Have checked the jumpers? Post a photo of the circuit on the back.

POST usually detects drive type HD vs DD and will report an error if you use the wrong type (Floppy Disk Failure). If the BIOS is erroring on 1.2MB then it's a 360K drive really. Is your boot disk HD or DD?

hi I've taken a picture of what I think is the jumper setting on the drive I'm using as requested in messages

jude1977 wrote on 2025-11-16, 11:27:

the drive I'm using is a 1.2mb drive
the floppy I'm using is a dd density disk

DD floppies in 5.25" HD drive kinda work, but not really. The drive should be able to read them but that's it. Writing to DD floppy on HD drive can easily fail, might require multiple attempts and will be long-term unreliable. Unless the floppy is cleaned of the old data first through demagnetization - but even then it's hit or miss (depends on the drive in question) and the resulting floppy quite likely will not be readable in true DD drives.

TLDR: For 5.25" drives at least you need to stick to HD floppies for HD drives, and DD floppies for DD ones. Unless you only care about reading the data.

hi how do i tell if my disk drive is a HD or DD

There are general rules of thumb for 5.25 drives, but they are not gospel.

Generally, low density drives have a red LED, and have a chonkier look/build to them. They tend to be black plastic, or 'glassy/glossy' beige. They tend to have very promiment jumper block headers on the back.

High density drives tend to have green LEDs, and have a more 'clinical' aesthetic to them, with matte textured beige plastic, and a turn down handle. They tend to either omit the schugart jumpers entirely, or conceal them in some fashion.

Again, this is not gospel. Its a generality.

The gospel truth is if it can seek to 80 tracks or not.

Model number would be a good start, but it might not be enough in some cases (conflicting info on the net). Best way to tell is to use software to seek to track 40 to see if that's the end or half-way. End is DD drive, half way is HD.

Most BIOSes do that when "floppy boot seek" option is enabled. The idea behind it is simple, seek to track 42, then count the steps back to zero. On DD drive 42 can't be reached (the head will hit the limiting stop) so going back the count will be less. That way BIOS knows if its DD or HD:
- if drive was set to DD (360K) and count was less than 42 then it's a DD drive indeed, no error
- if drive was set to HD (1.2M) and count was equal to 42 then it's a HD drive indeed, no error
- in any other case report a floppy drive error to screen

You can usually use BIOS mechanism to tell, unless the option is missing or somehow not working right due to other hadrware issues (bad drive, bad cable, etc).

I've found more DD drives to have RED Leds and HD drives to have GREEN (but that's not always reliable)

To tell if a 5.25: drive is DD or HD, best way is by number of tracks (40 on DD, 80 on HD)

Since you are running W98, you can "Restart in MS-DOS mode", then run my ImageDisk tool - it has some fairly comprehensive Test/Analysis tools, which can (among other things) step to any track you want.

Step to track 39 - and look at the drive head position.
If it's noticeably closer to the inside (spindle) end of the disk "access slot" = 40-track = DD
If it's about 1/2 way (closer to center of slot) = 80-track = HD

Btw, if a 5.25" drive is HD and you format it as DD (or read a DD disk) it will "double step" to emulate a 40 track drive.

If however it is set up in the system as a DD drive and for some reason still appears to work - it's won't "double step"

When you format a diskette with it set to a 360k drive, does the head travel the whole length of the "access slot", or does it only go about 1/2 way?

Btw, the reason DD in HD drives isn't always reliable is that the HD head is thinner(supports 80 instead of 40 tracks) - usually not a problem if the DD disk was "new" or bulk-erased and never written on a DD drive ... but if it does get written on DD and then later re-written on HD - the "edges" of the DD tracks still remain, and can confuse DD drives which read with a wider head. Not normally a problem when read on HD.

its all very interesting to know that I will give image disk a try one thing to note it has a red power light and the colour of the drive is a sawt of light brown whitish colour

DaveDDS wrote on 2025-11-18, 13:29:

Btw, the reason DD in HD drives isn't always reliable is that the HD head is thinner(supports 80 instead of 40 tracks) - usually not a problem if the DD disk was "new" or bulk-erased and never written on a DD drive ... but if it does get written on DD and then later re-written on HD - the "edges" of the DD tracks still remain, and can confuse DD drives which read with a wider head. Not normally a problem when read on HD.

Makes me wonder, if the HD heads are able to write double the tracks of a DD drive, why do we double step via a skip? Wouldn't it be better to double step by duplicating the track twice instead? This would result in a more reliable disk for a proper 360K drive.

A few reasons:

1) It might confuse a 360 drive by laying down a track of different data next to each 2nd track : 1 1+ 2 2+ 3 3+ etc...
The 360 would see only 1, 2, 3 ...
But the wider head might see portions of 1+, 2+, 3+...
So take for example 2 - the 360 would see 1+><2><2+ and the 1+ data might be enough to confuse it. (not very likely but more of a risk than a blank track/empty space.

2) Writing takes longer than stepping. You would need to wait at least two revolution (time to step to 1+ would take long enough that it would likely miss it's track lead-in) , possible more depending in interleave.

3) The 2 and 2+ tracks would have to line up EXACTLY ... normally there can be some slight variation in sector offsets from track to track... The FDC syncs to the lead-in on each track it reads, and
"identical" adjacent track might be slightly offset would could cause confusion to the wider head.

4) In the industry, this was almost never a problem - Products manufactured on 360k ... were written in 360k drives and in most cases on new (never written) media.
Generally the common cases of writing on 360 and then 1.2 were users re-using old disks on new drives. and most of these never went back to trying to read the disks on their older drives.
.. and those users who did have and switch between both drive types generally learned of the limitations fairly quickly ...

So... although the chances of making it worse are very low, they are >0 - and if it did make a slight benefit in some cases, it wouldn't be significant, and definitely not worth the reduction in write speed.

that's very interesting to know thanks for informing me that

Btw, the reasonI I say "not very likely" is that the reason 360s rewritten on 1.2s can have trouble is that the edges of the original 360k track can still remain and are therefore bumped up against the new 1.2m track with no gap at all and within the area covered by the 360k head.

Even adjacent 1.2 tracks will have a gap, and much less of the adjacent 1.2 data would fall within the coverage of the 360k head - meaning the actual track would be much stronger when read on 360k.

If only the NEC765 FDC used in the PC had an "erase track" function - then you could erase the adjacent tracks when writing in a 1.2 which might make even less of the original 360k tracks "visible".
- but still not worth the extra time it would take to write to the disk, given that the chances are quite low what it will be read on a 360k again -

It's kinda weird - the whole reason rewriting 360k with 1.2 is a "problem" is that it happens infrequently enough that it's not obvious to someone not "in the know" why "this one disk" has read errors after having done dozens that appear to work fine! (if rewriting a 360k on 1.2 always caused failures - that would have fairly quickly "become a thing" that people knew and understood!