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[ros-kernel] RE: Re: RE: Thoughts about loadros
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From: Brian P. <br...@sg...> - 2001-11-12 20:29:02
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While switching to and from protected/real modes to make BIOS calls is certainly slower, I don't think I would trade it for flat real mode. What if inside one of the BIOS calls it decides to reload a selector for you? This would most likely not be a problem for the most basic disk i/o stuff but the system memory map calls and extended disk i/o I would beware. Besides, short of writing my own protected mode disk driver for FreeLoader there is no other alternative than switching back to real mode and calling the BIOS. Plus you would have to use low memory buffers for your disk reads in flat real mode also, the BIOS doesn't accept 32-bit buffer addresses unless you are using LBA calls. Brian -----Original Message----- From: Eric Kohl [mailto:ek...@rz...] Sent: Monday, November 12, 2001 3:21 AM To: ros...@re... Subject: [ros-kernel] Re: RE: Thoughts about loadros "Brian Palmer" <br...@sg...> wrote: > As of version 11.0c, Watcom C/C++ is going to be open source. > www.openwatcom.org AFAICS it is only an update yet. The full version is not available. And it is huuuuge, the update is more than 45MB. :-/ > Although it would be useful for loadros to support the registry, and being > able to boot from DOS is handy, I don't think that turning it into a full > boot loader would be worthwhile. There is too much that would need to be > added that is already there in FreeLoader. To me loadros has always seemed > like a hack that needs to be put out to pasture. You're right, the existing loadros is a hack. But OTOH, FreeLoader is not that much better. For each bios call FreeLoader must switch to real mode and back to protected mode while a modified loadros runs in flat real mode, this means it can call into the bios without mode switching and can access the full 4GB physical memory space. AFAIR, the main problem with FreeLoader was the 32bit disk access. IMHO it is extremely bad to call these bios functions from protected mode. It is not only the mode-switching but especially the fact that all parameters have to be passed to the bios in a buffer. Brrr.. :-/ - Eric Kohl ==================================================== = To remove yourself from this mailing list, go to = = http://www.reactos.com/home/mailing.html = ==================================================== ==================================================== = To remove yourself from this mailing list, go to = = http://www.reactos.com/home/mailing.html = ==================================================== |
