question for chris on the i/o bus

[John Galt]

I was watching your video on the floppy disk booting.

where you set the boot rom for the floppy with SW3.

I have enabled I/O Bus and reflashed my Due.

Questions:

How do you set things up if you want to use 2 external floppy drives along with Cp/M booting from the hard drive with the floppies on C: and D: ?

Do you need to set the (D) configure disks to none so that they don't try to load off the  SD card?

since the version of Cp/M 2.2 that allows 2 floppy drives uses 330KB disks, 

do you have to use DS DD disks or everything uses HD disks 1.2MB and the monitor on the card kind of handles things when you make a new disk or xmodem copy a disk image over?

did you ever complete the next video on youtube showing the usb port and disk monitor on the Disk controller card?

i'm sure i'll have more questions.

thank you.

[da...@hansels.net]

Hi John,

I can answer the first two questions:

How do you set things up if you want to use 2 external floppy drives along with Cp/M booting from the hard drive with the floppies on C: and D: ?

Do you need to set the (D) configure disks to none so that they don't try to load off the  SD card?

 

Yes.

since the version of Cp/M 2.2 that allows 2 floppy drives uses 330KB disks, 

do you have to use DS DD disks or everything uses HD disks 1.2MB and the monitor on the card kind of handles things when you make a new disk or xmodem copy a disk image over?

The disks on the Altair were 8" DS DD disks, which are equivalent to 3.5" or 5.25" DS HD disks.
So yes, you need HD disks. If you run the disk controller in 88-MDS mode (the 88-MDS used 5.25" DD disks)
then you want to use DD disks.

 David

[Chris Davis]

No, I never created the second video.  Maybe some day!

Be sure to read all of David's notes on the Github page: https://github.com/dhansel/Altair8800-IOBus

David created this controller, I only source the parts and make them available on my site.  I'll be happy to answer questions, but my answers will be based on my experience, not on any specialized knowledge.

Chris

[John Galt]

David and Chris thanks for making these amazing projects.

I'm still in the process of trying to source everything together in one spot.

Does the monitor on the Disk card serial connection work without being connected to the Arduino Backplane, so i can try to run the monitor/diagnostic as i do not have a back plane yet?

in the future, in order to make 330KB floppies i would use the DS DD disks and then upload through the monitor a 330KB disk image, or is i possible to format the disks from cp/m? and how would i do that? is there a "format.com"?

[da...@hansels.net]

Does the monitor on the Disk card serial connection work without being connected to the Arduino Backplane, so i can try to run the monitor/diagnostic as i do not have a back plane yet?

See my answer in this thread: https://groups.google.com/g/altair-duino/c/qW8WSdWn9gk/m/njmovu6ZAAAJ

 

in the future, in order to make 330KB floppies i would use the DS DD disks and then upload through the monitor a 330KB disk image, or is i possible to format the disks from cp/m? and how would i do that? is there a "format.com"?

You need to use DS HD disks if you use a 3.5" or 5.25" drive. Yes, you can upload the image through the monitor.
There is a FORMAT.COM on the CP/M floppy image that comes with the AD. You can copy that onto the HD image
and use it from there. There is also a very fast AFORMAT.COM on Mike's pages:

https://deramp.com/downloads/mfe_archive/010-S100%20Computers%20and%20Boards/00-MITS/41-Martins%20Altair%20Software/AFORMAT/

A good (and a bit more true-to-the-original) way to get an image onto a real disk is using Mike's PC2FLOP.COM:
https://deramp.com/downloads/altair/software/8_inch_floppy/Disk%20Image%20Transfer/

David

[John Galt]

Thank you David,

I understand about the monitor and plugging it into the backplane is the best option from that thread with tom.

Just to be clear on the Disks, 

You always use 5.25" DS HD 1.2MB or 1.44MB 3.5" disks regardless of the size of the disk images your trying to mimic?

[da...@hansels.net]

For the 330K images (88-DCDD) you need HD 3.5" or 5.25" disks. For the 75K images (88-MDS) you need DD 3.5 or 5.25" disks.

In terms of storage capacity, 8" DS DD disks are the same as 5.25" DS HD disks. You can format an 8" DS DD disk to
hold 1.2MB of data.

But the MITS low-level format is not as storage-efficient as the MFM format that allows 1.2MB or 1.44MB on such a disk.
That's why you need the higher-capacity (1.2MB or 1.44MB) disks to store the 330K images.

[John Galt]

got it.

for me i will be sticking to 330K disks so i have a stock of DS HD 5.25" media.

one piece at a time :D

[da...@hansels.net]

Just remembered that the MITS format is single-sided so technically you don't need double-sided disks,
single-sided HD would be sufficient - but I don't know if those actually exist. Of course it doesn't hurt to use DS.
Only one side of the disks will be used though.

[John Galt]

So you could flip over the 1.2MB HD disks and use both sides and get a two for one like the old days?

[da...@hansels.net]

No because the index hole would be in the wrong location if you flipped the disk over and

the drive wouldn't be able to see it. Some systems (e.g. Commodore 1541) didn't use the
index hole so they didn't care but the AD disk controller needs the index hole signal for
synchronization.

[John Galt]

I have a question on imaging a disk.

does a RAW Image exist of a ready to go 1.2mb cp/m disk so i can just raw write a floppy and sort of bypass the monitor for now?

[da...@hansels.net]

Sorry I don't know of any existing raw images and I don't have the hardware to create one.

[udo....@freenet.de]

da...@hansels.net schrieb am Donnerstag, 4. Juli 2024 um 16:01:49 UTC+2:

Sorry I don't know of any existing raw images and I don't have the hardware to create one.

On Thursday, July 4, 2024 at 2:00:29 AM UTC-4 John Galt wrote:

I have a question on imaging a disk.

does a RAW Image exist of a ready to go 1.2mb cp/m disk so i can just raw write a floppy and sort of bypass the monitor for now?

I usually use dd to create a disk image file with the correct size and then format that with mkfs.cpm,(cpm tools), mformat (dos tools) and the like. After filling the image with the wanted files it can be written to a floppy disk with dd or whatever tool is available. 

[John Galt]

its been great so far...

i wish the Reset and monitor buttons were located on top of the board, but i made it work with extensions and external switches.