Running an external 2.88 MByte floppy drive under PC/MS-DOS
The hidden CompatiCard IV
I couldn't believe it at first. I bought a Megamate 2.8MB external floppy disk drive on eBay US (about 90 EUR/100 $). It was delivered and lay around for 4 weeks because I had no time. But now, I unpack it and can't believe my eyes! Next to the floppy drive there is a brand new CompatiCard IV as floppy controller.
A CompatiCard IV is currently not traded below 400 EUR on eBay and I paid 90 EUR/100 $ for it. In addition there are 2x 30 EUR for postage and customs.
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Setting up the Megamate 2.8 is very easy. It doesn't take more than 10 minutes. I now have four drives in my 386DX-AT. If I had set up the CompatiCard IV as the second controller, I would even have six drives. But who needs such a thing?
But now to Megamate 2.8. Once set up it reads and writes 720 KB, 1.44 MB and 2.88 MB without problems. The case feels really good; the Megamate 2.8 also 'sounds' really good when accessed. No rattling or anything else. Good workmanship.
Basically there is not much to say about the Megamate 2.8. It does exactly what it is supposed to do.
Basically the Megamate 2.8 can process three formats: 720 KByte, 1.4 MByte and 2.8 MByte. The first two are the classic 3.5 inch floppy disk formats known from MS/PC-DOS computers. New is the 2.8 MByte format.
But watch out! The 2.8 MByte format of the CompatiCard IV is not the official MS-DOS standard format. According to the User's Guide 'is this format unique to CC4DRV and will not be readable with other software packages. These formats were included for people who wish to use the full capacity of the drive'. I can't test this because I don't have another 2.8 MByte drive. The official media descriptor (MD) for the ED format is F0h. The Megamate 2.8 MD is FFh!
Attention when formatting floppy disks! The Megamate 2.8 is 'blind' to the density indicator when formatting. You must make sure that the diskette type (DD, HD, ED) and format type match. Basically you can format a DD (720) diskette in ED (2.8) format with the Megamate 2.8. No error message will be issued. I tried it out. You can then also easily copy a total of 2.8 MBytes of data to a disk formatted in this way. But how long the data can actually be read is questionable. It is not for nothing that the magnetic data carriers have different coating materials and different thicknesses.
According to Chuck(G) and Al Kossow from VCF, HD disks can be written with so-called perpendicular recording, but they are not so stable in the long run because the surface coating is too thin and the cobalt material is not optimal. The barium coating of the ED diskettes is thicker and optimized for perpendicular recording.
ED disks are currently (05/2019) available on eBay for 10 EUR each! What profiteering. So as long as you just want to copy files, the simple HD floppy disks are sufficient. This fact was unknown to me until then. Saved money again!
- Megamate 2.8 user's guide (20 MByte)