• Please review our updated Terms and Rules here

Adding a 3.5" Drive to a 5150

tempest

tempest

Veteran Member
Joined
Sep 16, 2014
Messages
930
Location
SE Michigan
My IBM 5150 (with the 3rd BIOS revision) currently has two half height 5.25" drives and a full height hard drive in the other bay. While two 5.25" drives are nice, I'd much rather replace one of them with a 720K 3.5" drive. I have three questions about this:

1. Can I just stick any old 3.5" drive in the 5150 or does it need to be a specific kind of 3.5" drive?

2. Can I use the same floppy cable the 5.25" drive used? I think my cable has 3.5" connectors but I'm not sure.

3. Since 3.5" drives are smaller than a 5.25" drive, how do I fit it in? I've seen some pictures where the 3.5" drive has a nice plastic bezel around it, but I'm not sure how to find one of these or what they're even called (is it just a bezel or some kind of sled as well?).
 
Any old 3.5" drive will work as 720K. There's an adapter you can get which is basically mounting rails and a plastic bezel. They're most commonly white or beige, and a cheap trick to make them black is to go get a can of vinyl dye spray and spray the faceplate. Unlike paint, vinyl dye soaks into the plastic and changes the color, so it won't chip off over time.

As long as your cable has the correct connector, you should be fine. There were adapters to go from the card edge connector to a dual-row pin connector.

You can also get floppy controllers that will allow the drive to function as a 1.44 MB drive -- they have their own controller and BIOS, and replace the default IBM controller.
 
You need a mounting kit:

http://www.ebay.com/itm/182118392378

A kit like that includes everything you need (hardware-wise) to install a standard 3.5" floppy drive into an IBM 5150 PC, except for the brackets to mount two half-height drives into one of the full-height bays (but copious amounts of duct tape will also take care of that :) ). You can use it with any standard PC/XT floppy drive controller, and it will operate in 720K compatibility mode, so you can read and write 720K Double Density disks, but not 1.44 MB High Density disks.

If the rest of your drives are black and you want to match the color, you can also find the mounting frame (and of course the 3.5" floppy drive itself) with a black faceplate, however, in that case you'll probably need to buy the power and data cable adapters separately, as only the beige mounting kits seem to come bundled with them.
 
Don't forget to remove/disable the termination on the 5.25" drive if you choose to make the 3.5" the A: drive.
 
krebizfan said:
Don't forget to remove/disable the termination on the 5.25" drive if you choose to make the 3.5" the A: drive.
Click to expand...

I've previously read other posts suggesting to remove/disable the termination on the 5.25" drive if you choose to make the 3.5" the A: drive

I have a 5160, with a high-density controller, and my 3.5" floppy is a 1.44MB A: drive and my 5.25" 1.2M floppy is my B: drive. They seem to operate OK except when I added a CF C: and D: drive via an XT-IDE adapter. When the 5.25" 1.2M B: drive is connected, the directories CF C: drive gets corrupted intermittently when written to. When I disconnect the 5.25" drive the CF C: drive doesn't get corrupted. The theory is that even though I think the BIOS of the FC isn't conflicting with the BIOS of the XT-IDE, we're not 100% certain, so I'm about to try a new XT-IDE that packs both the HD floppy BIOS into the same EPROM and the XT-IDE BIOS to eliminate that possibility (I'll do that anyway 'cause it will also allow be to lose the FDC, use a 16-bit multi-function adapter with non-BIOS FDC connector and thus free up a slot). I'm not sure if that will fix the CF C: drive from getting corrupted when the 5.25" 1.2M C: drive is connected - I've been wondering if maybe the corruption might have something to do with the termination you mention, but when I've looked at the rear of the 5.25" drive I have no idea how I'd disable the terminator. The drive is a Teac FD-55GFR, and it has jumpers listed here ( https://groups.google.com/forum/#!msg/comp.sys.ibm.pc.hardware.storage/U-2bPTdJZOc/ogjLfUcqYRAJ ) but I didn't see anything that referenced a terminator. What exactly happens if that isn't done? I've read that it is a good idea to remove a terminator on a floppy drive not at the end of a cable to 'not muffle the signal' - so I am really confused over what to look for re: floppy drive termination via jumper or chip.

Regards,
Mike
 
Last edited:
Don't sweat the terminator if it's not removeable (sometimes appears as a DIP or SIP in a socket).

Older 8" and 5.25' drives used a 150 ohm pullup, which was fine for long (>1m) cables, but completely overkill for the short distances used in the PC. The point was to reduce the possibility of line reflections by terminating both ends of a floppy cable. When two of the old drives with 150 ohm terminators were used, one had to be removed simply because driving a 75 ohm-to-Vcc load requires more power than the driver (7438) is rated for.

But later 3.5" and 5.25' drives simply use a large (>1Kohm) terminator and it doesn't matter if both drives have them connected or not.
 
Chuck(G) said:
Don't sweat the terminator if it's not removeable (sometimes appears as a DIP or SIP in a socket).

Older 8" and 5.25' drives used a 150 ohm pullup, which was fine for long (>1m) cables, but completely overkill for the short distances used in the PC. The point was to reduce the possibility of line reflections by terminating both ends of a floppy cable. When two of the old drives with 150 ohm terminators were used, one had to be removed simply because driving a 75 ohm-to-Vcc load requires more power than the driver (7438) is rated for.

But later 3.5" and 5.25' drives simply use a large (>1Kohm) terminator and it doesn't matter if both drives have them connected or not.
Click to expand...

Thanks for clarifying that!

Mike
 
I just looked, my cable only has 5.25" drive connectors on it (I think it's original). I'll have to find a cable with both on them, hopefully that won't be difficult.
 
hello
a bit related to the subject.. i like the idea of "clean" old floppy controler and a somewhat new 720kb read/write function.
But, when trying to read/write the 720kb , personally i have not made any connection to windows 7 usb flopyy to a 720kb disk. Perhaps i did buy a usb-floppy to cheap ??
Anyhow today , i tried this out and it works :)

Disassemble an old cdrom-writer usb drive. Mount a 120mb LS floppy drive (with IDE interface) instead of the cdrom-drive .


View attachment 31379

i was able to read + write + (in CMD) format a:
...have not tried installing software that are copyprocted , perhaps it kind of not function ??

PS in windows 7 the drive appears as "matshita ls-120 ver5 00 usb Device"
/cimonvg
 
The problem with USB and PATA floppy drives is that they're first cousins to SCSI floppies; that is, they're relative-sector addressed and assume a pre-selected layout. So, they'll do MFM 512x9x2x80, 512x18x2x80 formats--and in some cases, do 1024x8x2x80, but that's it--and it's "normal" sector headers. If you have an unusual ID address header, or a sector that's not 512 bytes, or more than 9 or 18 sectors, it won't understand.

AFAIK, it's been that way since the very first USB floppy drives.
 
You must log in or register to reply here.
Back
Top