Modified Sergey's floppy controller for quad floppy support

[sorphin]

Hello all,

(Let me preface this first that kicad is new to me, I use diptrace normally)

Due to the need to support multiple floppy drives for a 486 machine that I built and being unable to find any floppy controllers that actually support more than 2 drives or that properly support secondary controller duty I decided to take a stab at modifying Sergey's controller to support four drives since his BIOS already supports it and the chip already supports it. Here is a link to the GitHub with the modified files and the gerbers. I would appreciate it if anyone (especially Sergey) can take a peek at it and see if they see that if there's anything that I have missed or may not work. I have modified it to add the second connector as well as selecting between two addresses, two DMAs, and four irqs. Removed the serial port functions. If it looks good I was planning on doing a small run for myself but I will have some extra boards if anyone is interested. I know it doesn't look elegant, as long as it works.

Github link: https://github.com/sorphin/Modified_XT-FDC_ForQuadFloppies

Renders and new schematic attached.

Thanks,
sorphin

 

[Chuck(G)]

Given the limited space inside a case, I'm wondering why floppies 3 and 4 weren't brought out on a rear-bracket connector, say a DC37F. The 9 pin connector doesn't seem to go anywhere.

 

[maxtherabbit]

what's the purpose of allowing other IRQ and DMA than 6/2? I don't think there is any software out there that will accept that (except maybe the windows NT floppy driver?)

 

[maxtherabbit]

Given the limited space inside a case, I'm wondering why floppies 3 and 4 weren't brought out on a rear-bracket connector, say a DC37F. The 9 pin connector doesn't seem to go anywhere.

also this - digikey sells premade DC-37 slot brackets too

https://www.digikey.com/product-detail/en/keystone-electronics/9200-5/36-9200-5-ND/317287

 

[Chuck(G)]

what's the purpose of allowing other IRQ and DMA than 6/2? I don't think there is any software out there that will accept that (except maybe the windows NT floppy driver?)

22Disk etc. has always had provisions for alternate port, IRQ and DMA. So there's that. My old copying utility, SyDupe could take advantage of that and run three diskette copies simultaneously.

 

[sorphin]

Given the limited space inside a case, I'm wondering why floppies 3 and 4 weren't brought out on a rear-bracket connector, say a DC37F. The 9 pin connector doesn't seem to go anywhere.

My case is a tower with enough drive bays. 9 pin conn was left for mounting bracket and is optional to use a normal keystone just like sergeys original.

 

[sorphin]

what's the purpose of allowing other IRQ and DMA than 6/2? I don't think there is any software out there that will accept that (except maybe the windows NT floppy driver?)

because flexibility.. if i'm going to do this.... see the thread where someone added an original one and had to change dma due to conflict... and rewire.. this makes that easier. *shrug*

 

[Chuck(G)]

My case is a tower with enough drive bays. 9 pin conn was left for mounting bracket and is optional to use a normal keystone just like sergeys original.

So keep the second header and add the external DC37 connection as well. You wouldn't be the first to do so.

 

[maxtherabbit]

My case is a tower with enough drive bays. 9 pin conn was left for mounting bracket and is optional to use a normal keystone just like sergeys original.

Keystone makes a standard bracket for the DC-37 also, see the link I posted above.

 

[maxtherabbit]

22Disk etc. has always had provisions for alternate port, IRQ and DMA. So there's that. My old copying utility, SyDupe could take advantage of that and run three diskette copies simultaneously.

Ok I remember using 22disk with port 370 but must have overlooked the DMA and IRQ options

 

[Al Kossow]

A couple of things I see with your layout

- the clearance between the IDC and socket for the 10uF bypass cap is really tight
- how much clearance do you have between cards for those two vertical 10K resistors?

 

[ibmapc]

So keep the second header and add the external DC37 connection as well. You wouldn't be the first to do so.

I am 110% with Chuck here. Optional external floppies are very useful. I use an external 3.5" drive with My 5155 just because I don't like the way a non-original drive looks with it. I've even modified it to get power from the ribbon cable through the DC37.

 

[sorphin]

I am 110% with Chuck here. Optional external floppies are very useful. I use an external 3.5" drive with My 5155 just because I don't like the way a non-original drive looks with it. I've even modified it to get power from the ribbon cable through the DC37.

Got a pinout for this 37 pin deal? Never used one and i'd rather not trace out my 5150/5160.

 

[sorphin]

A couple of things I see with your layout

- the clearance between the IDC and socket for the 10uF bypass cap is really tight

That's sergey's doing? from the original.

- how much clearance do you have between cards for those two vertical 10K resistors?

it'd fit 1/8w 10k maybe 1/4w.. they're needed as pullups for the 74125.. kicad won't let me move things without completely redrawing traces.. (diptrace does, but kicad -> diptrace doesn't go right).. i'd rather have used diff resistors but it was hard enough to make room for those without even more significant reroutes.

 

[Eudimorphodon]

it'd fit 1/8w 10k maybe 1/4w.. they're needed as pullups for the 74125.. kicad won't let me move things without completely redrawing traces.. (diptrace does, but kicad -> diptrace doesn't go right).. i'd rather have used diff resistors but it was hard enough to make room for those without even more significant reroutes.

Do you have enabled the option that lets you drag traces and automatically nudge groups of them around, etc, instead of making each little segment set in stone? I forget the name of said option but it was disabled by default when I installed it last year.

 

[sorphin]

Do you have enabled the option that lets you drag traces and automatically nudge groups of them around, etc, instead of making each little segment set in stone? I forget the name of said option but it was disabled by default when I installed it last year.

Probably not.. this was/is literally the first time i've used kicad.

 

[Chuck(G)]

Got a pinout for this 37 pin deal? Never used one and i'd rather not trace out my 5150/5160.

Easy, right out of the PC techref:

 

[sorphin]

Easy, right out of the PC techref:

Thanks. Modified it to have a 37 pin external option. Have to move the 2nd internal connector slightly and no mounting hole room now.. I'll push it up tomorrow.. Any other notes?

 

[Chuck(G)]

Well, you might save some space by rotating the 2nd connector 90 degrees and positioning it right in front of the DC37, since the signal lines are essentially straight across. Just a thought...

 

[sorphin]

Well, you might save some space by rotating the 2nd connector 90 degrees and positioning it right in front of the DC37, since the signal lines are essentially straight across. Just a thought...

How's this?