Category: CP/M

About CP/M

Machines that run CP/M or a related OS such as TurboDOS.

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Using Greaseweazle with Sorcerer/Micropolis Disks

Posted on by Graham

The Micropolis disk system uses hard sectored disks. This is particularly challenging for disk imaging systems.

Release 1.20 of Greaseweazle included hard sector support, so i gave it a try. I was able to read and write disk images with moderate success. Without a codec for the disk formats the software could not check each track and retry if necessary.

The Greaseweazle developer, Keir Fraser offered to add the fluxengine codec into the code which he did very rapidly.

I tried it out and found it worked very well.

I did find that some of the default parameters didn’t work well with my drives, but these were changed with the delays option.

The relevant commands are:

Get helpgw -h
Speed testgw rpm –-drive=0
Head cleangw clean –-drive=0
Set some safe drive parametersgw delays –-step=30000 –-settle=10
Reads a micropolis disk into an scp file.  The raw option keeps the sector pulses and allows reprocessing.  Without the raw option the files are more easily viewed with the HxC tools.gw read –hard-sectors –-drive=0 –revs=5 –tracks=”c=0-76:h=0″ –-raw %1.scp
Writes a micropolis scp file to a diskgw write –hard-sectors –-drive=0 –tracks=”c=0-76:h=0″ –-raw %1.scp
Reads a SS 100TPI 256 byte sector micropolis disk and decodes it into an IMG file.gw read –hard-sectors –drive=0 –format=micropolis.100tpi.ss –retries=8 %1.img
Writes a SS 100TPI 256 byte sector micropolis IMG file to a diskgw write –hard-sectors –drive=0 –format=micropolis.100tpi.ss –retries=8 %1.img
Reads a SS 100TPI 275 byte sector micropolis disk and decodes it into an IMG file.gw read –hard-sectors –drive=0 –format=micropolis.100tpi.ss.275 –retries=8 %1.img
Writes a SS 100TPI 275 byte sector micropolis IMG file to a diskgw write –hard-sectors –drive=0 –format=micropolis.100tpi.ss.275 –retries=8 %1.img

CP/M files are read with the 256 byte option format=micropolis.100tpi.ss

When creating the image files, the sector integrity is checked and if the sector is bad it is retried. It was common for multiple retries to be required.

I did try to adjust some parameters (i had to with fluxengine) but i could not get much improvement. Nevertheless, it was quite satisfactory.

The actual system does better, so it often helps to make a fresh copy of a disk on the Sorcerer before trying to image with either FluxEngine or Greaseweazle.

I also tried using Greaseweazle to write micropolis images to soft sectored disks with a Virtual Sector Generator. It also works fine.

What i have not been able to do, so far, is to trick the Sorcerer into using a Gotek/Flashfloppy either with or without the Virtual Sector Generator.

As at V1.22 Greaseweazle includes the micropolis codec.

I use Greaseweazle a lot so i really appreciate the effort that Keir and others have put into its development.

Sorcerer ROMPAC Basic Games on CP/M

Posted on by Graham

There were a number of games on the Sorcerer disks that fired up fine, but there were a large number that did not.

I got some help from Alan Laughton (Microbee Technologies) to work out what was going on. He spotted that the files contained basic. They were com files – so quite different from the basic files that you would load into the disk basic.

Browsing through the manuals and other data, it became clear that the ROMPAC BASIC work area had been set up in such a way as to allow programs to be saved and loaded with CP/M.

The ROMPAC basic has a lot more memory available to it than the disk basic. It doesn’t waste space on the interpreter or the operating system.

The first entry in the com file is a jump to the warm start area of the basic ROMPAC. This failed on my machine because i had no ROMPAC.

What i did have, though, was a 8k S-100 RAM card (Solid State Music MB6) which i could locate at the same address as the ROMPAC at C000.

The card, predictably, failed the Sorcerer Monitor RAM test, but the offending IC was found and replaced.

I tested it out by using ddt to load the ROMPAC which was moved up into the RAM card. Following reset, the “RAMPAC” was found and basic fired up.

“bye” at the basic prompt returned to the Sorcerer monitor and GO BC00 started CP/M again. One of the previously failing com files was loaded and sure enough it ran!

After that, i wrote a very short program that replaced the ddt step. This allowed another 23 games to execute.

I’ve since created to couple more which load the development and word processor ROMPAC code into the RAMPAC.

The memory card had a facility to write protect the contents, so i added a switch to the expansion unit to enable it.

Transferring ROMPAC Basic Programs from CP/M to Tape

Posted on by Graham

Some of the basic games that have been stored as CP/M com files are missing from the sorcerer archives at Microbee Technologies (Alan Laughton is the curator) so i went through the process of transferring them back to audio files.

These were translated to wav files as follows:

  1. At monitor GO BC00 to boot up CP/M.
  2. Load the basic rompac (LDRAM).
  3. Reset – starts basic.
  4. Bye to return to monitor.
  5. SE T=1 to set 300 baud.
  6. GO BC00 to boot up CP/M.
  7. Load up the game eg A>LAIR to load up LAIR.  This starts up the ROMPAC basic.
  8. Load up Audigy on a PC.
  9. Set recording gain to max and the input to mono.
  10. Connect LINE IN on PC to AUX on Sorcerer.
  11. Start recording and enter CSAVE LAIR.
  12. When the sorcerer comes back with READY stop the recording and trim if necessary.
  13. Apply a good 20dB of gain to maxout and square up the waveform.
  14. Export the audio to a wav file.

Check as follows:

  1. Connect the PC LINE OUT to the input of the external amp.
  2. Connect the external amp output to the EAR input of the Sorcerer.
  3. Set Audigy playback volume to max. 
  4. Watch the EAR input with a scope and back off the Audigy volume until the waveform is clean and square.
  5. CLOAD LAIR.
  6. Hit play on Audigy.
  7. The title should be shown in less than 30 seconds.
  8. By the time the audio is complete, the sorcerer should say READY.
  9. RUN and enjoy.

If you want to do another then breakout with ^C, BYE to return to monitor and GO BC00 to boot CP/M.

Ampro Little Board Plus

Posted on by Graham

This is one of my current projects. It is based on the Ampro Little Board Plus which is a single board computer designed to be mounted on the back of a 5.25″ floppy disk drive.

It uses a Z80 processor running at 4MHz and includes two serial ports, one parallel port, a floppy disk controller and a SCSI controller. It runs CP/M 2.2 and is happy to boot off a floppy or hard disk. I’ve added a SCSI2SD to emulate several 20MB hard disk drives.

The user interacts with the machine using a serial terminal.

I started off with the two 40 track Mitsubishi drives shown but have been using a gotek (with FlashFloppy) for the software load.

Currently, i’m loading up a whole bunch of software from images created using cpmtools. Eventually this will be mounted in an external drive enclosure.

Adding SCSI2SD to AMPRO Little Board plus

Posted on by Graham

I used a scsi2sd card with a 256MB sd card.

This took me a bit longer than I expected because I didn’t read the instructions.  CP/M needs to be configured to have some hard disk buffer space, otherwise the format fails mysteriously.  I changed it from 60k to 56k.  That allows room for the maximum 88MB of total disk storage.

The hformat program allowed for different controllers but after some experimenting I found success with the Seagate ST-225N hard disk. 

+-----

Form                 5.25"/HH              Cylinders     615|     |     |

Capacity form/unform    21/   25 MB        Heads           4|     |     |

Seek time   / track  65.0/20.0 ms          Sector/track   17|     |     |

Controller           SCSI1 SINGLE-ENDED    Precompensation

Cache/Buffer               KB              Landing Zone      670

Data transfer rate          MB/S int       Bytes/Sector      512

                      1.500 MB/S ext ASYNC

I set up sd2scsi with 7 drives each with 615 x 4 x 17 = 41820 sectors of 512 bytes.

I used hinit (with burst mode) to set up 2 partitions on drive 0 and drive 1:

  • 8192k
  • 8192k

This needs to be done on every boot (really? yes) but an alias can be created:

alias

HINIT YD010 AF8192 AG8192, YD110 AF8192 AG8192,.

hardinit

then another alias that does this and swaps the drives over:

alias

HARDINIT; SWAP AF BG CH DI; STARTUP

HSTART

Startup can contain whatever is wanted, eg a menu program.

HSTART can be run on boot by adding at item 5 in the config program.

Copy the system track from the boot floppy to the hard disk using SYSGEN (watch out for the letter swapping).

Less than obvious (it’s in a separate section of the hard disk software manual right at the end) are instructions for autostart, noting HGEN in particular.:

When the system starts, it looks for a boot floppy. If it finds it, then it will boot from it.  If it doesn’t find it, in about 10 seconds it will boot from the first hard disk partition.  For some reason it keeps looking for a disk in the first floppy disk drive.  If you give it one it stops but does nothing with the disk.