highly-orthogonal instruction set: • Was easier to program than its Operation ; operand access mode predecessors • Any addressing mode would work with any • the world's most successful family of operation minicomputers • Was replaced by VAX-11 Seminar in computer History CS236801 25 Seminar in computer History CS236801 26 PDP-11 I/O • New architecture: no dedicated I/O bus • It had only a memory bus, the Unibus DEC VAX • I/O devices are memory mapped Minicomputers – No need for special I/O instructions • Four levels of interrupts • Interrupting device puts its address on the bus Seminar in computer History CS236801 27 VAX - a virtual memory VAX computer • Making small but fast main memory seem • An extension of the PDP-11, with mainframe to be bigger by swapping data from a performance performance slower disk • Design began 1974 • Overall performance not seriously • VAX = Virtual Address eXtension (of PDP-11) degraded • VAX was able to execute PDP-11 instructions in a 32 instead of 16-bit address space • User is not aware that swapping is done • PDP-11 compatibility bit that was later dropped • The VAX provided a 32-bit virtual address • Memory divided into pages Seminar in computer History CS236801 29 Seminar in computer History CS236801 30 5 VAX Instruction Set VAX Commercial Aspects • Sixteen general purpose 32-bit registers • Successful: 100,000 units in 10 years • Rich set of 250 instructions • General purpose computer that came with • Two and three operand formats standard languages and SW • Register or memory operand in most • Biggest impact in engineering and science instructions • Prices started at $120K • The quintessential CISC processing • Cheap enough to serve a division in the architecture aerospace, automotive, chemical firms Seminar in computer History CS236801 31 Seminar in computer History CS236801 32 MIPS • The performance of VAX 11/780 became known as MIPS (million instructions per second) A Brief VAX Timeline • Later used as a benchmark of performance Seminar in computer History CS236801 33 VAX Kickoff First VAX • The VAX Architecture Committee began • VAX-11/780 introduced work on a computer with 32-bit architecture • Image: inside of VAX-11/780 Seminar in computer History CS236801 35 Seminar in computer History CS236801 36 6 VAX OS LSI VAX • V1.0 of the VMS operating system ships • Introduction of the VAX-11/750 • FORTRAN IV and DECnet, a 64 megabyte • The industry's first Large Scale Integration memory limit, an event driven priority (LSI) 32-bit minicomputer scheduler, process swapper, process deletion/creation/control Seminar in computer History CS236801 37 Seminar in computer History CS236801 38 ECL VAX “Personal “ VAX • VAX 8600: the first VAX implementation in • VAX station I. ECL technology • A powerful, single-user computing system supporting the professional user Seminar in computer History CS236801 39 Seminar in computer History CS236801 40 VLSI VAX VAX Station Best-Seller • MicroVAX: VAX on a VLSI chip • The VAXStation 2000 is introduced. • DIGITAL's first workstation with a cost of less than $5,000 • Became the highest volume workstation in the industry Seminar in computer History CS236801 41 Seminar in computer History CS236801 42 7 Last VAX Summary • VAX 7000 series, DIGITAL's most • Computer class between big-iron powerful VAX system, field-upgradeable to mainframes and personal computers the Alpha 64-bit processor • The basis for nowadays servers (VAX) • Continuing trend of bringing the computer to more people • Introduced important architectural aspects Seminar in computer History CS236801 43 Seminar in computer History CS236801 44 References References • WikiPedia • House of VAX: • A History of MTS - http://www.mcmanis.com/chuck/computers/vaxe http://www.clock.org/~jss/work/mts/30years.html n/ • Batch VS TS – Bruce Lakin, NJ EDU Computer • VAX timeline: Network 1980. http://research.microsoft.com/~gbell/digital/timeli • A History of Modern Computing by Paul E Ceruzzi. ne/32-bit.htm • The McGraw-Hill Computer Handbook • PDP-10: • IEEE Annals of the History of Computing http://www.columbia.edu/acis/history/pdp10.html • 234120 - Operating Systems – CS Technion • http://webcourse.cs.technion.ac.il/234118/ • www.computerhistory.org Seminar in computer History CS236801 45 Seminar in computer History CS236801 46 References • http://history.sandiego.edu/GEN/recording/ computer1.html • http://www.old- computers.com/history/detail.asp?n=58&t= 4 • http://www.poetproductions.com • http://www.ibiblio.org/pub/academic/comp uter-science/history/pictures/pdp1_1.jpg • http://spacewar.oversigma.com/ Seminar in computer History CS236801 47 8.