Anyone in the Can/Ontario area with a BeagleBone MFM Reader/Emulator ?

[jc179]

Anyone in the Can/Ontario area with a BeagleBone MFM Reader/Emulator ?

Looking to backup some old DEC MFM drives before they crapout, as I have no backup...

thanks !

 

[Twospruces]

I have an xt with an MFM controller for 20MB hdd. I'm on Ontario. Maybe I could read the files off for you.

 

[jc179]

Thanks for writing - I do too as well, but need to make a more low level backup, the file system isn't fat / PC .

Looking to use use one of these; https://www.pdp8online.com/mfm/

thanks,
Jonathan

 

[ftcnet]

.. also available in Canada from DECromancer (pre-assembled).

 

[maxtherabbit]

Thanks for writing - I do too as well, but need to make a more low level backup, the file system isn't fat / PC .

Looking to use use one of these; https://www.pdp8online.com/mfm/

thanks,
Jonathan

As long as the controller can read the sector headers, it is possible to do a sector level backup on a PC but it requires software which will communicate directly with the disk subsystem. Here is an example of one such software product:
https://fileforum.com/detail/Active-Partition-Recovery-for-DOS/1345740936/2

I'm not sure it will run on an XT though, you'd probably have better luck using a 16-bit MFM card on a 386 or better

 

[hmb]

Anyone in the Can/Ontario area with a BeagleBone MFM Reader/Emulator ?

Looking to backup some old DEC MFM drives before they crapout, as I have no backup...

thanks !

As recommended above, I too suggest you just buy the Decromancer (aka the Gesswein Beaglebone-based MFM hard drive emulator). I have the most recent version currently being sold on their web site.
It is very easy to image virtually any old MFM drive with this device. The instructions provided are a bit cryptic - if you need any help, just ask here.

The advantage of backing up to your own drive emulator is that when the existing hard drive fails you can just plug the emulator, select the drive image file you want it to use, and your system will be back up and running right away. You don't necessarily need to buy enough emulators to replace all your old MFM drives right away - for now you can just buy one, and image all your drives to the same emulator since it has enough built in flash RAM to hold the image file for each of several different hard drives.

 

[Al Kossow]

As long as the controller can read the sector headers, it is possible to do a sector level backup on a PC but it requires software which will communicate directly with the disk subsystem.

It is an incredibly BAD idea to attempt to image a MFM hard disk with a PC controller that has a BIOS rom installed unless you know for a fact that
the disk was written with the same model controller. I do not know of anyone who has successfully done this. I do know people destroying the first
tracks of their disks in their attempts when the controller decides to overwrite data there. Unlike floppies, there are many different on-disk sector formats
on hard disks. Dave's table of them in the reader source code gives you an idea of how many differing ones there are.

A reminder that the write gate signal should be physically disconnected on the cable (or use the write protect jumper on the MFM emulator) when
attempting to image an MFM drive.

 

[maxtherabbit]

That's a good point but to my knowledge only the later XT class 8 bit cards with software defined geometry will ever attempt to write anything to a disk "on their own". Thus why I suggested a 16-bit MFM card (which would be romless) but an older 8 bit card with hard coded geometry settings should also work. I agree of course that physically disconnecting the WG signal is prudent if you're trying to recover anything irreplaceable.

 

[jc179]

As long as the controller can read the sector headers, it is possible to do a sector level backup on a PC but it requires software which will communicate directly with the disk subsystem. Here is an example of one such software product:
https://fileforum.com/detail/Active-Partition-Recovery-for-DOS/1345740936/2

I'm not sure it will run on an XT though, you'd probably have better luck using a 16-bit MFM card on a 386 or better

Thanks, this is interesting, I had tried ghost in the past with MFM drives, but found it didn't work out as I'd expected.
Maybe this is worth giving a shot? I'd always understood different MFM cards wrote to drives differently [be that geometry, or interleave, what not, i have no idea on exact details ] and so using another controller to 'read' that drive wasn't always working.

I do have a few 16 bit MFM cards which work in my 486, maybe ill try giving this software a GO and see if it works any better than ghost did.

thanks

 

[jc179]

As recommended above, I too suggest you just buy the Decromancer (aka the Gesswein Beaglebone-based MFM hard drive emulator). I have the most recent version currently being sold on their web site.
It is very easy to image virtually any old MFM drive with this device. The instructions provided are a bit cryptic - if you need any help, just ask here.

The advantage of backing up to your own drive emulator is that when the existing hard drive fails you can just plug the emulator, select the drive image file you want it to use, and your system will be back up and running right away. You don't necessarily need to buy enough emulators to replace all your old MFM drives right away - for now you can just buy one, and image all your drives to the same emulator since it has enough built in flash RAM to hold the image file for each of several different hard drives.

I would honestly buy this in a heartbeat, but it is a bit steep at $249, for what I see as a 1 off job (unless my present drives do fail, then id be looking to write it back to another set of drives here,, ok 2x 1 off job lol , yeah... ).

The device seems wonderful to be honest, I was also looking at the Qbone as it offers more, but that is even more speeeendy and sort of limited as to what I can put it in. Who knows where the road will lead and if I will have more than 1 system using Qbus in the future.

I do like the idea of the mfm emulator, as it can be used in many more situations..

thanks,

 

[maxtherabbit]

They do write differently. As Al pointed out, there are different sectoring standards. You will have the best luck if you know which brand of ASIC was on the original controller and use a card with the same one.

Geometry is specific to the drive itself and interleave isn't really relevant here, but if the controller can't read the sector headers from the existing format it will not be able to do anything at all with the drive

 

[jc179]

It is an incredibly BAD idea to attempt to image a MFM hard disk with a PC controller that has a BIOS rom installed unless you know for a fact that
the disk was written with the same model controller. I do not know of anyone who has successfully done this. I do know people destroying the first
tracks of their disks in their attempts when the controller decides to overwrite data there. Unlike floppies, there are many different on-disk sector formats
on hard disks. Dave's table of them in the reader source code gives you an idea of how many differing ones there are.

A reminder that the write gate signal should be physically disconnected on the cable (or use the write protect jumper on the MFM emulator) when
attempting to image an MFM drive.

This is a very good tip, I will make sure to disable the write gate signal before trying anything.
Do you figure I can use a romless 16 bit card then ?
Or still probably not going to work?

thanks

 

[jc179]

They do write differently. As Al pointed out, there are different sectoring standards. You will have the best luck if you know which brand of ASIC was on the original controller and use a card with the same one.

Geometry is specific to the drive itself and interleave isn't really relevant here, but if the controller can't read the sector headers from the existing format it will not be able to do anything at all with the drive

yeah, the original controller iirc was built from discrete logic chips, and I wouldn't know which modern asic would perform the same as that.

Looks like I've been-had by the differing sector standards wizard....

May just have to buy the MFM emu...

thanks,

 

[jafir]

(unless my present drives do fail, then id be looking to write it back to another set of drives here,, ok 2x 1 off job lol , yeah... ).

I mean it is an emulator, so if you did have a drive failure, you could use it until you found replacement spinning drives, if you prefer them.

Also a big chunk of the price is the beaglebone and I think you can buy bare boards for the main pcb, so there are probably ways to save some costs. I chose to get the complete tested solution because I have no idea what I'm doing and I didn't want to always be questioning if my assembly skills were the cause of any problem I might have had.

 

[hmb]

I mean it is an emulator, so if you did have a drive failure, you could use it until you found replacement spinning drives, if you prefer them.

Also a big chunk of the price is the beaglebone and I think you can buy bare boards for the main pcb, so there are probably ways to save some costs. I chose to get the complete tested solution because I have no idea what I'm doing and I didn't want to always be questioning if my assembly skills were the cause of any problem I might have had.

For someone (which includes me) buying parts in Canada, I don't think one would save a signficant amount of money by sourcing parts separately and building this emulator oneself vs buying the fully assembled and tested one sold and shipped from a Canadian supplier like Decromancer.

If you replace a failed "real" MFM drive with one of these emulators, you will likely just leave it in place permanently. The emulator is at least as fast, consumes a fraction of the power, operates silently, is easy to back up, and unlike a "real" MFM drive replacement (which would likely be a recycled pre-owned drive with an unknown lifespan) you never again run the risk of failure.

 

[djg]

Also a big chunk of the price is the beaglebone and I think you can buy bare boards for the main pcb,

Yes I sell bare boards which saves some* www.pdp8online.com/mfm. Last i looked ebay had cheap beaglebone greens. I have one green left that I offer for $25 less for assembled. It doesn't have fix for intermittent wired ethernet issue.

* you would need to see if cheaper where you are.

 

[hmb]

Yes I sell bare boards which saves some* www.pdp8online.com/mfm. Last i looked ebay had cheap beaglebone greens. I have one green left that I offer for $25 less for assembled. It doesn't have fix for intermittent wired ethernet issue.

* you would need to see if cheaper where you are.

The cost of shipping from the US to Canada is the problem. It seems almost everything costs at least $25 to ship, so if you need to shop from several different US-based suppliers to acquire all the required parts the total cost quickly adds up. Further adding to the cost for someone located in Canada are the currently lousy $ exchange rate, and the possibility of also having to pay the post office handling fee and "goods and services tax" on each item brought in. I had really wanted to buy the parts from https://www.pdp8online.com/mfm/ and build my own, but in my situation after adding everything up there was little cost saving vs buying the complete tested unit sold by Decromancer.

 

[hideehoo]

Yes I sell bare boards which saves some* www.pdp8online.com/mfm. Last i looked ebay had cheap beaglebone greens. I have one green left that I offer for $25 less for assembled. It doesn't have fix for intermittent wired ethernet issue.

* you would need to see if cheaper where you are.

Thanks for the tip on the cheap greens on eBay! I've been slowing acquiring parts to build a run of these over the last few months, starting with 15F caps on Newark the other day for $0.59 a piece. My JLC boards came in this week, so just need one more shipment on it's way from LCSC. Also did a little LED PCB that plugs into J7. Sounds like this have been done before, but couldn't find any design files.

 

[jc179]

I mean it is an emulator, so if you did have a drive failure, you could use it until you found replacement spinning drives, if you prefer them.

Also a big chunk of the price is the beaglebone and I think you can buy bare boards for the main pcb, so there are probably ways to save some costs. I chose to get the complete tested solution because I have no idea what I'm doing and I didn't want to always be questioning if my assembly skills were the cause of any problem I might have had.

For the moment, I do enjoy having the old physical drives going, they are going to fail one day at some point, so I may as well use them while they're working, and then be prepared to fall back to something else if needed.

I decided to just pickup a MFM emulator kit after thinking further on this, I will inevitably find more uses for it, and may even use it to replace the drives in the system I have here, will have to see how it goes.

Yes I sell bare boards which saves some* www.pdp8online.com/mfm. Last i looked ebay had cheap beaglebone greens. I have one green left that I offer for $25 less for assembled. It doesn't have fix for intermittent wired ethernet issue.

* you would need to see if cheaper where you are.

Thanks for you and the community efforts in putting stuff like this together!
I went for an assembled one, I would have enjoyed building it, but I am more eager to use the emulator than build it at the moment!

thanks,
Jonathan