I received this from Eric in PVT. I am copying it here because I just agree with almost all of it!!
I will just add atha almost all big DOS programs that are performance aware do most disk access in big chunks buffering it in memory (even write cache is available in CodeBase). This make them even less sensitive to using DOS in 16 bit. Alain > be gained is just not having to switch to 16 bit mode and back every time a > dos function is called. This switch is what takes a lot of time, in view of The "a lot of" depends on which CPU generation you use. On Pentium class systems, you can often get a faster switching mode. Our EMM386 does not yet make use of that. And the DOS kernel is not called as often as you may think. The worst case would be writing CON or even a disk file with one call for each byte, but most software is not that "silly"... Disk access is a good example for how inefficient DOS actually is: Each access has to flow through at least half a dozen layers before it reaches the disk, and CON access has similar amounts of overhead. But you have to implement all layers to be compatible. I wonder how many layers are implemented in DOSBox - Apps can probably live with a minimal simulation, it is the drivers which need all that extra complexity under the hood to be compatible. For example network- and cdrom drives need it. > - Modern OSs like Linux are not only much faster, > but have many more tricks in their bags, like cacheing etc.. Of course you can cache in DOS, too... But in Linux, the cache shares memory with the rest of the system, and there are high end algorithms working on large and/or advanced data structures. To have that stuff in DOS, you would have to let your drivers work in protected mode, which will cause some extra overhead... Yet it is possible that a protected mode version of the disk cache driver could give DOS some extra punch. > - Bios would be useless, so drivers would have to be from scratch. Depends. You can have wrappers... Basically you will have to do with the BIOS what you did with DOS before: Call it in a non- protected mode context :-). Of course this still has the usual overhead then. Replacing some BIOS calls with calls to direct hardware drivers would help with speed but would make compatib- ility with nonstandard hardware worse. Eric ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 _______________________________________________ Freedos-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freedos-devel
