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cfsimmons
July 21st, 2019, 01:24 PM
I made an interesting discovery today. After taking another look at the pinout for the 2.4 meg drive, I decided to see what happened when I pulled pin 2 low while the disk was spinning. The drive went from 360 rpm to 180 rpm, which I confirmed with my scope. Additionally, the read data waveform seemed to change a bit but I can't really quantify this.
Anyway I decided to try imaging the disk in this mode using a pentium machine with the HxC floppy software. With pin 2 jumpered to ground the program successfully read 30 sectors per track with the exception of track 0 side 0 which we had already determined to be formatted normally. In the end I have a 2,441,216 byte image file.
I tried switching the jumper after the program read track 0 side 0 but the program would only read 15 sectors for the subsequent tracks.

I suppose with this knowledge, someone could hack up a better solution for reading and emulating these disks.

edit: I should also mention that I found several EBCDIC strings in the image.

Chuck(G)
July 21st, 2019, 02:34 PM
That pretty much agrees with my suspicion--Weltec, back in the day (ca. 1986) offered a rather unsuccessful drive that allowed the use of 1.2MB floppies on a stock PC-XT by switching the spindle speed from 300 (for 360K media) to 180 (for 1.2M media). It was fabulously unsuccessful, lasting less than a year. The drive was a 96 tpi unit, so it had the usual liabilities of the AT double-stepped 360K floppies, though Weltec did offer software to do single-stepped 360K media. Where it really fell down was reading 1.2M media. Recall that the current induced in a disk read head is proportional to the linear speed of the media. At 180 RPM, it just didn't work well. Weltec dropped the HD media claim and just sold the thing as a 360K/720K unit. Good times.

So the idea isn't dead. Running your drive at 180 RPM should render it compatible with any PC high-density imaging utility. No need for special hardware.

Emulation may be a problem as the track at 2.4MB is twice as long as a standard 1.2MB one; The usual emulation hardware (e.g. Gotek) may not have enough RAM to do the job.

g4ugm
July 22nd, 2019, 12:16 AM
That pretty much agrees with my suspicion--Weltec, back in the day (ca. 1986) offered a rather unsuccessful drive that allowed the use of 1.2MB floppies on a stock PC-XT by switching the spindle speed from 300 (for 360K media) to 180 (for 1.2M media). It was fabulously unsuccessful, lasting less than a year. The drive was a 96 tpi unit, so it had the usual liabilities of the AT double-stepped 360K floppies, though Weltec did offer software to do single-stepped 360K media. Where it really fell down was reading 1.2M media. Recall that the current induced in a disk read head is proportional to the linear speed of the media. At 180 RPM, it just didn't work well. Weltec dropped the HD media claim and just sold the thing as a 360K/720K unit. Good times.

So the idea isn't dead. Running your drive at 180 RPM should render it compatible with any PC high-density imaging utility. No need for special hardware.

Emulation may be a problem as the track at 2.4MB is twice as long as a standard 1.2MB one; The usual emulation hardware (e.g. Gotek) may not have enough RAM to do the job.

what we still don't know is how the drive knows its a 2.44m disk.....

g4ugm
January 3rd, 2020, 02:35 AM
That pretty much agrees with my suspicion--Weltec, back in the day (ca. 1986) offered a rather unsuccessful drive that allowed the use of 1.2MB floppies on a stock PC-XT by switching the spindle speed from 300 (for 360K media) to 180 (for 1.2M media). It was fabulously unsuccessful, lasting less than a year. The drive was a 96 tpi unit, so it had the usual liabilities of the AT double-stepped 360K floppies, though Weltec did offer software to do single-stepped 360K media. Where it really fell down was reading 1.2M media. Recall that the current induced in a disk read head is proportional to the linear speed of the media. At 180 RPM, it just didn't work well. Weltec dropped the HD media claim and just sold the thing as a 360K/720K unit. Good times.

So the idea isn't dead. Running your drive at 180 RPM should render it compatible with any PC high-density imaging utility. No need for special hardware.

Emulation may be a problem as the track at 2.4MB is twice as long as a standard 1.2MB one; The usual emulation hardware (e.g. Gotek) may not have enough RAM to do the job.

There is code to go in a GoTek here:-

https://github.com/9track/FlashFloppy

I have been using it with some success in a couple of my 3174s...

WBST
January 4th, 2020, 07:22 AM
what we still don't know is how the drive knows its a 2.44m disk.....

It's definitely not any physical indication. It must be a test write, seek away, seek back, check what is read is as expected sort of thing, or something similar.

g4ugm
January 4th, 2020, 07:43 AM
It's definitely not any physical indication. It must be a test write, seek away, seek back, check what is read is as expected sort of thing, or something similar.

I was wondering if its a simple marker on the first track...

WBST
January 4th, 2020, 07:58 AM
I was wondering if its a simple marker on the first track...

I checked and there aren't two "sector 0" holes, no visible physical differences in sleeve. It'd be very IBM to do something like the old 720KB/1.44MB drive test. Maybe there's something about the "Vertical Recording" method needed?

Chuck(G)
January 4th, 2020, 08:42 AM
How about "Read ID"? That is, you do what's done on the 5170 BIOS for the 1.2M drives--try a Read ID at one data rate, then the other and adjust accordingly.

g4ugm
January 4th, 2020, 03:22 PM
How about "Read ID"? That is, you do what's done on the 5170 BIOS for the 1.2M drives--try a Read ID at one data rate, then the other and adjust accordingly.

i believe the first track is 1.2 format for both drives, so a marker in the header?

WBST
January 4th, 2020, 03:32 PM
i believe the first track is 1.2 format for both drives, so a marker in the header?

But then what about formatting blank ED diskettes? That'd be all well and good for pre-formatted diskettes though.

Chuck(G)
January 4th, 2020, 04:43 PM
You tell the system what you're using.

You can, for example, try to format an HD 5.25" as 360K or a DD 5.25" as 1.2M; it probably won't succeed, but there's nothing on a 5.25" that indicates the density, so the system will try anyway.

Read ID on track 2 will reveal the density of whatever's in the drive. How do you think that the 5170 BIOS does it?

g4ugm
January 5th, 2020, 11:29 AM
You tell the system what you're using.

You can, for example, try to format an HD 5.25" as 360K or a DD 5.25" as 1.2M; it probably won't succeed, but there's nothing on a 5.25" that indicates the density, so the system will try anyway.

Read ID on track 2 will reveal the density of whatever's in the drive. How do you think that the 5170 BIOS does it?

I don't think there is anything in the 3174 menus that let you format a diskette, full stop.

Chuck(G)
January 5th, 2020, 12:45 PM
My impression was that the 2.4M 5.25" drive was strictly for distributing firmware; hence, read-only. Just pointing out that there's no mechanism to detect the media type without reading already-written data.

g4ugm
January 5th, 2020, 02:43 PM
My impression was that the 2.4M 5.25" drive was strictly for distributing firmware; hence, read-only. Just pointing out that there's no mechanism to detect the media type without reading already-written data.

Chuck,

No, the 3174 will read and write 1.2 and 2.4 diskettes. You need to configure the firmware so it has to write the updated files back to the floppy. You might also want to make backups. If you have a dual floppy system you can copy a floppy to another floppy but they have to be the same format. If you have a hard disk you can copy a floppy to the hard disk where it will create a folder, and copy the content of the disk to the folder. You can also, as I discovered recently also copy the content of a folder on the hard disk back to the floppy disk. You don't get any choice of names so you can only have one "Utilities" , one "Control" and one "Extensions" folder.

There is a feature called "central site customization" which I haven't explored which allows you to build multiple configs on one controller and distribute them remotely either via Netview or via physical floppies so perhaps that lets you have multiple floppy images on the hard disk, but that's one for tomorrow....

Dave

Chuck(G)
January 5th, 2020, 04:23 PM
I remember having a conversation with Herb Johnson about the drives some time ago. I don't recall what was said, only that I didn't find anything startling about the drive, other than bringing pin 2 low resulted in the drive spinning at 180 RPM.

g4ugm
January 6th, 2020, 12:05 AM
I remember having a conversation with Herb Johnson about the drives some time ago. I don't recall what was said, only that I didn't find anything startling about the drive, other than bringing pin 2 low resulted in the drive spinning at 180 RPM.

I wonder if that can be used in some way to detect the drive type?

Chuck(G)
January 6th, 2020, 07:40 AM
I would certainly think so if a disk were inserted. Just time the index pulse interval. Absent a disk in the drive, probably not.