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52-571: Like the cosmetically similar Rainbow 100 and DECmate II (also introduced at that time), the PRO series uses the LK201 keyboard and 400KB single-sided quad-density floppy disk drives (known as RX50), and offers a choice of color or monochrome monitors. For DEC, none of the three would be favorably received, and the industry instead standardized on Intel 8088 -based IBM PC compatibles which are all binary program compatible with each other. In some ways,

104-470: A TTL 15 kHz composite-video signal compatible with RS-170 (NTSC) in monochrome mode. With the inclusion of the graphics option, the Rainbow could also output sync-on-green RGB video signals at TTL levels. The Rainbow was most often coupled with the 12-inch VR201 monochrome monitor or the 13-inch VR241 color monitor, both produced by Digital Equipment Corporation . The Rainbow was unique, in that

156-730: A good job at emulating the IBM BIOS, its inability to trap references to the video and other hardware limited what would run on the Rainbow. The FOSSIL TSR allowed several terminal programs and editors to run on the IBM-PC, Rainbow, and other early 8088/8086 computers, but its limited adoption hampered its usefulness. Various other hacks allowed popular programs such as Turbo Pascal and Turbo C to run. Such patches circulated, but new releases made these difficult to keep up with, and over time these hacks dried up (the online archives have very little new after 1991 or 1992, although some of that may be due to

208-443: A hard disk. Other distinguishing hardware features included the three 2764 (8 KB) ROM chips holding the system firmware and the case fan/power supply combinations. In addition, the 100A was unable to move its hardware interrupt vectors to avoid the conflict with MS-DOS soft INT 21, etc. DOS had to take unusual actions to distinguish between the hard and soft vectors. The Rainbow 100A initially only supported 256 KB of RAM total, but

260-673: A hard-disk option was installed on the Rainbow, the kit included the 100+ emblem for the computer's case. The Rainbow contained two separate data buses controlled by the Zilog Z80 and the Intel 8088 respectively. The buses exchanged information via a shared 62 KB memory. When not executing 8-bit code, the Zilog Z80 was used for floppy disk access. The 8088 bus was used for control of all other subsystems, including graphics, hard disk access, and communications. While it may have been theoretically possible to load Z80 binary code into

312-535: A listing of Microsoft assembly code to handle this. The theory was that hardware interrupts would interrupt again but software interrupts would only happen once. The Rainbow 100B fixed this overlap in hardware by changes to the board design that allowed the OS to move the hardware interrupts. This means that the MS-DOS 3.10b version for the Rainbow can only run on the Rainbow 100B. DEC itself ported Microsoft Windows 1.0 to

364-552: A menu-driven core user interface. Industry critics complained that this user interface was awkward, slow, and inflexible, offering few advantages over the command-line based MS-DOS user interface that was coming into widespread use. Other available operating systems include DEC RT-11 , VenturCom Venix , and 2.9BSD Unix . Later, the Professional 380 ( PRO-380 ) was introduced using the much faster J-11 chip set (as used in 11/73 systems). However, due to clocking issues on

416-496: A new BBS platform that ran on DOS, they learned of FidoBBS and arranged to have its developer port the serial drivers to the Rainbow platform. This ran up considerable phone bills sending emails and file transfers between St. Louis and the developer in San Francisco , and the developer produced FidoNet as a method of automating exchanges late at night when phone rates were lower. Piers Anthony wrote many of his books from

468-434: A number of expansion slots that could be used for a single purpose only: extra memory, graphics, rx-50 floppy controller. One slot was originally designed for a DMA enabled serial card, but hard disk controllers were used there instead because DEC bet wrong on which was more important. Univation produced an Ethernet card that could boot the Rainbow over the network for that slot. It stacked to allow both hard disk and Ethernet in

520-607: A number of sources including The Rainbow runs the CP/M-86/80 operating system, which detects whether software is written for 16-bit CP/M-86 or 8-bit CP/M-80 and runs it on the appropriate processor. DEC later released a compatible version of MS-DOS, but little DOS software was released on Rainbow media. While it provided the same MS-DOS functions as IBM's PC DOS , it lacked the IBM PC's video and keyboard ROM BIOS interface which most MS-DOS software relied upon, limiting

572-572: A programmable peripheral interface (PPI) consisting of three 8-bit ports for transferring data, address, and control signals between the console and the VAX console interface. The Pro had highly advanced graphic capabilities for its time. The graphic card for the Pro 325/350 has 32 KB of RAM and can display two-color screens at either 1024x240@60Hz or 1024x256@50Hz. It can also display 512 pixels per line when each pixel has 4 levels of intensity. The other option

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624-580: A scientific workstation, where the market was also headed to Intel 8086 , or alternately to Motorola 68000 -based computers. The failure of DEC to gain a significant foothold in the high-volume PC market would be the beginning of the end of the computer hardware industry in New England, as nearly all computer companies located there were focused on minicomputers for large organizations, from DEC to Data General , Wang , Prime , Computervision , Honeywell , and Symbolics Inc. The PRO-325 and -350 use

676-411: A significant foothold in the high-volume PC market would be the beginning of the end of the computer hardware industry in New England, as nearly all computer companies located there were focused on minicomputers for large organizations, from DEC to Data General , Wang , Prime , Computervision , Honeywell , and Symbolics Inc. The Rainbow came in three models, the 100A, 100B and 100+. The "A" model

728-451: A single drive with up to 8 heads and 1024 cylinders , limiting storage to a maximum of 67 MB . Third-party hard-disk controllers were also available, including a dual winchester support from CHS The base Rainbow system was capable of displaying text in 80×24- or 132×24-character format in monochrome only. The system could apply attributes to text including bolding, double-width, and double-height-double-width. The graphics option

780-622: A small but important role in the creation of the FidoNet system. A computer club in St. Louis was in the process of setting up a BBS system using CBBS on CP/M when they learned that DEC would be giving the club a Rainbow 100 for free. The group planned on starting the BBS on this machine as soon as it arrived; but, when it did, they found that the Z80 did not have access to the serial ports. Casting about for

832-712: A total 892 KB for the 100B or 828 KB for the 100A. The difference in max memory was due to the difference in initial memory configuration. The floppy disk drives, known as the RX50 , accepted proprietary 400 KB single-sided, quad-density 5¼-inch diskettes . Initial versions of the operating systems on the Rainbow did not allow for low-level formatting, requiring users to purchase RX50 media from Digital Equipment Corporation . The high cost of media ($ 5 per disk) led to accusations of vendor "lock-in" against Digital. However, later versions of MS-DOS and CP/M allowed formatting of diskettes. Formatting software for "normal" diskettes

884-420: Is 256 pixels per line when each pixel has 16 levels of intensity. The standard software only uses the 1024x240 mode. Moreover the standard software uses only 960 pixels out 1024. To display colors, an additional card should be installed, which adds 64 KB of RAM. This card enables to display 8 colors per pixel using a 256-color palette. This is mapped mode. The standard software uses only this mode. However it

936-515: Is a microcomputer introduced by Digital Equipment Corporation (DEC) in 1982. This desktop unit had a monitor similar to the VT220 and a dual-CPU box with both 4 MHz Zilog Z80 and 4.81 MHz Intel 8088 CPUs. The Rainbow 100 was a triple-use machine: VT100 mode (industry standard terminal for interacting with DEC's own VAX ), 8-bit CP/M mode (using the Z80), and CP/M-86 or MS-DOS mode using

988-404: Is possible to use the unmapped graphic mode when each graphic plane provides intensity for its base color. This allows 4096 colors to be displayed simultaneously when 256 pixels are displayed per line, or 64 colors when 512 pixels are displayed per line. The Pro 380 graphics is more advanced. The standard graphic card is integrated into the motherboard. The card has 128 KB of memory. This enables

1040-558: The '80s on his DEC Rainbow. The DEC Rainbow can be seen in the films Ghostbusters , Beverly Hills Cop , and Firestarter . Michael Paré watches a TV commercial for "The Rainbow" in The Philadelphia Experiment . DEC J-11 The J-11 is a microprocessor chip set that implements the PDP-11 instruction set architecture (ISA) jointly developed by Digital Equipment Corporation and Intersil . It

1092-473: The 8088. It ultimately failed to succeed in the marketplace which became dominated by the simpler IBM PC and its clones which established the industry standard as compatibility with CP/M became less important than IBM PC compatibility. Writer David Ahl called it a disastrous foray into the personal computer market. The Rainbow was launched along with the similarly packaged DEC Professional and DECmate II which were also not successful. The failure of DEC to gain

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1144-648: The F-11 chipset (as used in LSI-11/23 systems) to create a single-board PDP-11 with up to six expansion slots of a proprietary CTI (Computing Terminal Interconnect) bus using 90-pin ZIF connectors. The PRO family uses dual RX50 floppy drives for storage; the PRO-325 has only floppies, and the 350 and 380 also include an internal hard drive. Mainline PDP-11s generally use separate serial terminals as console and display devices;

1196-624: The PC outperformed the same operating system on the DEC Professional and PDP-11/23. Further, although the PDP-11 was a very successful minicomputer, it lacked a wide base of affordable small business software. By comparison, many existing CP/M applications (see the Rainbow 100 ) were easily ported to the similar 8086/8088 chips and MS-DOS operating system. Porting existing PDP-11 software to

1248-479: The PDP-11 microprocessors are technically superior to the Intel-based chips. While the 8088 is restricted to 1MB of memory because of its 20-bit address bus, DEC microprocessors are capable of accessing 4MB with their 22-bit addressing (although direct addressing of memory is limited in both approaches to 64KB segments, limiting the size of individual code and data objects). BYTE in 1984 reported that Venix on

1300-435: The PRO family uses built-in bit-mapped graphics to drive a combined console and display. All other I/O devices in the PRO family are also different (in most cases, radically different) from their counterparts on other PDP-11 models. For example, while the internal bus supports direct memory access (DMA), none of the available I/O devices actually use this feature. The interrupt system is implemented using Intel PC chips of

1352-402: The PRO was complicated by design decisions that rendered it partially incompatible with its parent product line. Industry critics observed that this incompatibility appeared at least in part deliberate, as DEC belatedly sought to "protect" its more-profitable mainstream PDP-11s from price competition with lower-priced PCs. The PRO was never widely accepted as an office personal computer, nor as

1404-494: The RABIT TSR, which solved the problem generically for all Borland products). The DEC Rainbow 100 MS-DOS did support FAT formatted floppies. They were FAT12 format on 80-track, single-sided, quad-density 5.25" drives. The first two tracks were reserved for the boot loader, but didn't contain an MBR nor a BPB (MS-DOS 2.x and 3.10 on the Rainbow used a static in-memory BPB instead). The boot sector (track 0, side 0, sector 1)

1456-550: The Rainbow 100. Rock Point Community School on the Navajo reservation in Arizona commissioned a ROM chip for the Navajo language, enabling the school to create bilingual computer programs. Univation produced a number of products for the Rainbow as well. They offered add-in memory cards, hard disk controllers and LAN cards. The Univation disk interface was SASI/SCSI-1, but not software compatible with DEC's Winchester Disk option. It

1508-522: The Rainbow to execute alongside 8088 code, this procedure has never been demonstrated. The 8088 could be upgraded to the faster NEC V20 chip. This gave about 10-15% speed improvement, but required changes to the system's ROMs to fix two timing loops. The 100A model shipped with 64 KB memory on the motherboard, while the 100B had 128 KB memory on the motherboard. Daughterboards were available from Digital Equipment Corporation that could increase system memory with up to an additional 768 KB for

1560-481: The Rainbow. There was an "ACT Winchester Option" available in Australia for which drivers have recently surfaced. Duncan MacDonald, Inc. offered a 20MB Floppy tape cartridge using a rebranded Cipher Data Products Model 525 floppy-tape cartridge tape drive. It used 3M DC600A tapes and could back up a 20MB RD31 in about 30 minutes. It included software to backup MS-DOS, CP/M and CCP/M partitions. List price in 1987

1612-448: The Rainbow. The Suitable Solutions Turbow-286 board could run a modified version of Windows 3.0 . Software bundled with DEC Rainbow floor model included: These documents come in booklets contained inside two hard case boxes, with the DEC logo. The Rainbow used a distinct version of MS-DOS, so it was not completely software- or hardware-compatible with the IBM PC or PC DOS. The expectation

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1664-476: The VT220 style of this keyboard can clearly be seen in the layout of the enhanced 101-key keyboard adopted by IBM in 1985. Third-party upgrades were also available, including an 80286 (286) processor upgrade (Turbow-286), a 3.5-inch disk adapter kit (IDrive), and a battery-backed clock chip (ClikClok), all from Suitable Solutions . In 1984, the first computer support for Native American languages began with

1716-464: The boot screen language and keyboard layout, eliminating the need to switch ROM. The "B" model also allowed remapping of hardware interrupts to be more compatible with MS-DOS. The B model also improved the memory expansion slot to allow a maximum configuration of 892 KB. The "100+" model was actually a marketing designation signifying that the system shipped with a hard drive installed; the "100+" and "B" models were identical in all other respects. When

1768-457: The boot screen. On the 100A, the ROMs only supported three languages. The Rainbow did not have an ISA bus, so the typical 640 KB RAM limit didn't apply, with both models supporting a maximum RAM of over 800 KB . The "A" model was the first produced by Digital. The distinguishing characteristic of the "A" model from an end-user perspective was that the earlier firmware did not support booting from

1820-509: The commercial software that could be run. Towards the end of the Rainbow's life, users were able to run some IBM PC-compatible MS-DOS software using an emulation application called Code Blue , though it emulated only the IBM PC's BIOS and some of the hardware, so programs that accessed the video cards directly would not work very well. MS-DOS compatibility was added late in the design, so hardware interrupts and MS-DOS software interrupts overlapped. One DEC documentation pack for developers included

1872-536: The disk. This was remedied later by placing a red arrow on the diskette slots and on the top of the diskettes to indicate which side of the diskette to be inserted into each diskette drive. Digital Equipment Corporation produced a Winchester disk controller capable of controlling hard disks compatible with the ST-506 interface. The controller, based on the Western Digital WD1010 chip, was limited to

1924-575: The limitation in the memory expansion slot was later worked around with a special adapter card, though the maximum was limited to 828 KB. The "B" model followed the "A" model, and introduced a number of changes. The "B" model featured the ability to boot from a hard disk (referred to as the Winchester drive) via the boot menu due to updated firmware. The hardware changes included bigger firmware stored on two 27128 (16 KB) ROMs and an improved case fan/power supply. The firmware allowed selection of

1976-608: The motherboard, the J-11 chip runs at 10 MHz instead of 16-18 MHz, thus making the PRO-380 slower than a stock 11/73 system. The DEC Professional Series PC-38N is a PRO-380 with a real-time interface (RTI) that is used as the console for the VAX 8500 and 8550 . The RTI has two serial line units: one connects to the VAX environmental monitoring module (EMM) and the other is a spare that can be used for data transfer. The RTI also has

2028-437: The physical sectors in order numbered 1 to 10 on each track after the reserved tracks, but the logical sectors from 1 to 10 were stored in physical sectors 1, 6, 2, 7, 3, 8, 4, 9, 5, 10. This makes it hard to create Rainbow disk images since all existing tools assume there will be an MBR with a BPB, and required various hacks to make up for the lack of on-disk BPB. The DEC Rainbow 100 had no general expansion bus. Instead, it had

2080-407: The power for the monochrome monitor was supplied through the single video cable, eliminating the need for a separate power cable. The Rainbow 100 and the other two microcomputers which DEC announced at the same time ( DECmate II and Pro-350 ) had two quirks that annoyed conservative users. The LK201 keyboard used a new layout that made some Teletype Model 33 and VT100 users unhappy. However,

2132-509: The same box, but it cost $ 750 which was prohibitively expensive so few Rainbows had Ethernet. While the software incompatibilities were bad, the lack of expansion hardware flexibility was worse, and the inability to use ISA cards, despite their flaws at the time, played a significant role in the Rainbow fading from the scene. The Multi Emulator Super System can run the Rainbow-specific Windows 1.0. The Rainbow 100 played

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2184-427: The time, which again makes it very different from the PDP-11 standard interrupt architecture. For all these reasons, support of the PRO family requires extensive modifications to the previously-existing operating system software, and the PRO cannot run standard PDP-11 software without modification. The default PRO-3xx operating system is DEC's Professional Operating System ( P/OS ), a modified version of RSX-11 M with

2236-632: The use of interlaced modes, which double the vertical resolution. The optional color supplement card adds 256 KB of RAM. The Pro 380 color graphics enables the use of 4096 palette colors in mapped mode. The Pro 380 can hold 4 uninterlaced pictures or 2 interlaced in its video RAM. Like the PDP-8 and PDP-11 before it, the Professional 350 was cloned by Elektronika in the Soviet Union . Other PDP-11 clones: Rainbow 100 The Rainbow 100

2288-424: Was $ 1200. In addition, Duncan MacDonald, Inc. provided MFM disks in 20MB, 40MB, and 67MB that used the same disks that DEC sold for much more, and provided a nice steel cabinet with power supply so the Rainbow's power supply wouldn't be overtaxed by the power requirements of larger disks. Here are the various hardware options that were available for the Rainbow (country kits are not yet listed): Data compiled from

2340-548: Was Z80 code beginning with DI 0xF3 . The 8088 bootstrap was loaded by the Z80. Track 1, side 0, sector 2 starts with the Media/FAT ID byte 0xFA . Unformatted disks use 0xE5 instead. The file system starts on track 2, side 0, sector 1. There are 2 copies of the FAT and 96 entries in the root directory. In addition, there is a physical to logical track mapping to effect a 2:1 sector interleaving. The disks were formatted with

2392-597: Was a high-end chip set designed to integrate the performance and features of the PDP-11/70 onto a handful of chips. It was used in the PDP-11/73 , PDP-11/83 and Professional 380 . It consisted of a data path chip and a control chip in ceramic leadless packages mounted on a single ceramic hybrid dual inline package (DIP). The control chip incorporated a control sequencer and a microcode ROM. An optional separate floating-point accelerator (FPA) chip could be used, and

2444-422: Was a user-installable module that added graphics and color display capabilities to the Rainbow system. The Graphic module was based on a NEC 7220 graphic display controller (GDC) and an 8×64 KB DRAM video memory. Due to the design of the graphics system, the Rainbow was capable of controlling two monitors simultaneously, one displaying graphics and another displaying text. The base Rainbow system generates

2496-411: Was also made available by third parties. Of note was the single motor used to drive both disk drives via a common spindle, which were arranged one on top of the other. That meant that one disk went underneath the first but inserted upside-down. This earned the diskette drive the nickname "toaster". The unusual orientation confused many first-time users, who would complain that the machine would not read

2548-462: Was based on a design by Xebec . C.H.S. created a dual-Winchester controller for the DEC Rainbow as well. It was compatible enough with the DEC's disk controller that one could boot off it on the 100B/100+/190. Like DEC's offering, it was based on Western Digital's WD1010 chip. However, additional drivers were needed to access the second hard drive. REC of Switzerland created a SCSI card for

2600-549: Was for programs to target the MS-DOS interface and not the underlying hardware. However, many significant commercial software products were writing directly to the hardware for a variety of reasons, including performance. After the Compaq Portable and other clones, the market expectation was that all MS-DOS versions would be fully IBM PC compatible . Later, Microsoft would stop licensing distinctive OEM versions and sell standardized MS-DOS 5.0 at retail. While "Code Blue" did

2652-542: Was packaged in a standard DIP. The data path chip and control chip were fabricated by Intersil in a CMOS process while the FPA was fabricated by Digital in their " ZMOS " NMOS process. The design originally was intended to support multiple control chips to allow implementation of additional instructions such as the Commercial Instruction Set (CIS), but no such control chips were ever offered. A clone of

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2704-414: Was the first released, followed later by the "B" model. The most noticeable differences between the two models were the firmware and slight hardware changes. The systems were referred to with model numbers PC-100A and PC-100B respectively; later "B" models were also designated PC-100B2 . The system included a user-changeable ROM chip in a special casing to support their keyboard layout and language of

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