NeXT MO disks

From: Mark <>
Date: Wed Feb 28 19:25:03 2001


This message replies to several in the thread about NeXT MO disks.

On Mon, 26 Feb 2001 Jerome Fine wrote:
>> A question about MO disks and the Canon MO drive installed in some NeXT
>> cube computers.
>> I know NeXT MO disks are single-sided, commonly quoted as having a capacity
>> of 256MB.
> I have some rather old MO disks as well, but they are made by Sony and are
> for a 5 1/4" Magneto Optical Disk drive - an S501. They are very close to
> 290 MBytes on each side and are formatted for 512 bytes per sector.

The sector layout is stamped into the disk at the factory; it is not possible
to change. That's why there are two variants, e.g. 600MB and 650MB for first-
generation drives. 600MB disks have 512-byte sectors, and 650MB disks have
1024-byte sectors. The extra capacity of 650MB disks is because less space is
wasted on sector headers. Without special driver software, some computers only
work with media with 512-byte sectors, which is why the lower-capacity disks

(On a kind-of-related note: I understand the sector layout or servo tracks of
e.g. Zip disks are written at the factory. Does that mean if you degauss a
Zip disk it is then useless, and cannot be reformatted?)

> I don't know anything about the NeXT hardware, but if the shoe fits, ....
>> ...
> Since 250 MBytes per side is close, they might be the same as the ones I
> have. Mine are 5 1/4" disks and formatted at 512 bytes per sector and hold
> about 295 MBytes on each side for a total of about 590 Mbytes per disk.

The Canon/NeXT disks are not the same as the ISO standard 600/650MB disks
which the Sony drive uses. They may be the same physical shape, but that is

A page on the Sony web site indicates that NeXT drives can use 600/650MB
disks. I'm almost certain that is wrong. (The URL of the page is - scroll down to the
Canon section.)

> In addition, a friend of mine has a large number of these disks which he no
> longer wants. For a nominal charge plus shipping and handling, I am sure
> that they can be made available. The shipping alone (these weigh about 1/2
> lb. EACH) will likely be more than the disks, so I do think it is a good
> deal. On eBay, they often try to get the suckers to pay over $ US 5.00 a
> disk just to start, although sometimes they start at a more reasonable $ US
> 2.00 each. I am in Toronto, so the shipping may be more than you want to
> pay!

Shipping may not be that expensive. A while ago I bought 50 5.25" MO disks,
and shipping within the USA by UPS cost $17 (from memory). The "media mail"
USPS rate is comparable to book rate, but for computer media.

Getting an older MO drive and disks is a really cheap way to get reliable
removable storage. The drives are so cheap (usually under $25 for a 650MB
drive, under $50 for 1.3GB) it is practical to get one for each computer.
Used disks cost $1 or $2 each. Way better than using a Zip drive, I think.

On Mon, 26 Feb 2001 Jeff Hellige wrote:
>> I have some rather old MO disks as well, but they are made by Sony and are
>> for a 5 1/4" Magneto Optical Disk drive - an S501. They are very close to
>> 290 MBytes on each side and are formatted for 512 bytes per sector.
> If I recall correctly, one of the problems with the MO drives
> was that there was little to no standardization of the formats or
> disks for the drives.

That's not really true any more. Well, since 1991 anyway.

Before the original ISO standard was finalised, there were some problems with
interchanging disks between drives from different companies. This was
around 1989-1990. I believe most manufacturers updated the firmware of their
drives to solve the problems.

The major standard 5.25" MO capacities are:
  600/650MB "1x", ISO 10089 Format A
  1.2/1.3GB "2x", ISO 13549
  2.3/2.6GB "4x", ISO 14517
  4.1/4.8/5.2GB "8x", ISO 15286
  8.6/9.1GB "14x", new, no standard published yet

Newer drives can usually read all, and write to some or all previous

Currently 5.25" MO drives are manufactured by Maxoptix and Sony (HP and IBM
drives are manufactured by Sony). They are completely compatible; a Maxoptix
drive can read disks written in a Sony drive etc.

In the past, drives have also been made by at least Ricoh, MOST, NEC, Nikon,
Sharp, Pinnacle Micro, IBM, HP. Disks written on any of those should be
readable on modern drives.

There are some other less common capacities; Hitachi made a drive which used
1.7GB/2GB disks, Pinnacle Micro's Apex drive could use 4.2/4.6GB disks, and
Maxoptix made drives which could use 900MB/1GB disks. All those types of disk
are still available new incidentally, and current Maxoptix drives can read
and write the 900MB/1GB disks.

There are a few uncommon types which you will rarely come across:

 - Pioneer make MO drives which are mainly used in medical imaging
   applications; apparently some CT scanners use Pioneer drives. Drive and
   media prices for these are quite high, as Pioneer are the only source.
   There are three types of rewritable MO media for Pioneer drives: 654MB (ISO
   10089 Format B), 1.7GB and 2.2GB.

 - ... and of course the Canon 500MB disks.

On Tue, 27 Feb 2001 Jeff Hellige wrote:
>> Pinnacle called their drive the REO-650 and in a dual configuration it
>> was called an REO-1300. Since I also have an REO-650 and have
>> looked inside, I can verify that on the early models, this was the actual
>> hardware. Obviously, both the S501 and the REO-650 use the
>> identical media.
> I took a look at the Pinnacle drive today and it is a
> Pinnacle Micro Sierra Optical Hard Drive with a 1.3gig capacity on
> 5-1/4" removable media. Supposedly it is a double-sided cartridge
> capable of holding 650Mb per side. It appears to be a standard SCSI
> drive, but unfortunately I do not have any of the disks for it.

The Sierra is a very nice drive, at least going from the specs; I haven't used
one. Perhaps the fastest 1.3GB MO drive: spins at 4500rpm, average seek time
19ms, 4MB cache memory.

You can use any 1x (600MB, 650MB) or 2x (1.2GB, 1.3GB) MO disks with it. These
can often be found on eBay for a couple of dollars each. 1.2 or 1.3GB disks
will give faster data transfer than 600 or 650MB ones.

-- Mark
Received on Wed Feb 28 2001 - 19:25:03 GMT

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