DPU System with Compact Flash Disk

[grahamlees1]

Hi Folks,

Short Version:

I now have a DPU, MCU, 512MSU, 16FDC, TUART system running Cromix Plus 162 using solid state storage on a S-100 CF/IDE Card . 

Thank you to Damian Wildie for writing the CF/IDE driver and helping me setup the system.  Thank you to all who helped me work through various issues with the system, to the folks who run this group, and everyone who has contributed to and organised the github repository.

Long version:

About 18 months ago I was lucky enough to acquire a box with a couple of dozen S-100 cards, a couple of empty chassis, some 8” drives and several hundred 8” disks.   I had no idea if they were related but I felt like all of my Christmases had come at once anyway.

There were several Cromemco boards (but no Cromemco chassis or drives). I could see that Cromemco was were well supported by this community.  The github archive is awesome and the people very helpful. 

I had the following configuration:

· a DPU
· a MCU
· a 512MSU
· a 16FDC
· a TUART

I spent a lot of time getting the MSU card sorted (a single board computer was surprisingly useful).  I replaced over 20 RAM chips.  With some help from people here and the images in the github repository I got Cromix and then Cromix Plus running on an all-floppy disk configuration (one gotek, two 8” Mitsubishi drives and one 5.25” Mitsubishi drive.

The slow speed of the system (the drive chatter is great!) was tolerable but I couldn’t properly install some of the compilers etc because the installers used links which on my system failed because of the separate physical volumes.  No surprise as Cromix is really intended for hard disk installation.

I went looking for hard disk solutions.  We don’t see many Cromemco hard disk controllers down in South Australia and finding a suitable disk would have been difficult.  In any case reliability would have been an issue.

Searching the group I came across Damian Wildie’s solid state storage solution.  It uses a modern S-100 CF/IDE card (designed by John Monahan) combined with a Cromix driver written by Damian.  Damian has also created some other tools such as cromix-fs for transferring files to cromix disk images and the Cromix Plus Emulator.

I contacted Damian (conveniently located only 1000 miles and one timezone away), and he very generously agreed to help me get his solution up and running on my configuration.  Damian sent me a hard disk image for me to write to a CF card.  He also sent the 162 cromix.sys customised for my system on a floppy image.  I moved it to a 40 track image  because I have an old RDOS. 

I was fortunate to find a PCB for the CF/IDE card.  Some of the parts are a bit hard to find in the antipodes so it took about a month to get the card together.  Once I shook an error out of my build and a defect from a CF card adapter (Damian helped find that too) the image just worked.  I now have three hard drives of about 150MB each on each of two CF cards.  This is way more storage than i will ever need.  Damian even put a special gen folder on the hard disk image so that I could customise a little more eg I added the TUART.

The IDE drive has a major device number of 12.  I boot off the 5.25" 40 track floppy image on the gotek and then select 12,0 as the root drive.  Additional drives can be easily mounted after boot.  Once booted, the gotek can be used to feed up 5.25" and 8" images from the archive or created with cromix-fs.

The CF image is not bootable and the tools aren’t there to set up a drive from scratch but these are not great limitations.  My system memory is limited to 512k and that doesn’t seem to be enough to run a file system check on 150MB drives (I haven’t tried smaller).  On the plus side, I can image the CF card on my pc to back it up – a process that takes about 10 minutes.

I've had a great time installing a bunch of compilers and testing with the obligatory “hello world”.  I’ve pulled across a few CP/M apps as well using cromix-fs eg wordstar, dbase, multiplan, supercalc, turbo pascal, and zork.  The system supports three terminals but I’ve learnt that two concurrent CP/M programs can really slow things down!  512k is a bit limiting for multitasking the 68000.

Unfortunately, I don’t have a beautiful old terminal (let alone a Cromemco) so I’ve been using an IBM terminal with Televideo 925 emulation.  The 925 is supported by Cromix Plus and most CP/M programs.  Kermit also supports it.

Lots more things to try.

A few images attached.