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XT-FDC project level of interest

glitch

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I guess I've adopted John Monahan's philosophy of one function per board. It makes for a much simpler design and a *lot* easier to debug. Also I think there would less interest in a combination board rather than a single function boards.

The UNIX "worse is better" approach! Agreed, single-function is highly desirable in systems that have ample expansion slots.

Does anyone know if the PC8477B fully supports FM mode? The datasheet says it "can't be guaranteed through functional testing," which sort of sounds like, "it's in there, but we're not testing it because no one cares about FM mode to spend the money on testing" (which is probably valid for 99% of end users). That would make the XT-FDC a better option than my current pick of Adaptec 1522A cards for SSSD 8" disk writing.
 

NobodyIsHere

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The UNIX "worse is better" approach! Agreed, single-function is highly desirable in systems that have ample expansion slots.

Does anyone know if the PC8477B fully supports FM mode? The datasheet says it "can't be guaranteed through functional testing," which sort of sounds like, "it's in there, but we're not testing it because no one cares about FM mode to spend the money on testing" (which is probably valid for 99% of end users). That would make the XT-FDC a better option than my current pick of Adaptec 1522A cards for SSSD 8" disk writing.

Hi
I have no idea. That's a better question for Chuck who is familiar with the PC8477B capabilities. I can only go by what the datasheet says at this point.

Thanks and have a nice day!

Andrew Lynch
 

Chuck(G)

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Yes (I thought I've stated that several times in other threads as well as this one). It supports FM, unlike it's pin-identical cousin, the Intel i82077AA-1. When I contacted Intel about them breaking the FM support when the 82077AA-1 update was brought out, they didn't think it was worth fussing about. Usual Intel attitude.

When Intel started shipping the AA-1, Microsolutions recalled all of the CC IV cards so that they could swap chips. No circuit changes, thankfully.

I'll add one other note about controllers. If you need to handle the oddball Cromemco 8" format that uses 50 MFM-encoded sectors of 128 bytes, the only PC compatible controller that can handle that format is the NSC 8273. Fortunately, it's not terribly hard to find.
 

Stone

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Could you add hardware to read and write copy protected disks? Now that would be truly awesome.
Since there are so many copy protection schemes in use don't you think including something like that would involve analysis and re-engineering of all the porposed schemes to be included in this 'hardware' copy protection buster? Did you forget to raise your hand somewhere in this post? :)
 

NobodyIsHere

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[snip]I'll add one other note about controllers. If you need to handle the oddball Cromemco 8" format that uses 50 MFM-encoded sectors of 128 bytes, the only PC compatible controller that can handle that format is the NSC 8273. Fortunately, it's not terribly hard to find.

Hi Chuck! Thanks! There is room reserved on the PCB for the inevitable feature growth is project will experience. If there is enough demand for it, I think there could be two sockets for the FDC to support the PC8477B and the DP8473 presuming they are fairly similar chips and share most signals. Use jumpers and a local crystal oscillator to customize. Please let me know if you think this is worthwhile.

Thanks and have a nice day!

Andrew Lynch
 

NobodyIsHere

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Could you add hardware to read and write copy protected disks? Now that would be truly awesome.


Hi! I think this is outside the scope of the XT-FDC project. Unless Chuck has some "magical rabbit up his sleeve" that can convert the FDC into a bit sampler like Catweasel I don't see this as viable.

I do recall working on such a project at one time but it fizzled. It would almost certainly be some kind of high speed uC based design and a completely different project.

Thanks and have a nice day!

Andrew Lynch
 

Chuck(G)

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I think some ISA Catweasels are still available--oddly, more so than the PCI Catweasel.

But it's a very different kettle of fish to implement a facility like a CopyIIPC OB--and requires a fair amount of software work.

So no--I don't think it's worthwhile to include it.

Adding a 52 pin PLCC socket for a DP8473 chip for just a single format seems to be a bit extreme, Andrew. The chip is common enough on Future Domain SCSI controllers, as well as several other brands, such as Ultrastor, so the people who need it aren't completely out of luck.

OTOH, if you want to implement the board using an 8473 instead of the 8477, by all means do. They're not that different from a software point of view--the 8473 doesn't support PS/2 or special tape drive mode, but we're not doing a PS/2 controller.

The DIP version of the 8473 seems to be more common than the PLCC version. But the DIP version supports only 2 drives. Signal-wise the two are very close, though the 8473 requires an added 4 capacitors and 2 resistors for the PLL filter. Not a big deal--they're small-valued (see table II on p7 of the datasheet)

More uselsess information, for whatever it's worth. If you can find a ready supply of the PLCC version of the DP8473 (that's the -V packaging), maybe it's the better choice, but the difference is exceedingly small in terms of utility.
 

Malc

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Count me in please, I have an 8 bit hd fdc in my XT which supports 2 drives , love to get a couple for my other machines and supporting 4 drives = awesome :)

Thanks
Malc
 

Chuck(G)

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this might be a odd request but could we extend the ROM socket two pins and add two jumps to allow for bigger ROM's?

What on earth are you going to put in that ROM? Floppy BIOS code isn't that big--it could probably fit comfortably in a 2708. I think Andrew's designing for a 2864 EEPROM anyway.
 

k2x4b524[

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I would definetly want this board, maybe 2 or 3 of them if the price was right. As for his extending the socket 2 pins, couldn't you have an option to put the xt-ide and the xt-fd bioses into one chip? Also, would these be assembled boards? or just pcb? or pcb and parts that need to be assembled to the board? If's it's bare board, i'm off the list, i'd rather have a kit or a assembled board.

What on earth are you going to put in that ROM? Floppy BIOS code isn't that big--it could probably fit comfortably in a 2708. I think Andrew's designing for a 2864 EEPROM anyway.
 

NobodyIsHere

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I would definetly want this board, maybe 2 or 3 of them if the price was right. As for his extending the socket 2 pins, couldn't you have an option to put the xt-ide and the xt-fd bioses into one chip? Also, would these be assembled boards? or just pcb? or pcb and parts that need to be assembled to the board? If's it's bare board, i'm off the list, i'd rather have a kit or a assembled board.

Hi
The XT-FDC would be offered similar to how the XT-IDE V2 is now. You can get the PCB then build and test yourself. Maybe someone will organize a group parts buy and/or make kits, partially or fully assembled boards but I can assure you it won't be me.

Thanks and have a nice day!

Andrew Lynch

PS, Chuck I wrote up a custom part DP8473V (PLCC-52) and added it to the schematic. Both FDCs are on the board now and we can decide on one the other or both later. They use very similar pins so it is an easy tweak. The DP8473V has more analog components which is a bit worrisome though. I wonder how repeatable the circuit is or if its sensitive to part placement, tolerance stack up, etc.
 
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SpidersWeb

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I'd gladly buy this, even preorder, two at the minimum.

Just checking I'm reading the PCB right, there is a second internal connector behind the external connector, so no need to make a special cable for more than two drives?
 

Compgeke

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This here is something I would find interest in, as long as it can be used along side an integrated controller such as the one in a PC-6300 that can't be disabled.
 

NobodyIsHere

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I'd gladly buy this, even preorder, two at the minimum.

Just checking I'm reading the PCB right, there is a second internal connector behind the external connector, so no need to make a special cable for more than two drives?

Hi
The board has two connectors for a pair of internal floppy drives on each for a total of four internal floppy drives. One of the internal connectors is also common with an external connector so if you use it then you would have two internal floppy drives and two external floppy drives. No special cables necessary. Hopefully that makes sense.

Thanks and have a nice day!

Andrew Lynch
 

NobodyIsHere

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This here is something I would find interest in, as long as it can be used along side an integrated controller such as the one in a PC-6300 that can't be disabled.

Hi
That's the plan. I've got IO ports, IRQs, and DMA pins routing to everything that's available. You can make some pretty funky settings with this but the intent is to peacefully coexist with built in controllers. Where is your built in FDC located (0x3F0 or 0x370)? This controller supports both locations.

Thanks and have a nice day!

Andrew Lynch
 

Chuck(G)

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PS, Chuck I wrote up a custom part DP8473V (PLCC-52) and added it to the schematic. Both FDCs are on the board now and we can decide on one the other or both later. They use very similar pins so it is an easy tweak. The DP8473V has more analog components which is a bit worrisome though. I wonder how repeatable the circuit is or if its sensitive to part placement, tolerance stack up, etc.

Shouldn't amount to a hill of beans on programming. Both, incidentally support 2.88M drives (how long has it been since anyone's seen any DSED floppies for sale?). I wouldn't let the analog components bother you--stick with 5% parts and I think you'll be fine--after all, they don't determine timing; they just form a low-pass filter so that PLL doesn't lock onto extraneous noise.

Cheers,
Chuck
 
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