winscape 2240

More like a score of systems (the MS windows stuff is also different from release to release). So we got W98, W2k, Wxp, WNT, Wme and WinCe, FreeBSD, NetBSD, OpenBSD, Dragonfly, Linux, Linux, Linux Solaris, QNX and Minix all having different bootsequences and drivers, and need to talk to generalized hardware.

Microsoft rightly complains about the quality of the third party drivers supplied with new hardware products. The ones (about half of them) that supply "ready-made" linux drivers almost never see them included into the standard linux code base without substantial changes. The quality isn't up to it. The drivers are more like "proof of operation" drivers rather than production code.

Linux now has more than 10k drivers for different hardware. It is a priority to bring this number down. It is not better in the windows world.

The solution is to simplify things on the hardware side, and make hardware that can use already existing drivers. USB has been a huge driver for this. USB is fast and flexible enough to use even for disk drives.

It would be a good project to describe the then PC architecture, and ask what a good solution would be. I guess it would have looked more like Xenix, QNX, Minix or MP-M than MSDOS:

The PC goes there automagically; but can be halted during the little timing window when the BIOS code is executing.

I guess you need an update of what has happened since you left CPU development. Disks are now truly digital devices, not half way analog as they were up to around 1990 with the ST506, SMD, ESMD etc interfaces. The main CPU no longer controls head movement. The disk does that on it's own; list like an intelligent waiter it is taking orders and comes back with the results.

Now almost all disks run some form of SCSI command set. The physical layer can be ATA (as in el-cheapo disks), physical SCSI, USB, SATA, Firewire, or even ethernet. But it is all a comms channel.

So both sides need to bring the channel up before it can send a boot block over it.

The CPU goes around in a dance trying to bring up the primary boot device, read a few blocks from it and transfer control; or if that fails go to the next bootable device.

When the boot blocks are read the bootloader continues and reads in a stage 1 os that fiddles around with the cpu, sets up for multiuser mode and begin the device song&dance again. BSD-Linux etc show this song and dance by presenting all found devices on the screen; and it loads more stuff, either a stage two OS or lots of drivers.

-- mrr