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250 MB drives with a Myarc Geneve and a HFDC


Brufnus

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After purchasing one of David Gesswein's MFM emulators (https://www.pdp8online.com/mfm/index.shtml) I set out to test how far I could push our old HFDC.

Having modified it in advance, it was already capable of addressing 16 heads. Since there's a 250 MB addressing limit with the file system, the maximum cylinder count with 16 heads will be 1984. Using only 8 heads, this limit will be at 2048 cylinders (controller limit), giving 250/128 MB respectively.

 

It's absolutely crucial though (which I was also experienced myself during testing), that MDM5 is NOT used for any directory operations; this should be done from MDOS, Directory Manager or something similar. Using MDM5 for this can - and probably will - cause problems later on!

 

I also made an image from my Rodime 3055, a process that worked perfectly as well.

 

Anyway, this emulator is an excellent replacement for failing, noisy, low capacity or unstable MFM hard drives, and has a few other advantages, such as easy backup (can even be automated), low power consumption, and very low - nearly 0 - seek time due to the lack of physical heads, of course. 

 

Hopefully this info will prove useful to anyone wanting to continue using the HFDC with their Geneve or TI. c",)

Edited by Brufnus
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UPDATE: Since David's website can be challenging to navigate, to say the least, and seem to lack some links, here's the address for downloading the latest emulator firmware image (V2.39 is the one I successfully used with mine).

 

http://www.pdp8online.com/mfm/revb/

 

The complete emulator, including a beaglebone, can be purchased directly from David if residing in the U.S. and perhaps Canada; otherwise the beaglebone will have to be purchased somewhere else. There's also a Mouser and a Digikey BOM link on his site for those wanting to build their own board. Note that the board works with both beaglebone black and green editions.

 

If I can be of any assistance with information otherwise, please feel free to ask! :-D 

Edited by Brufnus
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On 10/24/2022 at 9:12 PM, Brufnus said:

UPDATE: Since David's website can be challenging to navigate, to say the least, and seem to lack some links, here's the address for downloading the latest emulator firmware image (V2.39 is the one I successfully used with mine).

 

http://www.pdp8online.com/mfm/revb/

 

The complete emulator, including a beaglebone, can be purchased directly from David if residing in the U.S. and perhaps Canada; otherwise the beaglebone will have to be purchased somewhere else. There's also a Mouser and a Digikey BOM link on his site for those wanting to build their own board. Note that the board works with both beaglebone black and green editions.

 

If I can be of any assistance with information otherwise, please feel free to ask! :-D 

I have purchased a blank board from David and will be working on getting the components for it as well.

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On 10/28/2022 at 12:59 AM, Shift838 said:

I have purchased a blank board from David and will be working on getting the components for it as well.

Great! I'm considering doing the same in the near future; it would be nice to have one of these on the other Geneve as well.

 

Good luck with the project! 

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4 hours ago, Brufnus said:

Great! I'm considering doing the same in the near future; it would be nice to have one of these on the other Geneve as well.

 

Good luck with the project! 

all my components should arrive by late this week or early next and I will build it out.  I did work with Dave to identify newer components that would work as some of there were getting hard to find.  He has updated his BOM on his site for mouser.com

 

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Y.A.P.P.... (Yet Another Problem Pursued):

 

Oh boy, that was a tough one to figure out! c".) I made a copy of my Rodime 43 MB image so that I could format it and transfer my first archives to it (TiImageTool etc. wouldn't read the 250 MB image, so I decided to copy small chunks at a time).

 

However, after having transferred them - no matter what I did, TiImageTool (and TI99dir) showed the old files, rather than the new ones. Then I realized it was because the emulator creates two files when reading a disk for emulation: the raw image and an internal one, which is larger and contains all the data as well. Thus, the raw one I read, was the original one, since a format and/or any file operations leaves that one alone.... :-D

 

Luckily, there's a tool included named "mfm_util", which allows one to create a "raw" image from an emulation file. So I suppose I'll be able to use the 250 MB image after all, once it's been converted that way.

 

Thanks to Beery, I'm now able to transfer everything to the 9640News server via FTP, and the entire club archive which consists of more than 700 files, has just been uploaded. During the next couple of weeks I'll continue transferring and distributing everything in my possession - TI and Geneve programs and utilities, Page Pro pictures, fonts, cartridge dumps, games, and so on.

 

Hopefully some will find it useful, and in any case I think it's well worth preserving as much as we possibly can for these old, but fun computers. c",) 

Edited by Brufnus
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13 minutes ago, mizapf said:

What error message do you get?

Hi,

 

It says "Unknown format or image corrupted". However, I think it was because the image is in the emulator's own internal format... I had the same problem with the Rodime image, but the raw image it created, it reads just fine. So I suppose it will read the 250 MB one as well, once I've converted it.

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7 hours ago, mizapf said:

Emulator means the MFM emulator? Too much emulator in my mind. 🙂

 

If so, yes, you can only open the MAME format with TIImageTool (chd) or the sector dump of all HD sectors (like DSK).

Yes, the MFM emulator.  However, I figured out how to convert it so I'll try that with the big image as well; then it should work. :-D

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Here's another great option with the MFM emulator, which I've just configured myself.

 

Since the beaglebone is running Linux (Debian), it's also possible of course to install and setup a Samba file server.

This makes it even easier to transfer images between a PC and the TI or Geneve.... a simple copy in Total Commander,

Windows Explorer or whatever, with the emulator assigned to a drive letter.

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On 10/24/2022 at 3:08 PM, Brufnus said:

After purchasing one of David Gesswein's MFM emulators (https://www.pdp8online.com/mfm/index.shtml) I set out to test how far I could push our old HFDC.

Having modified it in advance, it was already capable of addressing 16 heads. Since there's a 250 MB addressing limit with the file system, the maximum cylinder count with 16 heads will be 1984. Using only 8 heads, this limit will be at 2048 cylinders (controller limit), giving 250/128 MB respectively.

 

It's absolutely crucial though (which I was also experienced myself during testing), that MDM5 is NOT used for any directory operations; this should be done from MDOS, Directory Manager or something similar. Using MDM5 for this can - and probably will - cause problems later on!

 

I also made an image from my Rodime 3055, a process that worked perfectly as well.

 

Anyway, this emulator is an excellent replacement for failing, noisy, low capacity or unstable MFM hard drives, and has a few other advantages, such as easy backup (can even be automated), low power consumption, and very low - nearly 0 - seek time due to the lack of physical heads, of course. 

 

Hopefully this info will prove useful to anyone wanting to continue using the HFDC with their Geneve or TI. c",)

Nice!  I have a HFDC (and the three headers for drives), and haven't hooked up one of the MFM drives in probably 20 years.  (I have ISA cards too for them).  I'll look into this and getting a board!

 

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On 11/2/2022 at 5:59 PM, acadiel said:

Nice!  I have a HFDC (and the three headers for drives), and haven't hooked up one of the MFM drives in probably 20 years.  (I have ISA cards too for them).  I'll look into this and getting a board!

 

That's a good idea. It's even better than when the MFM drives were new... I'm really glad I decided on purchasing one myself! :-D 

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