Need some help with floppy media

Hello all!

I didn't really get into computers until 1995 or so, so my memory as it pertains to earlier machines is not that great. Wanted to get some clarification from you guys if I could.

I bought an IBM 5150 off craigslist last year. Awesome condition, fully functional.. with keyboard, monitor and printer. The guy I bought it from obtained it after his father passed away. I happily purchased it for $50 and promised the guy that I would save some data off it before I formatted the hard drive. So that's what I want to do.

I recently purchased a Compaq Prolinea 4/25s which is a 486-25mhz machine. it has both the 5.25" and 3.5" floppy drives. What I am trying to determine is what types of media will be supported in these drives. I'm assuming the 3.5 is a 760k drive. I have heard that I can use 1.44MB disks if formatted using 'format a: /F:760'. I've also heard that I will have to cover one of the holes on the disk so it is recognized correctly. Would love clarification on that.

As for the 5.25" drive.. I don't really recall ever using them (except very early in my computer days.. say 1990 or so) so I could use some direction there. Bottom line is I'd like to purchase some media.. not only to transfer the data for the original owner of the 5150, but also so I can transfer games from the 486 to 5.25 media so I can get them to the 5150. I just need to know what I will need to get this done. Would appreciate specifics.. all the different types (double-sided.. HD.. ) are pretty confusing to me. I was never much of a media person

Greatly appreciated!
Kirk

Kirk,

Here are the basic floppy drive types that you will find in a PC compatible:

• 5.25" double density (360KB total)
• 5.25" high density (1.2MB total)
• 3.5" double density (720KB total)
• 3.5" high density (1.44MB total)

The "density" difference refers to the recording media. Double density is quite different than high density. If a drive is designed for both you can read and write both reliably. If a drive is only designed for double density, then it can not read or write high density reliably.

The media determines how much magnetic force it takes to write an imprint, and in turn determines what the maximum amount of storage the medium can hold will be. That is different than the 'format', which is an abstraction. For example, you can take a diskette rated at 1.44MB total and format it to only use 720KB. But you can't format a diskette rated for 720KB total and format it much higher than that, because the media just isn't designed to handle the requirements for adding that much data.

Take a look at http://brutman.com/PCjr/diskette_handling.html for the details.

In your case the Compaq should have modern drives that support both double density and high density media. ie: That is a 1.2MB and a 1.44MB drive in there. The PC5150 uses only double density media, unless somebody has altered the drive controller.


Mike

There are two basic types of 5 1/4" media - High Density (HD) and Double Density (DD). You need DD.

Double Density 5 1/4" media holds 360k. It was what was around when the 5150 came out. High Density drives didn't appear until the PC/AT. HD media holds 1.2mb. The disk media is very different though - you CAN'T use HD media as DD or vice versa. It works OK on 3 1/2" floppies, because the media there is pretty similar, but on 5 1/4" floppies, it doesn't work at all.

A 486 should definitley have a HD 3 1/2" drive, as well as a HD 5 1/4" drive.

Use DD 5 1/4" floppies for transferring data to the 5150. For best results, format them in the 5150, then write to them with the HD drive, then move them back to the 5150 and copy the data (using the 5150's drives) to a fresh disk. The HD drive writes narrower tracks, since it has a narrower 80 track head, and mixing and matching writes between drives will cause problems.

You know, a while ago, I wrote a whole long article about the differences between floppy disk media, intending to post it here, but never did. Maybe I need to

-Ian

Awesome, guys! Thanks for all the useful info. Looks like I'll be doing some reading tonight.

abigbadzebra said:

Awesome, guys! Thanks for all the useful info. Looks like I'll be doing some reading tonight.

Click to expand...

Something that is not always clear in these discussions: "High Density" drives are usually (but not always) really Dual-Density drives, i.e. they are capable of operating in either High- or Double-density mode, normally selected by the controller on pin 2 of the interface or by the HD media select hole in a 3.5" disk.

The type of diskette to use depends on the selected format and not necessarily the drive type; it's not quite as critical in 3.5" drives, but in general you should only use HD diskettes in an HD drive in HD (1.2 or 1.44MB) mode, and use DD diskettes in DD drives and HD drives in DD (360/720K) mode.

MikeS said:

Something that is not always clear in these discussions: "High Density" drives are really Dual-Density drives,.

Click to expand...

Not always, Mike! It's something for purchasers to be aware of. Before there were dual-mode 5¼" drives, there were high-density 5¼" drives--mostly Japanese manufacture. There's no density select and no "Disk Changed" line (just a "Ready" line). Quite often these also have head-load solenoids.

They don't work at all at DD/250K speeds. If you need some elaboration, I can post a photo of one.

With floppies getting rarer, there's always the chance that someone is going to try and pass one of these off as a dual-mode drive.

Chuck(G) said:

Not always, Mike! It's something for purchasers to be aware of. Before there were dual-mode 5¼" drives, there were high-density 5¼" drives--mostly Japanese manufacture.

Click to expand...

Point taken, thanks, and appropriately edited. Of course most drives these days are going to be PC/AT compatible but you're right, you never know.

And then there are the odd Sonys, three-density drives, the in-between Quad Density drives, non-standard interfaces etc... ;-)

I really just wanted to clarify that when using a dual-mode drive the type of disk should match the mode (format) and not the drive type.

Bottom line: check the model number (and double-check; lots of misinformation out there on the 'web) and use the appropriate diskettes.