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71-571: Up until the mid-1990s, mainframes were very large machines that often occupied entire rooms. The rooms were often air conditioned and had special power arrangements to accommodate the three-phase electric power required by the machines. Modern mainframes are now physically comparatively small and require little or no special building arrangements. IBM had demonstrated use of a mainframe instruction set in their first desktop computer—the IBM 5100 , released in 1975. This product used microcode to execute many of

142-454: A diode bridge . A "delta" (Δ) connected transformer winding is connected between phases of a three-phase system. A "wye" (Y) transformer connects each winding from a phase wire to a common neutral point. A single three-phase transformer can be used, or three single-phase transformers. In an "open delta" or "V" system, only two transformers are used. A closed delta made of three single-phase transformers can operate as an open delta if one of

213-415: A high-leg delta supply is sometimes used where one winding of a delta-connected transformer feeding the load is center-tapped and that center tap is grounded and connected as a neutral as shown in the second diagram. This setup produces three different voltages: If the voltage between the center tap (neutral) and each of the top and bottom taps (phase and anti-phase) is 120  V (100%), the voltage across

284-630: A page cache for VM. A November 1985 Computerworld article noted that the machine was "slow selling". The AT/370 was discontinued alongside the XT/370 in April 1987. In April 1988, IBM introduced a System/370 workstation that had been shipping to some customers since August 1987. Officially called the IBM 7437 VM/SP Technical Workstation (and later also known as the Personal System/370), it

355-418: A solid-state drive (SSD). The operating system keeps a page cache in otherwise unused portions of the main memory (RAM), resulting in quicker access to the contents of cached pages and overall performance improvements. A page cache is implemented in kernels with the paging memory management, and is mostly transparent to applications. Usually, all physical memory not directly allocated to applications

426-479: A $ /MIPS basis; for example, an IBM 4341 delivered 1.2 MIPS for $ 500,000 . While it theoretically reduced demand on customers' mainframes by offloading load onto the smaller computer, as customers purchased more XT/370s they likely increased the overall load on the mainframes, increasing IBM's mainframe sales. Similarly to the mainframe version of VM/CMS , the VM/PC also created the illusion of virtual disks , but on

497-420: A four-wire secondary and a three-wire primary, while allowing unbalanced loads and the associated secondary-side neutral currents. Wiring for three phases is typically identified by colors that vary by country and voltage. The phases must be connected in the correct order to achieve the intended direction of rotation of three-phase motors. For example, pumps and fans do not work as intended in reverse. Maintaining

568-456: A grounding transformer (usually a zigzag transformer ) may be connected to allow ground fault currents to return from any phase to ground. Another variation is a "corner grounded" delta system, which is a closed delta that is grounded at one of the junctions of transformers. There are two basic three-phase configurations: wye (Y) and delta (Δ). As shown in the diagram, a delta configuration requires only three wires for transmission, but

639-413: A load can be connected from phase to neutral. Distributing single-phase loads among the phases of a three-phase system balances the load and makes most economical use of conductors and transformers. Page cache In computing, a page cache , sometimes also called disk cache , is a transparent cache for the pages originating from a secondary storage device such as a hard disk drive (HDD) or

710-713: A paper to the Royal Academy of Sciences in Turin . Two months later Nikola Tesla gained U.S. patent 381,968 for a three-phase electric motor design, application filed October 12, 1887. Figure 13 of this patent shows that Tesla envisaged his three-phase motor being powered from the generator via six wires. These alternators operated by creating systems of alternating currents displaced from one another in phase by definite amounts, and depended on rotating magnetic fields for their operation. The resulting source of polyphase power soon found widespread acceptance. The invention of

781-410: A result, larger amounts of main memory bring performance improvements as more data can be cached in memory. Separate disk caching is provided on the hardware side, by dedicated RAM or NVRAM chips located either in the disk controller (in which case the cache is integrated into a hard disk drive and usually called disk buffer ), or in a disk array controller , such memory should not be confused with

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852-413: A set of three AC electric currents , one from each coil (or winding) of the generator. The windings are arranged such that the currents are at the same frequency but with the peaks and troughs of their wave forms offset to provide three complementary currents with a phase separation of one-third cycle ( 120° or 2π ⁄ 3 radians ). The generator frequency is typically 50 or 60 Hz , depending on

923-685: A single CMOS main processor (performance about 8 MIPS) are used; the S/390 CPU used in the Integrated Server is in fact the P/390 E-card. A Pentium II is used as IOSP (I/O Service Processor). It supports four ESCON and to four parallel channels. Standard PCI and ISA slots are present. A maximum of 255 GB internal harddisks are supported (16x 18GB HDs, with 2x HDs for redundancy). The supported OSs are OS/390, MVS/ESA, VM/ESA and VSE/ESA. Fujitsu offers two based systems that make up

994-523: A waterfall at a distance was explored at the Grängesberg mine. A 45  m fall at Hällsjön, Smedjebackens kommun, where a small iron work had been located, was selected. In 1893, a three-phase 9.5  kV system was used to transfer 400 horsepower (300 kW) a distance of 15 km (10 miles), becoming the first commercial application. In a symmetric three-phase power supply system, three conductors each carry an alternating current of

1065-414: A wye (star) configuration may have a fourth wire. The fourth wire, if present, is provided as a neutral and is normally grounded. The three-wire and four-wire designations do not count the ground wire present above many transmission lines, which is solely for fault protection and does not carry current under normal use. A four-wire system with symmetrical voltages between phase and neutral is obtained when

1136-455: Is 3 = 1.732 … {\displaystyle {\sqrt {3}}=1.732\ldots } times the amplitude of the voltage of the individual phases. The symmetric three-phase systems described here are simply referred to as three-phase systems because, although it is possible to design and implement asymmetric three-phase power systems (i.e., with unequal voltages or phase shifts), they are not used in practice because they lack

1207-417: Is √ 3 times greater than the line-to-neutral voltage delivered to a load in the wye configuration. As the power transferred is V / Z , the impedance in the delta configuration must be 3 times what it would be in a wye configuration for the same power to be transferred. Except in a high-leg delta system and a corner-grounded delta system, single-phase loads may be connected across any two phases, or

1278-421: Is a type of polyphase system employing three wires (or four including an optional neutral return wire) and is the most common method used by electrical grids worldwide to transfer power. Three-phase electrical power was developed in the 1880s by several people. In three-phase power, the voltage on each wire is 120 degrees phase shifted relative to each of the other wires. Because it is an AC system, it allows

1349-441: Is called phase voltage . For example, for a 208/120-volt service, the line voltage is 208 volts, and the phase voltage is 120 volts. Polyphase power systems were independently invented by Galileo Ferraris , Mikhail Dolivo-Dobrovolsky , Jonas Wenström , John Hopkinson , William Stanley Jr. , and Nikola Tesla in the late 1880s. Three phase power evolved out of electric motor development. In 1885, Galileo Ferraris

1420-422: Is created or opened in the page cache, but not written to, might result in a zero byte file at a later read. However, not all cached pages can be written to as program code is often mapped as read-only or copy-on-write ; in the latter case, modifications to code will only be visible to the process itself and will not be written to disk. In 2019, security researchers demonstrated side-channel attacks against

1491-406: Is mainly used directly to power large induction motors , other electric motors and other heavy loads. Small loads often use only a two-wire single-phase circuit, which may be derived from a three-phase system. The conductors between a voltage source and a load are called lines, and the voltage between any two lines is called line voltage . The voltage measured between any line and neutral

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1562-410: Is not necessarily 0 and depends on the type of load impedance, Z y . Inductive and capacitive loads will cause current to either lag or lead the voltage. However, the relative phase angle between each pair of lines (1 to 2, 2 to 3, and 3 to 1) will still be −120°. By applying Kirchhoff's current law (KCL) to the neutral node, the three phase currents sum to the total current in the neutral line. In

1633-658: Is often preferred over flushing the dirty pages into secondary storage and reusing their space. Executable binaries , such as applications and libraries, are also typically accessed through page cache and mapped to individual process spaces using virtual memory (this is done through the mmap system call on Unix-like operating systems). This not only means that the binary files are shared between separate processes, but also that unused parts of binaries will be flushed out of main memory eventually, leading to memory conservation. Since cached pages can be easily evicted and re-used, some operating systems, notably Windows NT , even report

1704-441: Is possible with any number of phases greater than one. However, two-phase systems do not have neutral-current cancellation and thus use conductors less efficiently, and more than three phases complicates infrastructure unnecessarily. Additionally, in some practical generators and motors, two phases can result in a less smooth (pulsating) torque. Three-phase systems may have a fourth wire, common in low-voltage distribution. This

1775-403: Is the neutral wire. The neutral allows three separate single-phase supplies to be provided at a constant voltage and is commonly used for supplying multiple single-phase loads. The connections are arranged so that, as far as possible in each group, equal power is drawn from each phase. Further up the distribution system , the currents are usually well balanced. Transformers may be wired to have

1846-404: Is the phase of delta impedance ( Z Δ ). Inspection of a phasor diagram, or conversion from phasor notation to complex notation, illuminates how the difference between two line-to-neutral voltages yields a line-to-line voltage that is greater by a factor of √ 3 . As a delta configuration connects a load across phases of a transformer, it delivers the line-to-line voltage difference, which

1917-406: Is used by the operating system for the page cache. Since the memory would otherwise be idle and is easily reclaimed when applications request it, there is generally no associated performance penalty and the operating system might even report such memory as "free" or "available". When compared to main memory, hard disk drive read/writes are slow and random accesses require expensive disk seeks ; as

1988-689: The System/370 's processor instructions, so that it could run a slightly modified version of IBM's APL mainframe program interpreter. In 1980 rumors spread of a new IBM personal computer, perhaps a miniaturized version of the 370. In 1981 the IBM Personal Computer appeared, but it was not based on the System 370 architecture. However, IBM did use their new PC platform to create combinations with additional hardware that could execute S/370 instructions locally. In October 1983, IBM announced

2059-582: The UK may supply one phase and neutral at a high current (up to 100  A ) to one property, while others such as Germany may supply 3 phases and neutral to each customer, but at a lower fuse rating, typically 40–63 A per phase, and "rotated" to avoid the effect that more load tends to be put on the first phase. Based on wye (Y) and delta (Δ) connection. Generally, there are four different types of three-phase transformer winding connections for transmission and distribution purposes: In North America,

2130-508: The "neutral" and either of the center-tapped phase points. In the perfectly balanced case all three lines share equivalent loads. Examining the circuits, we can derive relationships between line voltage and current, and load voltage and current for wye- and delta-connected loads. In a balanced system each line will produce equal voltage magnitudes at phase angles equally spaced from each other. With V 1 as our reference and V 3 lagging V 2 lagging V 1 , using angle notation , and V LN

2201-688: The IBM Personal Computer XT/370. This was essentially a three-in-one product. It could run PC DOS locally, it could also act as 3270 terminal, and finally—its most important distinguishing feature relative to an IBM 3270 PC —was that it could execute S/370 instructions locally. The XT/370 was an IBM Personal Computer XT (System Unit 5160) with three custom 8-bit cards. The processor card (370PC-P), contained two modified Motorola 68000 chips (which could emulate most S/370 fixed-point instructions and non-floating-point instructions), and an Intel 8087 coprocessor modified to emulate

PC-based IBM mainframe-compatible systems - Misplaced Pages Continue

2272-587: The PC Server 520 added two PCI expansion slots and removed two MCA slots. The S/390 Integrated Server (aka S/390 IS) is a mainframe housed in a comparably small case (HxWxD are 82 x 52 x 111 cm). It became available from November 1998. It is intended for customers who do not require the I/O bandwidth and performance of the S/390 Multiprise 3000 (which has the same size). Only 256 MB of ECC Memory and

2343-565: The PC version these were maintained as PC DOS files, either on floppy or hard disk. For example, the CMS virtual disk belonging to user FRED at device address 101 was stored as the DOS file FRED.101. The CMS IMPORT and EXPORT commands allowed extraction of files from these virtual drives as well as ASCII / EBCDIC conversion. The XT/370 came with an XT-style 83-key keyboard (10 function keys). Newer revisions of

2414-645: The Personal/370 (aka P/370), a single slot 32-bit MCA card that can be added to a PS/2 or RS/6000 computer to run System/370 OSs (like MUSIC/SP , VM , VSE ) parallel to OS/2 (in PS/2) or AIX (in RS/6000) supporting multiple concurrent users. It is a complete implementation of the S/370 Processor including a FPU co-processor and 16 MB memory. Management and standard I/O channels are provided via

2485-467: The R/390. The original P/390 server was housed in an IBM PC Server 500 and featured a 90 MHz Intel Pentium processor for running OS/2. The model was revised in mid-1996 and rebranded as the PC Server 520, which featured a 133 MHz Intel Pentium processor. Both models came standard with 32 MB of RAM and were expandable to 256 MB. The PC Server 500 featured eight MCA expansion slots while

2556-518: The RAM on the 370PC-M card. Besides the 416  kB of usable RAM for S/370 applications, the XT/370 also supported up to 4  MB of virtual memory using the hard drive as its paging device. IBM claimed the XT/370 reached 0.1 MIPS (when the data fit in RAM). In 1984, the list price of an XT/370 in its typical configuration was approximately $ 12,000 so compared favorably with IBM's own mainframes on

2627-511: The S/370 floating point instructions. The second card (370PC-M), which connected to the first with a unique card back connector contained 512 KiB of memory. The third card (PC3277-EM), was a 3270 terminal emulator required to download system software from the host mainframe. The XT/370 computer booted into DOS, then ran the VM /PC Control Program. The card's memory space added additional system memory, so

2698-519: The XT/370 dropped the PC3277-EM in favor of the IBM 3278/79 boards. The XT/370 was among the XT systems that could use a second hard drive mounted in the 5161 expansion chassis. BYTE in 1984 called the XT/370 "a qualified success". The magazine praised IBM for "fitting all of the 370's features into the XT", and hoped for technical improvements that "might result in an even better computer". The XT/370

2769-531: The balanced case: In the delta circuit, loads are connected across the lines, and so loads see line-to-line voltages: (Φ v1 is the phase shift for the first voltage, commonly taken to be 0°; in this case, Φ v2 = −120° and Φ v3 = −240° or 120°.) Further: where θ is the phase of delta impedance ( Z Δ ). Relative angles are preserved, so I 31 lags I 23 lags I 12 by 120°. Calculating line currents by using KCL at each delta node gives and similarly for each other line: where, again, θ

2840-425: The cached page for the particular block is looked up. If it is already found in the page cache, the write is done to that page in the main memory. If it is not found in the page cache, then, when the write perfectly falls on page size boundaries, the page is not even read from disk, but allocated and immediately marked dirty. Otherwise, the page(s) are fetched from disk and requested modifications are done. A file that

2911-466: The configuration. The MCA P/390 expansion card can be installed in any MCA RS/6000 system, while the PCI P/390 card can be installed in a number of early PCI RS/6000s; all such configurations are referred to as an R/390. R/390 servers need to run AIX version 4 as the host operating system. P/390 was the designation used for the expansion card used in an IBM PC Server and was less expensive than

PC-based IBM mainframe-compatible systems - Misplaced Pages Continue

2982-399: The country. At the power station, transformers change the voltage from generators to a level suitable for transmission in order to minimize losses. After further voltage conversions in the transmission network, the voltage is finally transformed to the standard utilization before power is supplied to customers. Most automotive alternators generate three-phase AC and rectify it to DC with

3053-598: The design of the S/390 Processor Card was complete compatibility with existing mainframe operating systems and software. The processor implements all of the ESA/390 and XA instructions which prevents the need for instruction translation. There are three generations of the card: R/390 was the designation used for the expansion card used in an IBM RS/6000 server. The original R/390 featured a 67 or 77 MHz POWER2 processor and 32 to 512 MB of RAM, depending on

3124-461: The distribution network so the loads are balanced as much as possible, since the same principles that apply to individual premises also apply to the wide-scale distribution system power. Hence, every effort is made by supply authorities to distribute the power drawn on each of the three phases over a large number of premises so that, on average, as nearly as possible a balanced load is seen at the point of supply. For domestic use, some countries such as

3195-530: The first 256  KiB ( motherboard ) memory could be used to move data to the 512 KiB expansion card. The expansion memory was dual ported, and provided an additional 384 KiB to the XT Machine bringing the total RAM on the XT side to 640 KiB . The memory arbitrator could bank switch the second 128 KiB bank on the card to other banks, allowing the XT Intel 8088 processor to address all

3266-553: The growth of power-transmission network grids on continents around the globe. Mikhail Dolivo-Dobrovolsky developed a three-phase electrical generator and a three-phase electric motor in 1888 and studied star and delta connections . His three-phase three-wire transmission system was displayed in 1891 in Germany at the International Electrotechnical Exhibition , where Dolivo-Dobrovolsky used

3337-489: The high end of its BS2000 line. Since the late 1990s, PC processors have become fast enough to perform mainframe emulation without the need for a coprocessor card. There are currently several personal computer emulators available that support System/390 and z/Architecture . Three-phase electric power Three-phase electric power (abbreviated 3ϕ ) is a common type of alternating current (AC) used in electricity generation , transmission , and distribution . It

3408-471: The host OS/hardware. An additional 370 channel card can be added to provide mainframe-specific I/O such as 3270 local control units, 3400/3480 tape drives or 7171 protocol converters. Although a single-card product, the P/370 ran three times faster than the 7437, attaining 3.5 MIPS, on par with a low-end IBM 4381 . A subsequent book (by the same author) claims 4.1 MIPS for the P/370. The Personal/370

3479-528: The identity of phases is required if two sources could be connected at the same time. A direct connection between two different phases is a short circuit and leads to flow of unbalanced current. As compared to a single-phase AC power supply that uses two current-carrying conductors (phase and neutral ), a three-phase supply with no neutral and the same phase-to-ground voltage and current capacity per phase can transmit three times as much power by using just 1.5 times as many wires (i.e., three instead of two). Thus,

3550-529: The lower end of Fujitsu's S/390-based BS2000 mainframe product line. The SQ100 is the slower configuration, using dual-core 2.93   GHz Intel Xeon E7220 processors, and is capable of up to 200RPF of performance. The SQ200 was introduced more recently, uses six-core 2.66   GHz Xeon X7542 processors, and has performance of up to 700RPF. All Intel 64 -based BS2000 mainframes can run Linux or Windows in separate partitions. Fujitsu also continues to make custom S/390-native processors and mainframe hardware for

3621-441: The most important advantages of symmetric systems. In a three-phase system feeding a balanced and linear load, the sum of the instantaneous currents of the three conductors is zero. In other words, the current in each conductor is equal in magnitude to the sum of the currents in the other two, but with the opposite sign. The return path for the current in any phase conductor is the other two phase conductors. Constant power transfer

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3692-426: The neutral (which is common to the three phases). When a group of customers sharing the neutral draw unequal phase currents, the common neutral wire carries the currents resulting from these imbalances. Electrical engineers try to design the three-phase power system for any one location so that the power drawn from each of three phases is the same, as far as possible at that site. Electrical engineers also try to arrange

3763-550: The neutral is connected to the "common star point" of all supply windings. In such a system, all three phases will have the same magnitude of voltage relative to the neutral. Other non-symmetrical systems have been used. The four-wire wye system is used when a mixture of single-phase and three-phase loads are to be served, such as mixed lighting and motor loads. An example of application is local distribution in Europe (and elsewhere), where each customer may be only fed from one phase and

3834-419: The other conductors and one third of a cycle before the remaining conductor. This phase delay gives constant power transfer to a balanced linear load. It also makes it possible to produce a rotating magnetic field in an electric motor and generate other phase arrangements using transformers (for instance, a two-phase system using a Scott-T transformer ). The amplitude of the voltage difference between two phases

3905-462: The page cache usage as "available" memory, while the memory is actually allocated to disk pages. This has led to some confusion about the utilization of page cache in Windows. The page cache also aids in writing to a disk. Pages in the main memory that have been modified during writing data to disk are marked as "dirty" and have to be flushed to disk before they can be freed. When a file write occurs,

3976-438: The page cache. The operating system may also use some of main memory as filesystem write buffer, it may be called page buffer . Pages in the page cache modified after being brought in are called dirty pages. Since non-dirty pages in the page cache have identical copies in secondary storage (e.g. hard disk drive or solid-state drive), discarding and reusing their space is much quicker than paging out application memory, and

4047-401: The phase and anti-phase lines is 240 V (200%), and the neutral to "high leg" voltage is ≈ 208 V (173%). The reason for providing the delta connected supply is usually to power large motors requiring a rotating field. However, the premises concerned will also require the "normal" North American 120 V supplies, two of which are derived (180 degrees "out of phase") between

4118-531: The polyphase alternator is key in the history of electrification, as is the power transformer. These inventions enabled power to be transmitted by wires economically over considerable distances. Polyphase power enabled the use of water-power (via hydroelectric generating plants in large dams) in remote places, thereby allowing the mechanical energy of the falling water to be converted to electricity, which then could be fed to an electric motor at any location where mechanical work needed to be done. This versatility sparked

4189-433: The power grid and use a split-phase system to the panelboard from which most branch circuits will carry 120 V. Circuits designed for higher powered devices such as stoves, dryers, or outlets for electric vehicles carry 240 V. In Europe, three-phase power is normally delivered to the panelboard and further to higher powered devices. At the power station , an electrical generator converts mechanical power into

4260-566: The ratio of capacity to conductor material is doubled. The ratio of capacity to conductor material increases to 3:1 with an ungrounded three-phase and center-grounded single-phase system (or 2.25:1 if both use grounds with the same gauge as the conductors). That leads to higher efficiency, lower weight, and cleaner waveforms. Three-phase supplies have properties that make them desirable in electric power distribution systems: However, most loads are single-phase. In North America, single-family houses and individual apartments are supplied one phase from

4331-399: The same frequency and voltage amplitude relative to a common reference, but with a phase difference of one third of a cycle (i.e., 120 degrees out of phase) between each. The common reference is usually connected to ground and often to a current-carrying conductor called the neutral. Due to the phase difference, the voltage on any conductor reaches its peak at one third of a cycle after one of

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4402-440: The system to transmit electric power at the distance of 176 km (110 miles) with 75% efficiency . In 1891 he also created a three-phase transformer and short-circuited ( squirrel-cage ) induction motor . He designed the world's first three-phase hydroelectric power plant in 1891. Inventor Jonas Wenström received in 1890 a Swedish patent on the same three-phase system. The possibility of transferring electrical power from

4473-527: The terminal emulation function, the AT/370 came with the same 3278/79 Emulation Adapter as the late-series XT/370. The AT/370 motherboard itself was equipped with 512 KB of RAM. The AT/370 also ran VM/PC, but with PC DOS 3.0 instead of 2.10 that the XT version used. VM/PC version 2, launched in November 1985, improved performance by up to 50%; it allowed add-on memory (in addition to the disk) to be used as

4544-456: The transformers has failed or needs to be removed. In open delta, each transformer must carry current for its respective phases as well as current for the third phase, therefore capacity is reduced to 87%. With one of three transformers missing and the remaining two at 87% efficiency, the capacity is 58% ( 2 ⁄ 3 of 87%). Where a delta-fed system must be grounded for detection of stray current to ground or protection from surge voltages,

4615-501: The voltage between the line and the neutral we have: These voltages feed into either a wye- or delta-connected load. The voltage seen by the load will depend on the load connection; for the wye case, connecting each load to a phase (line-to-neutral) voltages gives where Z total is the sum of line and load impedances ( Z total = Z LN + Z Y ), and θ is the phase of the total impedance ( Z total ). The phase angle difference between voltage and current of each phase

4686-403: The voltages to be easily stepped up using transformers to high voltage for transmission and back down for distribution, giving high efficiency. A three-wire three-phase circuit is usually more economical than an equivalent two-wire single-phase circuit at the same line-to-ground voltage because it uses less conductor material to transmit a given amount of electrical power. Three-phase power

4757-496: Was $ 18,100 for a minimum 25-unit order. One of its intended roles was to provide a single-user S/370-compatible computer that could run computer-aided design and engineering applications that originated on IBM mainframes such as CADAM and CATIA . Graphics support was provided by an IBM 5080 graphics system, a floor-standing tower. The 5080 was connected to the 7437 through the PS/2 via a cable and MCA adapter. Later, IBM introduced

4828-483: Was a freestanding tower that connected to a MCA card installed in a PS/2 Model 60 , 70, or 80. The 7437 tower contained the processor and a 16   Mbytes main memory, and the PS/2 provided I/O and disk storage. The 7437 ran the IBM VM/SP operating system, and one IBM representative described the 7437 "like a 9370 with a single terminal". It was intended for existing S/370 users and its November 1988 list price

4899-476: Was available as early as November 1989 although on a "special bid basis". In 1995 IBM introduced a card, the "Enhanced S/390 MicroProcessor Complex", which supported IBM ESA/390 architecture on a PC-based system. IBM's PC-related products evolved to support that as well, employing the card (IBM part number 8640-PB0) in the "IBM PC Server 330 in 1998 and the IBM PC Server 500 models. An important goal in

4970-738: Was discontinued in April 1987. In 1984, IBM introduced the IBM Personal Computer AT/370 with similar cards as for the XT/370 and updated software, supporting both larger hard disks and DMA transfers from the 3277 card to the AT/370 Processor card. The system was almost 60% faster than the XT/370. The AT/370 used different, 16-bit interface co-processing cards than the XT, called PC/370-P2 and PC/370-M2. The latter card still had only 512 KB for memory, out of which 480 KB were usable for programs in S/370 mode, while 32 KB were reserved for microcode storage. For

5041-426: Was doing research on rotating magnetic fields . Ferraris experimented with different types of asynchronous electric motors . The research and his studies resulted in the development of an alternator , which may be thought of as an alternating-current motor operating in reverse, so as to convert mechanical (rotating) power into electric power (as alternating current). On 11 March 1888, Ferraris published his research in

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