• Please review our updated Terms and Rules here
  • Exhibitor application for VCF West 2022 is now open! If you are interested in exhibiting, please fill out the form here.
  • Here are the results of the VCF East 2022 Post Event Survey: Survey Results

5.25" Hard Sector Floppies

deramp5113

Veteran Member
Joined
Mar 9, 2013
Messages
881
Location
Dallas, TX
As discussed in several threads recently, hard sector 5.25" disks - especially the ten sector disks for North Star controllers - are getting very hard to find.

I now have a working prototype of a virtual sector generator that connects onto the 34 pin ribbon cable (in-line or just an extra socket pressed onto the drive cable) that makes soft sector floppies look exactly like hard sector floppies to the controller. The board syncs to the rotational rate of the currently selected drive and generates sector pulses to the controller so the controller can't tell the difference. It has been working very reliably, even with the older, full-height, belt-driven drives. The board requires no external power connections and is very unobtrusive - barely wider than the drive cable.

For example, with the board clamped onto the drive cable, an original North Star system with original drives can work transparently with hard or soft sectored disks.

I'm going to finalize the layout and run a panel of the boards. I'll probably get 20 or so boards off the panel for those who are interested.

Mike
 

Nama

Veteran Member
Joined
May 22, 2009
Messages
684
Hi Mike,
This sounds great,
Please count me in for one unit, and depending on the price I may get two.

Thanks
 

jgalinat

Member
Joined
May 25, 2012
Messages
36
Location
Tucson, AZ
Hi Mike,
I would love to have one. Please put me down for one. That way I could recreate my first system, an IMSAI with a Northstar Floppy Controller. The thing holding me back was the non-availability of the media. This would obviously solve that.
Jeff Galinat (proud owner of an Altair clone)
 

pbirkel@gmail.com

Experienced Member
Joined
Apr 7, 2013
Messages
438
Location
Silver Spring, MD, USA
Hi Mike,
I would love to have one. Please put me down for one. That way I could recreate my first system, an IMSAI with a Northstar Floppy Controller. The thing holding me back was the non-availability of the media. This would obviously solve that.
Jeff Galinat (proud owner of an Altair clone)

Similar reasons here, so sign me up for one, please Mike. I'd be much obliged!
 

smp

Veteran Member
Joined
Oct 4, 2011
Messages
1,676
Location
Bedford, NH, USA
Hi Mike,

Thanks for another awesomely useful product!

Yes, please put my name on your list for one.

smp
 

deramp5113

Veteran Member
Joined
Mar 9, 2013
Messages
881
Location
Dallas, TX
Now if you can only make one for 8" drives also :)

I actually developed the techniques for making this work reliably while developing soft-sector media support for 8" drives in the Altair FDC+. Unfortunately, the data layout Altair used on their 8" floppy is so tight that soft-sector media just won't work reliably with belt driven drives. However, soft sector media is reliable when used in drives with direct drive hubs like the Pertec FD-400 (typically found in the Altair floppy cabinets) and later half-height 8" drives like the Shugart 810-860 series.

In contrast, the data layouts used on the 5.25" hard sector formats are much more forgiving (about three times as much timing slop allowed), so even belt driven drives seem to work fine with soft sectored media.

I'm not familiar with 8" hard sector formats other than the Altair format. It could be that some other 8" hard sector format allowed more timing slop than the Altair format. If so, these may work fine with belt driven drives and soft sectored media.

Finally, the "rarity ratio" of hard-sector vs soft-sector 8" media isn't nearly as lopsided as it is for 5.25" media. Both media types are almost equally as hard to find in the 8" format, so soft sector media support isn't as big an advantage as it is for the 5.25" drives.

Mike
 

CommodoreZ

Experienced Member
Joined
May 18, 2007
Messages
145
Location
Z Labs.
Out of curiosity, how many components populate this board?

Additionally, any reason that one of these wouldn't work with the hard sectored controller on a Heathkit H89? I realize that it's not an S-100 system, but it isn't all that far off the mark.

This device sounds fascinating nonetheless! I would love to see pictures of the prototypes, if you have 'em.
 

smp

Veteran Member
Joined
Oct 4, 2011
Messages
1,676
Location
Bedford, NH, USA
Additionally, any reason that one of these wouldn't work with the hard sectored controller on a Heathkit H89? I realize that it's not an S-100 system, but it isn't all that far off the mark.

From the way Mike described it, I see no reason that this cannot work with the Heathkit H8 and H89.

smp
 

deramp5113

Veteran Member
Joined
Mar 9, 2013
Messages
881
Location
Dallas, TX
Out of curiosity, how many components populate this board?

Additionally, any reason that one of these wouldn't work with the hard sectored controller on a Heathkit H89? I realize that it's not an S-100 system, but it isn't all that far off the mark.

The board requires just a processor, a transistor, and some diodes and resistors for signal protection.

While I'm not completely familiar with the Heathkit computers, based on the fact that the Heathkit data layout is very similar to the North Star layout, and therefore does not require tighter timing tolerances, this board should work fine with the Heathkit computers.

Mike
 

deramp5113

Veteran Member
Joined
Mar 9, 2013
Messages
881
Location
Dallas, TX
A visit to the SEBHC website shows there is already an adapter that works with the H\Z89.

http://sebhc.lesbird.com/storage/storage.html#HARD_SECTOR_FLOPPY_EMULATOR

Chris did a great job designing the HSFE. In fact, speaking with Chris a while back about the HSFE is what made me add soft sector media support to the Altair FDC+. In the end, Chris was only able to get the HSFE to work reliably with newer 3.5" drives which have a very accurate and steady rotational rate compared to older 5.25" drives.

The primary difference between this newer board and the HSFE is ability to work reliably with the 5.25" drives that are part of the original systems. It does this by syncing to the rotational rate of the current drive and using 24-bit math to prevent cumulative rounding errors when computing each sequential sector time.

I also plan on having a 10/16 sector jumper on the board so it can also be used with 16 hard sector systems like the Altair Minidisk, Micropolis floppy subsystems, and Vector Graphic Micropolis and Tandon configurations.

Finally, I want the new board to not require an external power source. I can achieve this by harvesting power off a few key signals on the ribbon cable. This works great with a typical North Star with Shugart SA-400 configuration. Unfortunately, when different controllers and floppy drives are thrown into the mix, the power-harvesting idea runs into a few hitches - primarily due to different signal terminators (150 ohm pull-up vs 220/330 pull-up/down vs 1K pull-up). At this point, I'm not sure if I'll give up on the no-power idea and build a 9v battery holder onto the back of the board or not.

Mike
 

litterbox99

Experienced Member
Joined
Aug 8, 2010
Messages
103
I would be interested in one board.

I have an Imsai with a NorthStar controller and two iffy SA400 drives.

Drive X only boots/reads certain floppy's , and
Drive Y reads the rest of the floppies...

I want to archive what I have and use modern drives.

Will your product co-exist with a working SA400 ?

I want to strap up a SA400 & your drive converter
to another floppy at the same time so I can archive
off the old media.

What Drives have you tested this with ?.

I do have 20 new hard sectored floppys from Athna,
but I'd rather use a reliable drive that's in alignment.

Todd
 
Last edited:

deramp5113

Veteran Member
Joined
Mar 9, 2013
Messages
881
Location
Dallas, TX
The board is on the drive cable that is common to all drives, so any drive on the cable can be hard or soft at any time.

I have tested with the Shugart SA-400, Tandon TM-100, Micropolis 1015, and Teac 55-GFR. Only the TEAC is a newer direct drive hub. The others are belt driven.

Mike
 

MarsMan2020

Experienced Member
Joined
Dec 19, 2013
Messages
188
Location
Hawthorne, CA
Mike - I'd like 2 boards. Finally got my hands on a Mindless Terminal to go with that MZ you helped me get up and running - it'd be great to be able to use soft sector disks!
 

deramp5113

Veteran Member
Joined
Mar 9, 2013
Messages
881
Location
Dallas, TX
Quick poll,

How many would like to build the board themselves: I provide the board, a programmed processor, and a parts list at Digi-Key. The board would be slightly larger to accommodate thru-hole parts.

Or, the board is completely assembled, tested, and ready to go, a bit smaller, but of course, more expensive.

Mike
 

griffk

Experienced Member
Joined
Jun 4, 2015
Messages
200
Location
Seattle, WA / Los Angeles, CA
Quick poll,

How many would like to build the board themselves: I provide the board, a programmed processor, and a parts list at Digi-Key. The board would be slightly larger to accommodate thru-hole parts.

Or, the board is completely assembled, tested, and ready to go, a bit smaller, but of course, more expensive.

Mike

I say we build them ourselves!

thanks
gwk
 
Top