H8D vs. H17 disk images

[Joe Travis N6YPC]

Greetings All,

I tried searching the archives but failed to find a definitive answer.  Are the H8D and H17 disk image formats compatible?  I've seen a number of disk images listed as H17 and wondered if it was just a name change or if something other than the 10 (hard) sector, 40 track, single sided is used / supported (e.g. 80 track, double sided)?  Is the H17 format recognized by the (current, old) H8DUtility?

Thanks,

Joe Travis n6ypc

[Glenn Roberts]

They are different.

H8D is simply a linear copy of the user data on the disk, in 256-byte sector chunks. The first 256 bytes is track 0, sector 1, then track zero sector 2, … up to track 39 sector 10 for an H17 image. The file will be exactly 256 * 10 * 40 = 102,400 bytes long. Double-sided disks would be twice that, and 80-track disks twice again.

The H17 format was developed by Mark Garlanger and contains more physical data per sector, such as timing bits, plus metadata such as descriptive text. From an archival perspective it is a digital capture of all the bit streams on the disk and a mechanism to document the physical characteristic of the disk and it’s contents.  The exact file specification is documented here

https://heathkit.garlanger.com/diskformats/H17Disk-draft.pdf

Mark has a utility that can convert from H17 format into the simpler H8D. It runs under Linux or MacOS.

Sent from my iPad

On Nov 20, 2021, at 11:23 PM, Joe Travis N6YPC <jtravi...@gmail.com> wrote:



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[Richard Davis Jr.]

Travis,

I have used various h8d images and the h8dutility with no issues.

I am using softsector disks with a hard sector emulator board. It emulates a hard sector floppy by generating the sector pulses.

Rick

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[Joseph Travis]

Thank you for that explanation Glenn. I had seen some titles in H17 format I was interested in that I hadn't seen in the H8D format.  Unfortunately, I don't currently have a Mac or Linux machine.  Is there hope for Windows?

Regards,

Joe Travis n6ypc

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[Russ Price]

Hi Rick,

Is it the virtual sector generator board  from Deramp (Mike Douglas)? Or from a different source?

Russ

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[Richard Davis Jr.]

I belive so. It's the only one i found you could purchase as a kit or assembled.

It comes with a 9v batery holder. I didn't use that.  just covered the bottom of the board with electrical tape and connected power to the h8 +8v and ground and laid it on top of the capacitor cover.

Works great.

Rick

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[Russ Price]

Awesome. I bought the same kit.  Glad to hear it works well. 

Russ

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[Mark Garlanger]

It should be easy to get the tools to run under windows. Most of the file conversion code is just C++. I just don't have a windows

 development system setup. 

Which titles were you wanting? I could convert them for you. 

  

I was thinking that for each disk image, I would provide them in 4 versions, H8D, h17disk, h17raw, and a zip file with all the files 

extracted. The h17raw format is each sector with everything including the padding, sync bytes, checksum bytes, and 

the header. Sectors are padded to 320 bytes. h17raw would be a simpler format than h17disk, but it still has all the header info

that is missing in the h8d format. 

Mark

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[Joseph Travis]

Hi Mark,

Thanks for the offer. Some of the titles I'm looking for are:

Software Toolworks: HDOS  8080/Z80 Macro Assembler, Ed-A-Sketch

Apogee Software: HDOS  Froggs, Robot_Battles

I'm in no hurry.  If you were to make them available on your website sometime in the future, I'm sure others would appreciate them as well.

Thanks again,

Joe Travis n6ypc

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