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To Win Hill

Hi,

Just a follow-up for anyone else attempting to make a backup of their

5-1/4" HP4145A Boot diskette.

I was able to make a few working backups using an old 486-33Mhz clone PC with a 1/2 high 5-1/4 1.2MB diskette drive. My best results were with "TeleDisk" Version 2.12 I used an original 4145A Rev A5 diskette tor the tests. Teledisk reports the disk format as single sided 40 tracks 9 sectors at 256 bytes per sector. (Soft format) ~90 Kbytes.

I made three image files with teledisk, two produced working copies but only one gave me 100% working copies. It appears from looking at the image files that the first sector may have been partly read and aborted on the images that were not 100%. After the extra data at the start the rest of the file matched the 100% working image. I did use a bulk eraser on the diskettes before the copy operation to remove any previous formating information.

I did try a copy board and copyiipc but these seem to be try too hard to make a bit copy (including slack area) and the copies were unreliable)

Hope this helps someone else, Nitro

Reply to
Nitro
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Also consider OmniFlop

formatting link

Reply to
Homer J Simpson

One issue that might be at play here is the newer higher-density floppy drive's head gap and its magnetization-field intensity and shape. The older heads likely had larger gaps with fields extending further from the gap for the purpose of reaching deep into the thick magnetic oxide on the old disks. The newer drives have smaller head gaps. OTOH, presumably you are making your copies on new floppies with thinner oxide layers, designed to be used with newer drives. But, will the old drives in the 4145A be happy with the new disks? Hmm. What's your 4145A success rate making one floppy after another on the PC, using the 100%-working image file?

--
 Thanks,
    - Win
Reply to
Winfield Hill

I did think of that having trouble with it in the past. The floppys are old re-used floppies. The drive is an older but not ancient 5-1/4 drive capable of the 48 or 96 TPI format up to 1.2MB. There was a change in the corsivity between the 48 and 96 TPI diskettes but the drives were designed to handle both types of diskettes. Even the new 5-1/4" floppies are made to the same specs for compatibility with the existing drives. By bulkerasing the floppy first I was attempting to remove any stray inter-sector data that may have been recorded on the diskette prior to the new format. I was targeting mainly sector timing information but this also aids in problems caused by head write width and track position errors from any previous data. Most drives can read slightly off track data as long as the side noise is random.

The copies from the "good" image were 100% working on the 4145A (6 of 6) for the boot operation and a disk catalog read. I did not try a full diskette test as there is no function on the 4145A but I did try a random file read on them with sucess.

Regards, Nitro.

Reply to
Nitro

only

files

images

file

diskettes

you

designed

Probably good. One key point is to bulk erase the disk before to get rid of the extra field the thinner HD heads can't erase. But the 4145A may not write on such disks (Hc of an HD floppy is about twice of a SD/DD one).

--
Thanks,
Fred.
Reply to
Fred Bartoli

I still have almost 1000 new Sony SS/SD 5.25" floppies on hand. They are packed ten to the box, and ten boxes to the case. I also have about

100 5.25" disk drives in storage. 
--
Service to my country? Been there, Done that, and I\'ve got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
Reply to
Michael A. Terrell

eBay is your friend.

--
 Thanks,
    - Win
Reply to
Winfield Hill

I was saving them for my old Commodore computer collection and some test equipment, but I am willing to share them, cheap. I doubt that I could sell them as a single lot on eBay, so I'd have to sell them in a bunch of small lots. I have about 200 in the house. The rest are buried somewhere in storage right now.

--
Service to my country? Been there, Done that, and I\'ve got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
Reply to
Michael A. Terrell

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