[ Pobierz całość w formacie PDF ]
.Not all disksare as fast under DOSemu, with performance degradation ranging from small to huge.As with CPU speed, disk speed depends on what other Linux tasks are doing.Video PerformanceVideo support is Linux's Achilles' heel.Text performance is much slower when not running DOSemu under a virtual console.Under a virtual console, benchmarked text speed approaches that of native MS-DOS.When you are using real-world applications, thetext speed is dramatically slower, with an observed speed as low as 20 percent of the speed under native MS-DOS.Graphics speed is even worse.Mouse SupportFor mouse support, you can get Microsoft compatible mouse drivers from oak.oakland.edu:/Simtel/msdos/mouse/mouse701.zip (mscmouse).Make sure you have the correct port assigned to the mouse.Even so, some mice do not get recognized for up to 60 seconds,so be patient.Another known problem is that DOSemu is not able to use COM4 after DOSemu finishes execution.This port is at 0x2E8, /dev/cua3 in Linux and uses interrupt 5.You can run the command:setserial /dev/cua3 irq 5Another cure is to disable the allowvideoportaccess on line in the config file.Optimizing DOSemuThere are a few changes that will help DOS performance under DOSemu short of buying a faster PC.Using GarrotGarrot is an MS-DOS based Terminate and Stay Resident (TSR) program written by Thomas G.McWilliams that releases CPU time from a DOSemu process back to Linux.Some MS-DOS applications poll endlessly on events such as keyboard input.Garrot keeps trackof how long a DOS application has been running without giving control back to Linux.After a threshold of time has expired, control returns to Linux.The Garrot threshold is best determined by trial and error.A good initial value is half the bogo-mipsvalue.Bogo-mips is the value that the Linux kernel assigns for internal delay loops, and is displayed when booting the Linux kernel.For CPU-intensive DOS applications, Garrot will cause a minor degradation in CPU speed.For non-CPU—intensive applications, Garrot will show a dramatic decrease in overall CPU usage, as measured by the Linux utility top.Other Optimization SuggestionsThe following parameters in dosemu.conf will help speed up various aspects of DOSemu:Hogthreshold.Set this to half the value shown in boot up messages for BogoMIP message.fastfloppyX parameters "updatefreq" and "updatelines"-c option on the DOS command lineBecause DOSemu runs as a Linux process, any general Linux optimizations should also help performance under DOSemu.Typical optimizations include having enough swap space, optimizing the kernel, and killing unneeded Linux processes.Sources for More Documentation About DOSemuThe DOSemu manual (dosemu.texinfo) written by Robert Sanders has not been updated in some time but is still a good source of information.It is distributed with DOSemu.The "dosEMU Novice's Altering Guide" or DANG is a road map to the inner workings of DOSemu.It is designed for the adventurous, those people who wish to modify the source code themselves.DANG is maintained by Alistair MacDonald(am20@unix.york.ac.uk) and is posted periodically to the MSDOS channel of Linux Activists.The EMU success list (EMUsuccess.txt) is a list of all programs that have been reported to work with DOSemu.It is posted periodically to the mailing list.The most recent version can be found on dspsun.eas.asu.edu/pub/dosemu.Of course, there is the DOSemu FAQ/HOWTO.But you already know about that, don't you? It is also posted frequently to the mailing list.The most recent version can be found on dspsun.eas.asu.edu/pub/dosemu.Where To Get More Information About DOSemuTry subscribing to the linux-msdos-digest mailing list.To subscribe, send e-mail to Majordomo@vger.rutgers.edu with the following command in the body of your e-mail message:subscribe linux-msdos-digest your_username@your.email.addressTo get rid of these messages, send e-mail to Majordomo@vger.rutgers.edu with the following command in the body of your e-mail message:unsubscribe linux-msdos-digest your_username@your.email.addressThe Netware-HOWTO by Lauri Tischler (ltischler@fipower.pp.fi) is now a separate document.It is included with the DOSemu distribution and may also be found at sunsite.unc.edu.How DOSemu WorksDOSemu works similar to the DOS feature of MS Windows in that it uses the virtual 86 (vm86) feature of the i386 and above chips.Under vm86, a process runs under a private 80x86 environment that is isolated by the i386 processor from any other process.In addition to private access to an 80´86 processor, MS-DOS and MS-DOS applications need to interact with PC hardware through port accesses and interrupt functions.In vm86 mode, both port access and interrupts return vm86 back to the DOSemu.For port access attempts, DOSemu tries to recognize the port, and either simulates its function or passes the request to the real hardware.Ports that DOSemu are allowed to map are configured by the Port parameter in dosemu.conf.Direct access tohardware ports is possible under Linux through /dev/kmem support.DOS interrupt functions are widely understood and well-documented.Interrupts are caught from virtual 86 mode, and are implemented by executing the equivalent functionality as Linux system calls.A Brief History of DOSemu and Its Contributing AuthorsThe first release of DOSemu was written by Matthias Lautner in September 1992.Since that time, many other people have contributed major pieces of functionality.There are too many authors to name, but some of the more significant contributors includeRobert Sanders, James MacLean, Andres Tridgell, Stephen Tweedie, and Andreas Kies.Other parts of DOSemu functionality were borrowed from Carnegie Mellon's MACH DOS emulator
[ Pobierz całość w formacie PDF ]