Compaq Portable Plus

[Cliff Miller]

The mfm emulator has assisted in the restoration of my Compaq Portable Plus.

I read the original 10mb hard drive and saved the emulation file then ran the disk emulator using that file and was able to access the emulated C drive.  Compaq Dos 3.31, Wordstar, Lotus 123, and others - old times.

After repair, the original hard drive will boot the system but the emulated disk will not - the system boots off the boot floppy and the files on the emulated hard drive are accessible but it doesn't support booting.

I've read about others having difficulties with the original Compaq WD hard drive controller and to date have not found a low level format option for it so creating emulated drives of sizes other than the original cannot be used.

The floppy is a Gotek emulator using Flashfloppy firmware and various OS that I've found an image for.

What will not work - Spinrite just dies.  MS-DOS sys command generates seek errors as does the format command.  

My use of the mfm_emulator is very elementary and I thank everyone for the questions and answers on the forum.

[David Gesswein]

Checked mine and it has SMC/OMTI controller so can't directly test anything.

Assume this is the card you have?
https://www.ebay.com/itm/175844688445

Are you using the latest code? I made a fix recently that may help.

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[Cliff Miller]

David - My controller is identical to the photo you referenced.  It has a Compaq part # and a WD chip. The second 40 pin chip is Texas Instruments IIRC.

I flashed my BBB with the BBB-mfm-emu-v4.20-OS-11.8-r74-flasher.img before I started this exploration.  Are there updates beyond that?

[Cliff Miller]

My controller is identical to the one in the photo but has no external connector and cable.

The software is the latest version.

I copied the image of the original bootable hard drive but the Compaq only boots off the Gotek with an image of Compaq Dos 3.31.  I manually erased all files and directories on the C drive (image) and copied the Compaq Dos files from the floppy image.  "Copy A:*.*" worked smoothly accessing the emulated hard drive.

"Sys c:" refused to complete with numerous "Boot/Retry/Fail" errors.  "Format c: /s" also errors out.

"Fdisk" runs and shows a normal active DOS partition marked Active.   

"Spinrite" launches and shows nothing on the screen for a number of minutes. It requires a power cycle to restart the computer.

I am getting non-zero glitch counts when commands fail.

On Thursday, May 16, 2024 at 7:32:41 PM UTC-4 d...@pdp8online.com wrote:

[Cliff Miller]

I found another copy of the Compaq Portable Utilities Disk.  Originally I found no low level format utility.  The menu has 3 items - setup, inspect and test.  Setup would error out saying "This disk is not for this computer" or something similar.

I launched the image of the original 10mb hard drive on the mfm emulator then booted the Compaq from the Utilities Disk image on the Gotek.  This time I tried the "Inspect" menu. The program found the emulated fixed disk and it tested successfully.  Down another layer I found the format option and watched as the program went through every cylinder and then did a read and compare successfully.

Exiting the format menu I found the emulated hard drive to be working completely without exception - fdisk, format  and sys commands executed and the console showed the emulation responding without error.

David's instructions describe how to create an emulation file and then to run the low level format for that controller.

Once I discovered the Compaq format menu the instructions worked for me.

"Format /s" and "Sys" created a hard drive that boots perfectly.  I may have run "fdisk /mbr" in there somewhere - my DOS knowledge is a bit rusty.

[d...@pdp8online.com]

Good to hear its working with fresh format. Quickest may be copying what you want onto the new image. Looks like your controller doesn't support two drives do can't have the other image as second drive. It is strange that the original disk boots but the copy of it doesn't. I assume the repair you referred to is hardware and not something done to the disk after the image was made. Remote debugging is a slow process but if you think its worth the time we can poke more at your original image. Haven't had other reports so seems to be specific to your setup.

[Cliff Miller]

The repair I mentioned was prior to any use of the hard drive.  "The Phintage Collector" on Youtube described a repair of a hard drive that seemed identical to mine - it required the removal of the drive electronics to access a magnetic coil and latching mechanism which had become stuck to the exposed portion of the drive platter.  I copied his actions and it permitted the drive to rotate and to operate seemingly properly.  Like him my computer booted from the drive after freeing the platter.

https://youtu.be/7qrmHv9XFdg?feature=shared

I was excited to get an image of the drive as soon as I realized it worked well enough to be read.

[Cliff Miller]

Thank you for your reply.

You mention the inability to run a second image for transfer purposes.  

Is there a way to mount the emulator images on the Beaglebone to transfer files between them?

Cliff Miller
cli...@gmail.com

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[David Gesswein]

Sort of. The emulator image is raw MFM encoded data. Only think I know that
can use it directly is TRS-80 emulator trs80gp.

I do provide tools to convert from/to a disk image. To make a disk image
do something like

$ mfm_util --emu emufile --ext dosimg.ext --ana

It will print something like this. You will need information from it later.

Interleave (not checked): 0 3 6 9 12 15 1 4 7 10 13 16 2 5 8 11 14

Command line to read disk:
--format OMTI_5510 --sectors 17,0 --heads 6 --cylinders 640 --header_crc 0x2605fb9c,0x104c981,32,6 --data_crc 0xd4d7ca20,0x104c981,32,6 --sector_length 512 --retries 50,4 --drive 0

For disks that are partitioned tools I use need the partitions extracted. You
can do that with following. All is assuming you are using my latest OS image.

Just become root.
$ sudo su

# kpartx -av dosimg.ext
add map loop0p4 (253:0): 0 65161 linear 7:0 17

If you want the parition to use with tools not on the beaglebone you can
create a file with
# cp /dev/mapper/loop0p4 partition1
You can then use scp to copy file off or copy to removable flash on beaglebone

On beaglebone you can try to mount the partition


# mount -o loop /dev/mapper/loop0p4 /mnt/usb
usb is an existing directory. You can use any under /mnt or create one.

Do the same for other image except pick a different directory under /mnt

Should see your files
# ls -l /mnt/usb

After moving files umount everything
# umount /mnt/usb
#kpartx -dv dosimg.ext
Do same for second image you mounted

Now you need to convert back to emulator file. Go back to debian user
# exit

$ ext2emu --format OMTI_5510 --heads 6 --cylinders 640 --interleave 3 --ext dosimg.ext --emu new.emu

For interleave enter the value from subtracting the first two values reported
from mfm_util (3 - 0).

May want to try this command first to verify if your format is supported. Also
see if it still boots ok before you change anything.

mtools is on the beaglebone also. If mount and copying files makes image
ususable by Compaq you can try mtools.

mdir -i partition1 ::
To copy all files to current directory
# mkdir workinge
# cd working
# mcopy -spm -i ../partition1 :: .
To copy all files in current directory to image
# mcopy -sp -i ../partition1 * ::

You will need to copy partition1 back to /dev/mapper/loop0p4 before kpartx -dv

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