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Was there a 720K 5.25" disk format?
- Thread starter alank2
- Start date
krebizfan
Veteran Member
The so called quad density drives provided 720kB formats. Very common with Sanyo systems.
Chuck(G)
25k Member
640K, 720K and 800K were common 96 tpi formats. But several 8088 machines had that option (e.g. Sanyo MBC-555-3, Eagle 1600).
The Olympia people used 96 tpi disks, but used only 8 sectors per track, for 640K. The DEC Rainbow used 96 tpi drives, but were only single-sided, but 10 sectors per track for 400K.
The Olympia people used 96 tpi disks, but used only 8 sectors per track, for 640K. The DEC Rainbow used 96 tpi drives, but were only single-sided, but 10 sectors per track for 400K.
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Chuck(G)
25k Member
I think there might still be a program of mine on early SIMTEL20 called "AT720" or some such (too long ago) that supported the 720K format on the AT 1.2MB drive.
SomeGuy
Veteran Member
IBM never officially supported any 5.25" 720k or similar 96TPI low density format. As a result most clones also did not officially support that.
There were a few programs that could format such disks on a standard IBM PC and use them as long as a bios patch program was loaded.
I used to have most of my low density "360k" disks formatted ~830k using 10 sectors of 512 bytes per track and a few extra tracks. Interestingly, even most single-sided single-density disks, usually rated for ~96k could handle that 830k format. That was a huge increase in capacity.
The Eagle 1600 was an odd exception as it used 1024 byte sectors.
The Tandy 2000 also used 5.25" quad density drives. If I recall correctly its 720k format was the same as 3.5" 720k.
There were a few programs that could format such disks on a standard IBM PC and use them as long as a bios patch program was loaded.
I used to have most of my low density "360k" disks formatted ~830k using 10 sectors of 512 bytes per track and a few extra tracks. Interestingly, even most single-sided single-density disks, usually rated for ~96k could handle that 830k format. That was a huge increase in capacity.
The Eagle 1600 was an odd exception as it used 1024 byte sectors.
The Tandy 2000 also used 5.25" quad density drives. If I recall correctly its 720k format was the same as 3.5" 720k.
eeguru
Veteran Member
AT&T 3B2s also used 720K 96tpi
A couple of my Z80 machines had them. I've made sure to collect spares, they're not too common.
Eagle did a semi-clever thing with the IIE. They sold it with either 360k or 720k drives. To make the boot disks compatible, the double-sided one had the same track layout, only switching to side 2 at track 41. We changed the bios on ours to switch sides for each track, and reoptimized the interleave, which speeded things up nicely.
Eagle did a semi-clever thing with the IIE. They sold it with either 360k or 720k drives. To make the boot disks compatible, the double-sided one had the same track layout, only switching to side 2 at track 41. We changed the bios on ours to switch sides for each track, and reoptimized the interleave, which speeded things up nicely.
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Chuck(G)
25k Member
There were a lot of CP/M systems that used them.
The 100 TPI 77 track 5.25" floppies are worth a mention in that vein.
The 100 TPI 77 track 5.25" floppies are worth a mention in that vein.
tipc
Banned
I seem to recall Winimaging Tandy 2000 disks in a hd drive with Windows 2000 Server.
You can tell your system that your 5.25" HD drive is a 3.5" DD drive, and you'll get a 720K format as well.
tipc
Banned
5 1/4" "quads" won't necessarily work in a vanilla pc though. The Tandy 2000s Mitsubishi 4853-1 floppy drives will not work in a Tandy 1000, this I know. Some more or less standard IBM workalikes used dd drives that wouldn't work in a standard clone either. The Leading Edge model m comes to mind. The TIPC, though not a true IBM compatible, also used non standard Epson drives link.
This is way off-topic. As long as the floppy drive is installed and is working within its current PC and is 96 TPI capable the 800.COM TSR I attached here and several others like 2M will make transparent the usage of additional 720/800K formats.
Stone
10k Member
The 2M-XBIOS is great. I'm using it with a 1.44M floppy on my XT. It's great being able to use 1.44M disks without any special hardware.
Chuck(G)
25k Member
Do you mean other than a 3.5" drive and a controller capable of 500Kbps?
Trixter
Veteran Member
AT&T 6300s (ie. Olivetti M24 and rebadges) had this as a DIP switch option. It came disabled for obvious PC compatibility reasons.
Stone
10k Member
Of course... are you a mindreader?
1ST1
Veteran Member
Yes, right, but officially it was sold as 640 kB (8 sectors) drive, but no problem with 9 sectors. I have two of these Toshiba drives at home, very special ones, with a central flap to close, and a switch to lock that flap, you can see one of them in the M21 with BIOS 1.44 which recently was sold (to the US, through a helper in Italy). I am planning to rebuild one of my M24 with these drives.