Which CP/M BOOT .DSK is Best ???

[Walt Perko]

Hi, 

Considering there are multiple CP/M BOOT .DSKs ... CP/M 2.2?  CP/M 3.0?  

I'm wondering Which is best for:  

A basic Altair 8800c or even original Altair 8800 computer with an 8080 CPU board?  

How about an Altair using a Z80 CPU?  

How about using the ESP32 FDC+ WiFi modules v. FDC+ Serial Drive Server on a PC?  

Are there direct links to download the .DSK files?  

.

[Walt Perko]

Hi, 

I forgot to mention, those questions would be good for discussion in the next ZOOM on Sunday.  

.

[Patrick Linstruth]

I think the answer is, “it depends”.

Assuming an FDC+ for your disk controller, I would use the following:

1) Real 8” floppy drives: Mike’s buffered CP/M 2.2.

2) Real 5.25” floppy drives: Mike’s 1.5MB CP/M 2.2.

3) Serial Drives: Mike’s 8MB CP/M 2.2

I see no benefit to using CP/M 3 for what I do.

I don’t think there is any difference between using a Z80 or 8080, other than inherent Z80 performance improvements, since all the CP/M images for Altair I know of are written for the 8080. Some CP/M images will not work with a Z80 since the timing is dependent on a 2MHz 8080.

All of the Altair CP/M images I’m aware of require a 2SIO and Altair-compatible disk controller like the FDC+. If you’re wanting to use any other hardware, like boards from s100computers.com or a JAIR, then none of these images will work as none of them support “standard” interfaces.

So, it depends on your hardware and what you’re wanting to accomplish as to which CP/M is best.

I have started a repository of disk images for various disk controllers, but all need a 2SIO. Since this is project that is currently under development, content is subject change without notice and the documentation has not been written yet.

https://github.com/deltecent/altair8800-packages

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[Walt Perko]

Hi, 

My questions are for a more basic Altair 8800 computer using only a front panel, a CPU board, a RAM board and an 88-2SIO (JP or R1 or MITS Original) ... connecting to either the FDC+ Serial Drive Server running on a PC or the  ESP32 FDC+ WiFi module.  Connecting the console to either a terminal emulator on their PC or a real dumb terminal that doesn't require more than a simple Rx/Tx exchange of data.  

This is what I figure is the best starting point for newbies or even people with plenty of experience building a new Altair 8800 compatible computer.  

Later, people can look into adding various external devices to their working system one piece at a time ... like a real floppy drive, or a video console board, or other devices.  

The idea is getting a basic system up 'n running and having a choice of a .DSK file for BOOTing their system.  

.

[Joseph Corda]

Good questions Walt .. along those same lines 
I would be interested in: 

• Learning more about the basic steps needed to be modified in CP/M 2.2 BIOS for adding a different SIO and FDC controller 
• For example a Cromemco TUART (or CompuPro interfacer 1) and CompuPro Disk 1 FDC) to a basic Altair 8800c system.   
• is there a CP/M 2.2 source that is recommend as a good starting point ?  
• Lifeboat, Mike's Altair CP/M ..etc
• Has anyone used SIMH Altair8800 or Altairz80 as a test base for CP/M BIOS changes? 
• Honestly I would think adding the TUArt and DISK! as virtual hardware would be my block point here

As I see it, being able to get different brands of cards to work under CP/M seems like a powerful skill.

Joe

To view this discussion visit https://groups.google.com/d/msgid/Altair-8800/b0fa7abc-028b-4b6b-bd78-fd82f99c9c6bn%40googlegroups.com.

[Patrick Linstruth]

• Has anyone used SIMH Altair8800 or Altairz80 as a test base for CP/M BIOS changes? 
• Honestly I would think adding the TUArt and DISK! as virtual hardware would be my block point here

Lots of times. TUART and DISK1 both exist on AltairZ80 simulator. TUART is SIMH TMXR compliant, so you can connect a real serial port and do Xmodem transfers (steps 3, 7 and 8  below).

I have not ported them to Altair8800 yet.

The 8MB Serial CP/M BIOS was done completely on the simulator. I also used the simulator to create Tarbell Double Density CP/M from the Single Density CP/M following Tarbell’s instructions. The BIOS for the JAIR was enhanced and all work was done on the simulator. The 8MB CP/M CBBS BIOS for PMMI and JAIR were done on the simulator. I am fairly sure Mike Douglas used the simulator when getting CP/M and FDOS working on iCOM hardware. The simulator is a big time saver and being able to dump memory, single step, set breakpoints, and see a history of instructions and registers is a real blessing.

Usually the steps I use are something like:

1) Consider writing a disk exerciser (AFEXER) for the new hardware since a lot of that functionally (drive select, seek, read/write sector) is needed for the loaders and BIOS. Real hardware can also be tested.

2) Get ROM boot loader, CP/M track 0 loader, and CP/M running on the simulator. This may require creating disk images with a hex editor. I often use the 8MB Atlair CP/M for assembling and building files to hexload and put on the new disk.

3) Port PC2FLOP to the new hardware configuration using the simulator. A stand-alone FORMAT program may also be necessary if non-standard format.

4) Transfer the disk image to a formatted floppy

5) Burn ROM or hexload loader

6) Hope it boots - wash, rinse, repeat if no boot

7) Port PCGET and PCPUT to new serial hardware using simulator, then real hardware

8) Port FLOP2PC to new hardware using simulator, then real hardware

You can never go wrong starting with anything Mike Douglas has done. I would start with a BIOS that most closely matches the hardware you want to use. You may also be able to mix and match; use parts an existing BIOS with DISK1 support and another BIOS with TUART. With IOBYTE, you can make a BIOS that supports 2SIO and TUART at the same time.

A good place to start is here:

https://deramp.com/downloads/mfe_archive/040-Software/Digital%20Research/CPM2-2/Manuals/CPM_2.2_Alteration_Guide_1979.pdf

To view this discussion visit https://groups.google.com/d/msgid/Altair-8800/CAACXqMfg%2BEAY76Luu%2B5LLZhRTrDfZwaP2cii2bmsHkGayHdeEg%40mail.gmail.com.

[Joseph Corda]

Thanks Patrick

This was exactly what I was looking for...   .

Glad to hear the SIMH is being used so much .. I used it as well when developing JoeMon .. and it work great for that 
I will reach out directly if I have any questions.

Joe

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