Tandy/Radio Shack TRS-80 Model 4

I've seen boot blocks that contain enough code to print out a message that you've tried to boot a data disc. Trying to boot an unformatted disk in such a machine will likely result in the endless seek. Eventually,

manufacturers moved that functionality into the ROM/BIOS code, but in the PDP-11 days, you could boot a system by writing bits manually into device registers to initiate a transfer of the first part of the disk into low core. I used to know the exact ODT sequence to boot an RL-11 in an 11/24 because I didn't own RL02 boot ROMs. It was about three or four commands. It worked because it takes a human a finite amount of time to enter in all the commands and that gives the drive time to read the block between, like, the third and fourth steps, removing the need to write a boot block that initiates a transfer and loops until the controller shows that the operation is complete. It all comes down to how smart you want the machine to be at boot time versus how flexible you want the booting scheme. -ethan ===== Even though my old e-mail address is no longer going to vanish, please note my new public address: erd(a)iname.com The original webpage address is still going away. The permanent home is: http://penguincentral.com/ See http://ohio.voyager.net/ for details. __________________________________________________ Do You Yahoo!? Kick off your party with Yahoo! Invites. http://invites.yahoo.com/