Disk Images

[D “DT” T]

Hi All,

First timer here - Just finished building my Altair-Duino pro 3.0 and love it!

In regards to the disk images - I have learnt how to navigate around and load them - all good!

MY question is - Can I load multiple images so that I can have for example a CP/M A:, B: and C: at the same time and able to switch between them please?

Apologies if this has already been answered - I did some searching but couldnt find anything.

KR,

Darren

[udo....@freenet.de]

darren.t...@gmail.com schrieb am Dienstag, 11. März 2025 um 14:49:43 UTC+1:

MY question is - Can I load multiple images so that I can have for example a CP/M A:, B: and C: at the same time and able to switch between them please?

No, this system is build to always boot from drive A: and then it runs what is on the system tracks there. You can put

other CP/M disks in B: ... of course and access files on them, but you cannot boot from B: ... 

[Patrick Jackson]

This is described in detail in the older print manuals for the Altairduino but here's my best telling:

The first 4 LEFTMOST address switches need to be set to determine disk type

The next 4 address switches denote platter/drive (to me its semantics, to others its very important XD )

The RIGHTMOST address switches will be which Disk to mount

So, if I want to mount CP/M with Aztec C hard drive disk image (I have this on my sd card) I will do:

DDUUDDDD DDDDDUDU
to mount disk 5 on platter/disk 0

Then if I want to also mount my own hard drive disk with my tools (its hard drive 7) I will then mount like this:
DDUUDDDU DDDDDUUU
to mount hard disk 7 to disk/platter 1. This will now be drive B:. If I then boot to the hard drive loader, I will boot on drive A: (disk/platter 0, mounted disk 5) and disk B: will be disk/platter 1, mounted disk 7

I hope this helps!

[John Galt]

there is a little bit of a grey area if you have loaded ROMS for the hard drive or floppy where you can change front panel switches and flip which disk you want to boot from, A: or B: could be flipped around on bootup.
i played around with this has i have 2 hacked versions of Cp/M with different settings on hard drives and i can change which one i boot from without swapping things around.

if you use the configuration menu to remap the drives you have a lot more control then punching them into the front panel.

Your not treating this as separate machines where you are multiplexing between them. that is possible if your using the ESP32 Altair emulator, that supports multiple Cp/M sessions i think up to 4. 

you may have seen a demo of the ESP32 altair with cp/m in action and where you got this idea from. Fav posted videos of running multiple Cp/M sessions.

now you can have mapped drives you can have a floppy or a disk image mapped to A:,B:,C:,D: then just change your drive letter to access them as needed.

the CP/M most of play around with support either 4 floppy disks, 360KB or 1.2KB or a combination of 2 hard drive disks, 5mb or 8mb and then 2 360KB floppy disk images.

the 8mb type of hard drive mounting as a floppy disk has its own issues and its better to use the 5MB hard drive images as you have many more options and it isn't worth the extra 2-3mb of storage per drive.

me i just do everything from the Configuration menu setup the disks or swap disks that way without the front panel for most of the setup.

[Tom Wilson]

Yes, you can have multiple images on your SD card, and you can quickly choose which one you want to boot to in the main menu or with the switches. 

Personally,  I think it's a lot simpler to use the menu than to have to remember a bunch of switch combinations:

Hold up START and push the left AUX up, and you get the main menu. In there, I have the disk boot ROM as my Aux1 Up selection, and I have my favorite CP/M disk selected as my boot disk. 

Save that to the default profile with "S".

After that, you can easily switch disks in the menu, then once you have exited the menu, just press Aux 1 Up to boot to that disk. 

[D “DT” T]

Thanks All for your responses. I understand now. 

Much appreciated !!

Darren

[David Williams]

You can certainly have multiple floppy disks, or a hard disk and floppy disks mounted at the same time. You just have to make sure all the drives you have mounted can be read by the OS you're booting. My default profile has the adventure games hard disk and 4 CP/M floppy disks I can either boot the A: floppy and have the 4 floppys as a, b, c, and d, or I can boot the hard drive as a, and have two of the floppys as b and c. Another profile boots Altair disk basic and has a second drive with more BASIC programs.

[John Galt]

i would also point out that even the slightest alteration to Cp/M can result in a disk from another system appearing as blank, garbled or DOS errored.

the disk image can be 100% correct but if the base o/s loaded in memory is not hacked in the same way then it won't work.

there are actually A LOT of cp/m variants out in the wild that you can load on a 360kb or 1.2mb image and 5mb and 8mb hard drive images.

many of them do not interchange disks with each other  and you have to use external methods to extract files and place them on working images for your setup.

[markepi...@gmail.com]

Hey yall,

Since we are talking about mounting and disks, I need to ask.  I;m new at this too.  I cant seem to create a new disk image per instructions.  I mount a non-existant disk image and I can't format it.  If I do a a>b: i get a bad sector error.  not unexpected.  Format shows all kinds of sector, tracks and size data but I get the same kind of errors when I try to switch to b:.  I followed the instructions from Atomic Shrimp on youtube (load CPM on drive 1 and Zork on drive 2) and I can bounce back and forth from a: to b::. How do I create a new disk image so that I can store data and programs on a blank disk?

Thanks

Mark

[Richard Deane]

You could copy a good one and delete the files to create an empty disk.

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