By default, the guest synchronizes its time with the hypervisor as follows: When the guest system boots, the guest reads the time from the emulated Real Time Clock (RTC).When the NTP protocol is initiated, it automatically synchronizes the guest clock. Afterwards, during normal guest operation, NTP performs clock adjustments in the guest.When a guest is resumed after a pause or a restoration process, a command to synchronize the guest clock to a specified value should be issued by the management software (such as virt-manager). This synchronization works only if the QEMU guest agent is installed in the guest and supports the feature. The value to which the guest clock synchronizes is usually the host clock value.
QEMU can simulate several network cards (e.g. PCI or ISA cards on the PCtarget) and can connect them to a network backend on the host or anemulated hub. The various host network backends can either be used toconnect the NIC of the guest to a real network (e.g. by using a TAPdevices or the non-privileged user mode network stack), or to otherguest instances running in another QEMU process (e.g. by using thesocket host network backend).
Usb Emul Win32 Setup.epubl
QEMU can simulate several hubs. A hub can be thought of as a virtualconnection between several network devices. These devices can be forexample QEMU virtual ethernet cards or virtual Host ethernet devices(TAP devices). You can connect guest NICs or host network backends tosuch a hub using the -netdevhubport or -nic hubport options. The legacy -net option alsoconnects the given device to the emulated hub with ID 0 (i.e. thedefault hub) unless you specify a netdev with -net nic,netdev=xxxhere.
Using the -netdev socket (or -nic socket or -net socket)option, it is possible to create emulated networks that span severalQEMU instances. See the description of the -netdev socket option inInvocation to have a basicexample.
List of the most common filename extensions used when a game's ROM image or storage medium is copied from an original read-only memory (ROM) device to an external memory such as hard disk for back up purposes or for making the game playable with an emulator. In the case of cartridge-based software, if the platform specific extension is not used then filename extensions ".rom" or ".bin" are usually used to clarify that the file contains a copy of a content of a ROM. ROM, disk or tape images usually do not consist of one file or ROM, rather an entire file or ROM structure contained within one file on the backup medium.[34]
Emulators are slightly different. They allow you to run an operating system that requires (say)an Intel/AMD x86 processor on a completely different CPU (processor). For example, it may allow you to run Windows XP ona PowerPC processor (something that normally won't work, since Windows XP requires an x86 processor). In other words,unlike the VM which only has to virtualize some of the hardware, emulators have to emulate everything, including theCPU. As such, emulators tend to be much slower than VMs.
This page lists both VMs and emulators for the Intel/AMD x86 (32 or 64 bits) processors (meaning that they eitheremulate the x86 or are virtual machines that run on the x86). The guest "machines" they create may or may not(depending on which software you choose) be able to provide access to your real computer's USB drives, CD/DVD drives,printers, network, etc.
Some additional useful terminology that you may find useful: in the world of emulators and virtualmachines, the host refers to your real, physical computer that you're currently using to read thispage. For example, if you're using a computer running Mac OS X, then that computer is your host computer, Mac OS X isyour host operating system, and so on. If you run a virtual machine on that computer, and install (say)Windows 7 into thatvirtual machine, then that Windows 7 is the guest operating system.
QEMU supports the emulation of x86 processors, ARM, SPARC and PowerPC. Host CPUs (processors that can run the QEMUemulator) include x86, PowerPC, Alpha, Sparc32, ARM, S390, Sparc64, ia64, and m68k (some of these are still indevelopment). When emulating a PC (x86), supported guest operating systems include MSDOS, FreeDOS, Windows 3.11,Windows 98SE, Windows 2000, Linux, SkyOS, ReactOS, NetBSD, Minix, etc. When emulating a PowerPC, currently tested guest OSesinclude Debian Linux.
Xen is an open source virtual machine that allows you to run multiple guest operating systems partitioned in their ownvirtual machines. It currently runs on Linux (as the host operating system). Supported guest operating systems includeLinux, Windows XP (work in progress), NetBSD and FreeBSD. Unlike some of the other virtual machines and emulators, however,Xen requires you to have a modified version of the operating system as the guest OS.
Bochs is an open source emulator for IA-32 (Intel x86) machines. It has the ability to emulate a 386, 486, Pentium,Pentium Pro, AMD64, with or without MMX, SSE, SSE2 and 3DNow, with common I/O devices (such as a SoundBlaster sound card,a NE2000 compatible network card, etc) and a custom BIOS.You can run Windows 95/NT, Linux and DOS as guest operating systems in that machine. Your guest OS will be installed in alarge file which the emulator will use to mimic a hard disk for the emulated machine. Supported platforms (and hereI mean platforms on which Bochs will run) include Win32 (Windows 9x/ME/2k/XP), Macintosh, Mac OS X, BeOS, Amiga MorphOS,OS/2, and Unix/X11 systems (including Linux).
JPC is a PC emulator written using the Java programming language,and thus runs on any computer that has theJava runtime environment installed (eg Windows, Linux,Mac OS X, etc). At the time this mini-review was written, the emulator is able to run all versions ofDOS as well as some versionsof Linuxand OpenBSD. Note: if you need to run seriousprograms (other than DOS games), you should probably choose one of the other emulators onthis page. The emulator is probably intended more for academic interestand amusement than serious emulation tasks. (It is after all an emulator running on a virtual machine.)
DOSBox is an x86 emulator with a built-in DOS. It was created primarily to run DOS games. It emulates a 286/386 inreal and protected modes, XMS/EMS, a graphics card (VGA/EGA/CGA/VESA/Hercules/Tandy), SoundBlaster/Gravis Ultra sound card,etc. You can apparently even run the old 16-bit Windows 3.1 in the emulator. Host operating systems (ie, platforms onwhich you can run the DOSBox emulator) include Windows, Linux, Mac OS X, BeOS, FreeBSD, MorphOS and Amiga68k.
WINE, which stands for WINE Is Not an Emulator, allows you to run Windows programs in Linux and other Unix-type systems.It is a layer that emulates the Windows API on Unix systems running X. You do not need to have Windows at all to run yourWindows applications in WINE. If you are looking for Windows emulators or clones, you may also want to check out theFree Windows Clones, Emulators and Emulation Layerspage.
[Update: the Q website seems to have disappeared.]Q is a port of QEMU (see elsewhere on this page) thatallows you to run Windows, Linux, etc, on your Mac. You can exchange files between your host and guest operating systems.Q runs on Mac OS X running on either an Intel processor or the older PowerPC G4/G5 processor. Depending on whether yourun it on OS X Lion or earlier, it can emulate a PC (x86 or x86_64 processor), a PowerPC (PPC), a G3,a Sun4m (32 bit Sparc processor), Sun4u (64 bit Sparc processor), Malta (32 bit MIPS processor) and a Mac99 PowerMac.(The Sparc, MIPS and possibly x86_64 guests are not available on Lion, at the time I write this.)It emulates a Soundblaster 16 card, a Cirrus CLGD 5446 PCI VGA card (or a dummy VGA card with Bochs VESA extensions),a PS/2 mouse and keyboard, 2 PCI IDE interfaces with hard diskand CD-ROM support, a floppy disk, NE2000 PCI network adapters and serial ports. 2ff7e9595c
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