Altair hard disk controller loads from unit 1 and not from unit 0?

[Harm Munk]

Hi,

There I was playing around with my Altair Duino replica, when a program under CP/M went awry. So, I stopped the Altair (STOP switch), RESET it, and ran the hard disk boot loader ROM. To my astonishment it tries to boot from unit 1 instead of unit 0. According to David Hansel's manual of the Altair 8800 Simulator, it should always boot from unit 0.

What happened? And how do I correct this?

[John Galt]

you have to flip SW0 to change the load order.

or when your in the configuration menu just swap the DSK images for 0 and 1.

so you have to flip FC00 hit STOP-RESET, then Examine, then before you hit run you need to flip everything off and kick SW0 on. 

its a pain, so i just reverse the order of 0 and 1 in the configuration menu for Hard drives.

[Harm Munk]

Thank you, John. To get things running, I did switch the hdisk images.

But some fiddling with the front panel switches showed that you can choose which platter to boot from by using switch 11: SW11=0 boots from platter 0, SW=1 boots from platter 1. I cannot find this anywhere in David Hansel's docs. Am I missing something?

[John Galt]

the information is in the HDBL manual for the rom.

https://deramp.com/downloads/altair/software/roms/custom_roms/M%20Eberhard%20Improved%20ROMs/HDBL%20Manual.pdf

[John Galt]

I don't recommend setting the autoboot with this rom. 

There are issues when you need to do a warm reset with cp/m you forget to reset the panel switches and it starts flipping the boot drive by accident.