ESDI Magneto Optical Drive

Jerome Fine replies: The first SCSI MO drive I ever used was from Sony. The SMO S-501 consisted of two parts (this is from memory and it was over 15 years ago - so it is likely unreliable): (a) A C-501 PCB about the size of a 5 1/4" drive which had a 50 pin SCSI header interface for the host adapter and a 34 pin / 20 pin (2 of these if I remember correctly) header interface for each of the 2 supported drives. This board was called a controller and was completely separate (b) A D-501 5 1/4" drive which I was told had a MODIFIED ESDI interface and used standard 34 pin / 20 pin edge connectors. Exactly what the word modified meant specifically was never made clear, however, Sony made it VERY clear that the C-501 controller PCB was required to interface the D-501 drive to a SCSI host adapter and any warranty on the D-501 drive seemed to be dependent on using the C-501 controller as an interface. In practice, the C-501 actually handled TWO D-501 drives, so the complete set up was a bit less expensive than later drives for which the 50 pin controller interface was embedded with the drive - when TWO drives were used. Since the customer who ordered the dual MO drive setup used a SCSI host adapter as the interface - and no other interface was available at the time, the question of using the C-501 never arose. It sounds like you are being sold a D-501 drive without the C-501 controller. Eventually, the C-501 / D-501 was discontinued and Sony produced ONLY an integrated SMO S-501 drive. By the way, the capacity of each SMO S-501 drive or the original D-501 was 295 MB using a 512 byte sector size. MOST media were double sided, although that meant physically removing the media, turning the media over and inserting it back into the drive. Which meant that ONLY one side could be used at a time. However, someone in marketing decided that the SMO S-501 had a 590 MB capacity and the drive was advertised and sold on that basis. Sort of like the original 180 KB byte floppy drive and single sided media - which could have additional holes punched and the other side used as well. BUT I never heard of a 180 KB 5 1/4" floppy call a 360 KB drive when used with media that could be removed and turned over, then inserted again to use the other side. Over the past decade, the SMO S-501 drives with the embedded controllers have been available on eBay and sold for less than the shipping cost. After I acquired 3 or 4, as well as sufficient media, I used them as my primary backup on the PDP-11/73 for about 5 years in addition to the interchange media for the Pentium III running RT-11 under E11 using, yep, the same SMO S-501 drive (with an Adaptec AHA-2940AU host adapter). The drives don't receive much use lately since the backup has become 4.7 GB DVD media on the Pentium III, although if I ever need to transfer anything over 10 MB back to the PDP-11/73, I guess that the SMO S-501 would be the drive to be used. Does this answer your question? If you need some media, I can probably make some available. But I would suggest that you pass on the D-501 drive and get the SMO S-501 if you really want to use that type of media. If the vendor is willing to loan you the drive to test it (at his risk) on your ESDI controller, then I guess that might be reasonable if you enjoy the challenge. Sincerely yours, Jerome Fine -- If you attempted to send a reply and the original e-mail address has been discontinued due a high volume of junk e-mail, then the semi-permanent e-mail address can be obtained by replacing the four characters preceding the 'at' with the four digits of the current year.