From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ronald G Minnich To: <9fans@cse.psu.edu> Subject: Re: [9fans] non-BIOS boot In-Reply-To: <8f6cf824.0205291150.157c7698@posting.google.com> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Date: Thu, 30 May 2002 09:15:36 -0600 Topicbox-Message-UUID: a0055ed8-eaca-11e9-9e20-41e7f4b1d025 On Thu, 30 May 2002, Don wrote: > If you dont use the BIOS wouldn't you have to access > the disk via i/o ports? If so, you would have to adhere to > the SCSI/ATA standard rather than a more conformed interface > via int13? Great question. I used to think this too. Turns out PC hardware is designed for two things: full-capability OSes and really STUPID STUPID BIOSes. So, for example, IDE hardware runs with all kinds of fancy DMA, and also runs in trivial polled-IO modes so that software written ca. 1982 will work correctly. It's really amazing to see the contortions PC hardware goes through to conform to an Intel reference design from 1978 or so (not kidding, I have some of those old books somewhere). It turns out that the INT13 is no more conforming than the silly hardware. What we do in LinuxBIOS for IDE support is run dead-stupid simple polled-IO drivers to load the kernel. These were contributed by someone from another project. > If you did have to adhere to the different standards > wouldnt that mean implementing the drivers in the MBR/PBS? Yes, you are right here, but this has turned out to be not a big deal (so far). ron