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Exidy Sorcerer disk drives

Michanek

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Jan 25, 2022
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I'm looking for valid information (not guesses) on what brands and models of disk drives that could be used with the Exidy Sorcerer computer.
I know there was an S-100 expansion box for this computer, to which you could connect disk drives. But I also know that there were disk drives that could be connected directly to the 50-pin expansion bus at the back of the computer, without any need for an expansion box. It is such disk drives I'm looking for.
Could the Micropolis model 1042 (see image) be such a disk drive, or did it need more hardware to be used with the Sorcerer?

I have found an Exidy manual for "Floppy Disk Subsystem", which contains the following info:

1.3 Configuration. You can use your Floppy Disk Subsystem in two configurations:
1.3.1 One stand-alone unit. This uses a 50-conductor cable (supplied) from the Sorcerer to the unit and an AC power cord. The cord is supplied with the unit, but not attached to it.
1.3.2 One unit plus an add-on. There are two cables, a 34-pin flat cable and a 4-conductor power cable. These two run between the main unit and the add-on.

2.4 Floppy Disk Subsystem Add-on. You may purchase from your Exidy dealer or distributor an optional add-on disk drive unit.
This unit comes with a 34-conductor cable and a power cord. The add-on receives DC power from the main unit and does not require voltage adjustment (as explained in 2.3.1).
Attaching the add-on unit requires removing the cases of both units. You should have your dealer do this for you.

However, it's not clear to me what the "add-on" unit really is.
Is the Micropolis model 1042 a standalone unit or an add-on unit, does anyone know?
 

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Reading the manual again (section 2.4), the only interpretation is that section 1.3.2 refers to two disk drives, one "main unit" (which has the 50-conductor cable) and one "add-on unit" (which has the 34-pin cable).
I think the Micropolis 1042 drive is an "add-on unit" and therefore needs a "main unit" disk drive.
Can anyone confirm this?
 
The $64k question is “does the Exidy Sorcerer contain a floppy controller card to use the drive or not”. From what I remember not.

If the “disk” is plugged into the 50 pin expansion connector, then the floppy disk controller has to be external (i.e. within the disk unit itself).

In this case you would have a “master” disk unit (containing the disk controller and the first disk drive - assuming a single drive - and a power supply) and any “expansion” disk unit would just contain a disk drive and a power supply.

Dave
 
I assume you mean this http://www.bitsavers.org/pdf/exidy/Exidy_Sorcerer_FDS_Operators_Manual.pdf?

The 6400 unit interfaces to the Exidy computer via the 50 pin expansion connector. It contains a disk drive, a power supply and a floppy disk controller (including firmware) that replaces a small amount of RAM in a 48K machine with ROM.

You need one (1) of these units connected to the Exidy.

You can then add a 6402 unit to the 6400 to expand the number of disk drives from one (1) to two (2). The expansion unit (6402) doesn't contain a floppy disk controller and interfaces to the 6400 via a 34-pin ribbon cable.

It also looks like the 6400 provides the low voltage power supplies to the expansion disk unit.

Because the 6400 provides the power supply to the 6402 - there will be a maximum number of expansion disk drives that can be added without an external power supply.

My 'guess' would be that the expansion unit (6402) is just a disk drive unit in a case with a cable.

The Micropolis unit on ebay looks like a bare drive with a power supply and a 34-pin disk cable. If you purchase that, you will not have a floppy disk controller to drive it.

Dave
 
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It also looks like the 6400 provides the low voltage power supplies to the expansion disk unit.

Because the 6400 provides the power supply to the 6402 - there will be a maximum number of expansion disk drives that can be added without an external power supply.

My 'guess' would be that the expansion unit (6402) is just a disk drive unit in a case with a cable.

The Micropolis unit on ebay looks like a bare drive with a power supply and a 34-pin disk cable. If you purchase that, you will not have a floppy disk controller to drive it.

Dave
The expansion units also have their own linear power supply but otherwise all correct 🥰
 
The manual I linked to back in post #4 (page 3 section 1.3.2) implies that there is also a unit that doesn’t contain a mains power supply, but just a disk unit. However, the rest of the manual describes a mains power supply unit within both the 6400 and 6402.

It is just possible there were both types of expansion disk available at one time? This would have made the expansion unit cheaper...

Dave
 
The OP's photo is of a blue-cased Micropolis drive typically associated with the hard-sector S-100 system. In that context what makes the drive an "add-on" is that it doesn't come with the S-100 controller card, manual and CP/M on disk, but once you have those things you can add-on the self-powered second drive. The manual being quoted is for the soft-sector ExidyFDS in which the main drive has an internal controller card in the base of the enclosure. That card does have two 4-pin power outlets on the PCB so could in theory be jumpered to a second drive with no internal PSU. I have never seen such a product. I have not seen a part number for such a DC jumper cable but I have seen the daisy chain data cabled advertised. I think it is more likely in the case of the soft-sector Exidy FDS that the documentation writers described the configuration that the engineers allowed provision for but management decided all drives would be self-powered. Maybe for power budget reasons (these drives use a leadscrew to move the head) or because it justified a higher price. However none of that proves that the configuration you describe never existed.
 
Greetings all,

I am an experienced Sorcerer user from back in the day. I still have an Exidy system that is working-ish, and am in the process of troubleshooting it and bringing it back to full functionality. Some additional background on my experience: Myself and two other users took over publishing the Sorcerer's Apprentice for a while at its end of life. I have loaded and built the Exidy floppy disc controllers from bare boards and assembled disk drive systems for other Exidy users, but this was after Exidy had stopped supporting the computer system. I will review some of the documentation and hardware that I have and make a more detailed report in a few days. Here are a few things that I can accurately report now.

I confirm what daver2 has reported:

The Exidy Sorcerer did not have a disk drive controller. The stand alone disk drive unit, was an enclosure with a floppy disk controller in the bottom of the case and a disk drive sitting above that. It also had it's own power supply and thus it's own AC power cord. The 50 pin ribbon cable connected the Exidy expansion bus to the disk drive controller. The disk drive controller had connections for two disk drives, both power connectors and 34 pin ribbon cable connectors. The power supply in the 6400 was capable to provide power for two disk drives. I say this because in the aftermarket years the form factor of disk drives became 1/2 the height of the original drives and I ended up packaging two disk drives in the 6400 case for my own system.

Additionally and very importantly the original disk drives used for the Exidy FDS were Micropolis, not sure of the model number, but they were 100 TPI (tracks per inch). This was based on the mechanism of the disk drives from Micropolis and was fixed by the hardware of the drive. In later years these drives became unavailable. Other disk drive manufacturers chose 96 TPI and it became the industry standard. These drives were completely incompatible with 100 TPI formatted diskettes. They look the same but they would not read a diskette that had been formatted on a 100 TPI drive. Since 100 TPI drives were no longer being produced and were increasingly harder to find, many of us chose to buy 96 TPI replacement drives and copy our data over to diskettes that were 96 TPI formatted. This is somewhat confusing, I know, but I thought it would be useful information to include.

Best wishes to all,

Ed
 
Thanks Dave, I'm from the USA, in Arkansas.

Michanek, I am doing a little more research on the Micropolis model numbers that would have been compatible and will post more when I narrow it down. The drives used MFM technology, were 100 TPI, 77 Track Double Sided Drives.

1645296793488.jpeg
 
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About the add-on drive; the one I owned did not have it's own power supply. It had a separate power plug coming from the main drive, powering the add-on drive (DP6401). It came with the FDS Operators Manual that was linked to a few posts up (the version from bitsavers was scanned by me).

The DP6402 was not an add-on, it was the base unit but with a 77 Tracks 100 TPI drive. My guess is that the types were:
  • DP6400 Main unit, 40 Tracks, 48 TPI
  • DP6401 Add-on, 40 Tracks, 48 TPI
  • DP6402 Main unit, 77 Tracks, 100 TPI
  • DP6403 (or DP6401-2?) Add-on, 77 Tracks, 100 TPI
The DP6403/DP6401-2 is really a guess, the others I'm quite confident are correct.

The pictures of the dual drive setup in this post also make it clear that the add-on drive did not have it's own power supply.

Some pictures of the DP6401 drive connected, the serial number label and the connectors on the rear of the drive enclosure:

IMG_0161.JPGIMG_0163.JPGDP6402 rear.jpg
 
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In terms of floppy disk solutions I have seen 3 variants:
  • S100 extension fitted with a disk controller card (either soft sectored or hard sectored). I believe that initially this was the only way to connect a floppy drive to a Sorcerer. I remember reading that there were some reliability issues with this setup that were fixed in the Sorcerer 2.
  • The FDS Floppy Disk Subsystem, which came later and is mentioned in this thread.
  • An integrated floppy disk drive and monitor solution. This also came with it’s own disk controller interface, but I don’t know if it was the same one as in the FDS. Iirc it was also a soft sectored interface.
4E9C4B5E-D19E-455F-9D18-DE7948EDFDA3.jpeg
 
.An integrated floppy disk drive and monitor solution. This also came with it’s own disk controller interface, but I don’t know if it was the same one as in the FDS. Iirc it was also a soft sectored interface.

The PCB number on the controller in the Video Disk Unit that Al Kossow had matches that in my FDS so in that sense I think the two systems were provisioned with the same board. I think we confirmed that the ROMs were the same as well. However I have a manual for a soft-sector controller board with a somewhat different component layout - maybe an earlier revision (if it ever made it market).
 
That is the best pic of the combo monitor/drives I've seen yet. Most are dark and you can hardly see the front of the unit. Always wanted one of those for my Sorcerers. Instead I have the S-100 expansion box and 2 Shugart 801 drives.
 
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