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Monster FDC - Dual-FDC floppy disk controller card supporting 8 floppy drives

sergey

sergey

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Silicon Forest, Oregon, USA
Hi,

A few people recently asked about connecting more than 2 drives to their PCs... So here is my answer - Monster FDC controller.
(Of course one could install a second FDC card, but what is the fun in this?! Also there are not many cards out there that can be configured as a secondary FDC)

The card is fairly flexible. It can have up to two Intel 82077 or National Semiconductor PC8477B. One is hardwired as a primary FDC - I/O base address 0x3F0, IRQ6, DMA channel 2), another is configured as a secondary FDC - I/O base address 0x370, IRQ and DMA are configurable. It appears that two FDCs can share an IRQ and DMA, by disabling IRQ/DMA using bit 3 of the FDC Digital Output Register (DOR) while the FDC is not active. Of course either one of FDCs is optional.
The card also includes a socket for the BIOS extension ROM that supports either 32-pin Flash ROM devices or 28-pin EEPROMs, and a serial port, which has configurable I/O base and IRQ.

The current design files are here: https://github.com/skiselev/monster-fdc

The design is mostly done, and I am interested to hear any feedback.
  • Would you be interested in something like this?
  • Should I offer fully assembled cards? a kit? PCBs only? All of the above? ;)
Some intentional design choices:
  • No external FDC connector - It is not difficult to make a 34 pin header to DC-37 connector cable using IDC connectors and a piece of a ribbon cable
  • No card edge FDC connector - again, a matter of making cables. There are plenty of pin header style cables out there...
  • Jumpers instead of switches.... they make IRQ selection more fun, and also more visible ;)
Thanks,
Sergey
 

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Nice work, Sergey! As noted elsewhere, I've taken to routing a single-drive supporting motherboard to a switch-selected DC-37 on a bracket. There are a lot of later motherboards with FDC support, but only a single drive. My prototype is wire-wrap, but a PCB might be nice for some folks. Perhaps even for an internal alternate drive? After all, ISA motherboards are getting hard to come by.

Selectable port, IRQ and DMA allow one, with the right software, to run controllers concurrently. We had a product called SyDupe that did this quite well.
 
sergey said:
  • Would you be interested in something like this?
Click to expand...

Does it support reading, writing and formatting single density? That is a major plus when dealing with vintage formats?

Does it support 5 1/4" 1.2 MByte format? If so, added connectors to plug in cables for 8" drives is also a plus for some.
 
No external FDC connector - It is not difficult to make a 34 pin header to DC-37 connector cable using IDC connectors and a piece of a ribbon cable
Click to expand...
No it's certainly not difficult, but it does consume a slot. Would be more useful than a serial port that almost every ISA PC already has.

Otherwise I love it
 
BillGee said:
Does it support reading, writing and formatting single density? That is a major plus when dealing with vintage formats?

Does it support 5 1/4" 1.2 MByte format? If so, added connectors to plug in cables for 8" drives is also a plus for some.
Click to expand...

Given the FDC chips (National 8477), the answer to single-density is "yes". The Intel 82077, not so much. Likewise, for 1.2M 5.25" 300Kbps, the answer is "yes".
 
I think it looks great! I would buy one for sure.
 
maxtherabbit said:
No it's certainly not difficult, but it does consume a slot. Would be more useful than a serial port that almost every ISA PC already has.

Otherwise I love it
Click to expand...

Disagree strongly. COM port on FDC is a huge bonus. LPT is often on video card (MDA, Hercules, some CGA and EGA). So getting one COM port on FDC is avesome, especially on 5 slot systems.
 
Chuck(G) said:
Given the FDC chips (National 8477), the answer to single-density is "yes". The Intel 82077, not so much. Likewise, for 1.2M 5.25" 300Kbps, the answer is "yes".
Click to expand...

Not necessarily.

The NEC 765 supports single density but the IBM floppy disk controller did not.
 
Go read your datasheets and schematics. Note that the 765 requires an external data separator. the PC8477 is fully integrated (drivers, precomp circuitry and data separators) in that 68 pin PLCC. Said data separator is wired for both FM and MFM. Go to the 5150 controller schematic using the 765 FDC and you'll see that pin 26 on the 765 is NC.

Interestingly, clone makers who used the WD9216 (or its UMC clone) data separator in conjunction with the 765 could, with simple cut and jumper be made to function for reading in both FM and MFM. In point of fact, there were several third-party cards that used the 765 (e.g. Micro Solutions Compaticard I and II, Flagstaff Engineering, etc.) that were perfectly at home with FM.

The original Intel 82077s could handle FM just fine, but when Intel revised the chip (82077AA-1), they broke FM compatibility. I recall calling Intel on this one and being told by an applications engineer "Who the hell uses FM today?"
MIcro Solutions on the Compaticard IV originally shipped them with the Intel chip and discovered to their horror that the updated chips didn't work the same--and they had been shipping product. Fortunately, NSC had a chip PC8477 that worked just fine and MicroSolutions updated all of the faulty cards free of charge with the NSC chip.
 
Chuck(G) said:
The original Intel 82077s could handle FM just fine, but when Intel revised the chip (82077AA-1), they broke FM compatibility. I recall calling Intel on this one and being told by an applications engineer "Who the hell uses FM today?"
Click to expand...

even 30 years later they are still wrong lol
 
I am interested. Please have a look at this picture:

d.jpg

The right PC contain a P3 board that can handle two FDDs. Each PC has an 1.2 MB, 360 KB, 720 KB and an 1.44 MB FDD on board. The left one has also a DVD onboard, the right has also an HDD (not visible) and a GOTEK on board. My very first idea was to use two FDCs that each can handle four drives and to use Sergey's software. But then this discussion took place:
https://www.vcfed.org/forum/forum/t...-4-floppies-with-dpdt-switches-on-power-cable and I that gave me the idea to create this Multi-FDD card (MFC) that enables a user to switch between six different drives for both the A and B drive, thus twelve drives in total: see message 19. The two MFCs explain the two rotating switches at the right of the DVD drive.

The disadvantage of my idea: the moment you switch drives, you have to change the type in the setup, something that is not needed with Sergey's Monster FDC card (Iassume): The advantages: no extra software needed And I can support more drives. Maybe interesting for people who want to support 8" drives as well: combine my and Sergey's cards and the sky is the limit!

@Sergey: the IBM badged case contains the XI-8088 card I bought from you and it is one of my main work horses.

For anyone, out of curiosity: this case was given to me and this abdge actually says: Manufactured by IBM. Does that ring a bell?

FYI, the Commodore sticker on the right case is not original. Notice it is not the original logo, it's the one after ESCOM took over Commodore and changed their name.
 
Question: can the 82077 or PC8477B still be obtained? I have looked at my usual sources but, not available. Other replacements available?
 
Bah, 6 drives is nothing. I've sometimes considered refitting this system with 6 FD-505 "combo" drives for a grand total of 12. I long ago used it for copying--with 3 controllers, it's possible to perform 3 copies simultaneously with the right software. One of our commercial customers, did, in fact set up a second tower with only power supply and drives for a grand total of 12.
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dhau said:
Disagree strongly. COM port on FDC is a huge bonus. LPT is often on video card (MDA, Hercules, some CGA and EGA). So getting one COM port on FDC is avesome, especially on 5 slot systems.
Click to expand...

On a 5150, yes I see your point. On anything else, meh
 
Here is a 386 I built with 14 floppy drives. 6 of the drives are using SCSI bridges. In the end, however, I removed the 2nd controller. The card had a Motorola floppy controller and was just absolutely horrible for disk imaging.



DSC00158_SM.JPG
 
The problem with SCSI drives is that they're limited to a very small number of formats (like USB floppies). I also thought about stacking Backpack parallel port drives on the same cable, but wasn't sure how many a parallel port could handle before getting weird... :)
 
I agree. The SCSI floppies are really kind of useless. You can't really image with them and there is so little support when it comes to different OS's.

In all reality, If I had my floppy controller wish. I would really like to see someone reproduce the Compaticard IV floppy controller. I'd buy a bunch of those. I really think its the end all beat all of what a floppy controller should be.
 
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