XF551 and 3.5" High-Density Floppy Drive

[pixelmischief]

Can I use a high-density 3.5" floppy drive on a ROM-upgraded XF551?  I understand that I won't be able to use high-density floppies, as such, but will the drive function with the XF551?

[TGB1718]

I believe it should, as long as you don't use any HD floppys, if you do have any you should cover the extra hole in the disk,

saying that if the disk has been pre-formatted HD, then it may be unusable.

[pixelmischief]

Excellent!  I am working on a super-cool project.  I won't spoil it yet, but I'll definitely post the results when it's done.

[archeocomp]

Floppy drive has no idea what data (which density) is being recorded/read. Most 3.5" HD floppy drives make decision on write current based on the switch sensing extra hole in diskette indicating HD diskette type. They almost always ignore signal DENSEL Pin-2 from controller. That means even when using HD diskette for DD data in HD drive, it will be recorded using (needed) higher current, thus matching increased magnetic coercivity of the diskette material. I have tested it on CP/M system with 100% success and reliability.

Edited August 10, 2020 by archeocomp

[+Larry]

Presume you have the Bob Woolley upgrade article and code or the Hyper XF mod/code.  Bob was certainly first out of the gate with his mod, but at this point in time, I lean toward the Hyper XF.  It is quite a bit faster.  Either one is a very useful upgrade over a stock XF.  The only obstacle that I remember is marrying the XF drive card edge connector to the 34 pins on the 3.5" drive.  Let us know how this turns out for you, and good luck!

[pixelmischief]

2 minutes ago, Larry said:

Presume you have the Bob Woolley upgrade article and code or the Hyper XF mod/code.  

I'm going with the Bob Woolley solution.  If the solution was about speed, I'd just use an SIO2SD.  The tactile feel of the floppy and the beep-beep-beep-patter of disk activity are the things I love. ?

[+bob1200xl]

Some 3.5 FDDs sense the disk density (the extra hole opposite from the Write Protect hole) and set the drive into 720K (DD) mode. Those drives will work with DD disks on an XF551.

 

Otherwise, No. You can't used HD FDDs or HD diskettes in an XF551.

 

Bob

 

[+bob1200xl]

1 hour ago, Larry said:

Presume you have the Bob Woolley upgrade article and code or the Hyper XF mod/code.  Bob was certainly first out of the gate with his mod, but at this point in time, I lean toward the Hyper XF.  It is quite a bit faster.  Either one is a very useful upgrade over a stock XF.  The only obstacle that I remember is marrying the XF drive card edge connector to the 34 pins on the 3.5" drive.  Let us know how this turns out for you, and good luck!

Faster where? SIO? Format?

 

Can you point me to this mod?

 

Thanks!

 

 

Bob

[pixelmischief]

10 minutes ago, bob1200xl said:

Some 3.5 FDDs sense the disk density...otherwise, No. You can't used HD FDDs.

So, if I understand you, I have to find an HD FDD that has this sense ability to use in an XF551?

[cwilbar]

It was my understanding that if you use 720K media, then any PC 1.44 that you can reconfigure to drive 0 would work ?

 

I didn't even know you could do 720K to HD media at HD write current.  If that were to be done, the drive would have to set the write current for the media and not rely on a signal from the computer (in our case, the XF551 mainboard).  Though if it is a logic low or high signal, I presume you could remove that conductor and tie it high (with appropriate pull up resistor), or low ?

 

[+Larry]

Hi Bob-

I did your mod first -- many years ago, then I did the HyperXF.  IIRC (I think I do) your rom runs like the XF551 DS/DD -- 2X SIO.  HyperXF runs at Ultraspeed 3X.  It's not dramatic, but definitely faster.  Here's a link that includes downloadable roms:

 

http://blog.3b2.sk/igi/post/Hyper2b-XF-10-MANUAL.aspx

 

Here's another link at AA (there are lots of discussions here of HyperXF):

 

 

 

 

 

 

[manterola]

Let me add my experience here. The HyperXF firmware actually work slower for me when use an OS with High Speed (HS) modification. My impression is that the computer (with HS OS) ask for change of speed, then the floppy drive answered and they agree to HS change, and then after 1 or 2 sectors at HS transfer rate the floppy drive (maybe the mech is at fault) cannot keep up with the bit rate. 

Then it switch back to normal speed, and then again goes to HS for 1 sector or more or to request HS again, etc. In RespeQt log you can see a lot of requests for HS capabilities and some errors as well.

Let me try this:  It sounds something like pi pi piiiiii piiiiii burp pi pi pi pi piiii burp pi pi pi pi burp pi pi pi piiiiii piiiii burp... So basically it is a mess, nothing regular.

I need to do more experiments to figure out what the problem is, like for example, changing the mech for a modern one (slim) and see if can go better, or maybe it is something related with the skew, which is not appropriate for HS, IDK. But for now , my 5.25" drive works much faster (in seconds) when loading a program in HS.

 

 

[+Larry]

I gotta' ask -- are you sure that your disks were formatted with an UltraSpeed sector layout?  The SDX cart formatter really shines there. I never saw anything like your experience except when a disk was formatted with a regular layout.

[archeocomp]

1 hour ago, cwilbar said:

It was my understanding that if you use 720K media, then any PC 1.44 that you can reconfigure to drive 0 would work ?

 

I didn't even know you could do 720K to HD media at HD write current.  If that were to be done, the drive would have to set the write current for the media and not rely on a signal from the computer (in our case, the XF551 mainboard).  Though if it is a logic low or high signal, I presume you could remove that conductor and tie it high (with appropriate pull up resistor), or low ?

 

There is difference between 5.25 and 3.5 drives. 5.25HD drives set write current as indicated by DENSEL signal. Most 3.5 dont. They follow what they sense on diskette (hole/no hole) to set write current.

[tjlazer]

I hooked up a PC Epson SMD-340 to my XF551 with HyperXF ROM and it works fine as 720k.  If you want to use HD disks you should put some tape on the HD hole so you can ensure the drive sees it as a 720k disk.

[manterola]

Same here with NEC FD3238T Slim Floppy and Samsung SFD-321. Both HD drives, but working correctly @ 720KB

[+bob1200xl]

8 hours ago, pixelmischief said:

So, if I understand you, I have to find an HD FDD that has this sense ability to use in an XF551?

The 1.44 only (no 720K capability) came later in the FDD cycle, I think. Most of the older FDDs would do both densities.

 

I would not use HD floppies in any FDD. If you can't find some DD 3.5s, I have many...

 

Bob

[cwilbar]

2 hours ago, tjlazer said:

I hooked up a PC Epson SMD-340 to my XF551 with HyperXF ROM and it works fine as 720k.  If you want to use HD disks you should put some tape on the HD hole so you can ensure the drive sees it as a 720k disk.

I wouldn't ever do this.  The HD media uses a higher coercivity and requires stronger write pulses to properly write data to the media.

 

Someone in this thread mentioned that many? (or is it some?) 3.5" drives will automatically step up the write current when the HD hole is detected, but that (at least in an XF551) you can format them to 720K.  I had never heard of this, but this would be the only safe way to do 720K on HD media if you want to be sure the higher coercivity media is properly magnetizing the media when writing.  This sounds valid, although I've not personally tried this myself.

 

 

[ijor]

9 hours ago, cwilbar said:

I wouldn't ever do this.  The HD media uses a higher coercivity and requires stronger write pulses to properly write data to the media.

 

Someone in this thread mentioned that many? (or is it some?) 3.5" drives will automatically step up the write current when the HD hole is detected, but that (at least in an XF551) you can format them to 720K.  I had never heard of this, but this would be the only safe way to do 720K on HD media if you want to be sure the higher coercivity media is properly magnetizing the media when writing.  This sounds valid, although I've not personally tried this myself.

 

Actually it usually works, either way, covering the hole or not covering it. It is even possible to use 3.5 DD disks as HD ones by punching a second hole. But please note that just because it works it doesn't mean it is the recommended optimal condition.

 

As somebody mentioned, most 3.5 drives select the write current automatically by sensing the HD hole. That is the whole purpose of that hole. The main reason that you can still write to 3.5 HD disks using lower write current, is because the difference in the coercivity of the media is rather small. The coercivity on 3.5 HD disks is about 10% higher than the one on 3.5 DD disks. For comparison, 5.25 HD disks have a coercivity more than twice the one of 5.25 DD disks.

 

Most people seem to have quite a success using 3.5 HD disks formatted as DD (720K). So, for casual use is probably good enough. But YMMV. In either case you are using the drive and/or the media in a way that it wasn't designed. I'd definitely would try to find DD media if possible.

 

[+Nezgar]

22 hours ago, manterola said:

It sounds something like pi pi piiiiii piiiiii burp pi pi pi pi piiii burp pi pi pi pi burp pi pi pi piiiiii piiiii burp... So basically it is a mess, nothing regular.

This sounds like errors in the SIO transmission/reception. The Hyper-XF ROM uses a bitrate of 57600 when operating in "ultraspeed" mode, which is higher than the Happy or US Doubler used (54000bps). Often the computer will need speed-limiting capacitors lifted or removed to reliably transmit and receive at the faster rates.

 

In the 800XL, those capacitors are C77 and C78

 

In the XE's they are C77 C78 C103 C104:

[cwilbar]

@Nezgar ,

 

Did you mean C77 and C78 for 800XL ?  That is what the picture looks to show, but your text says C77 and C88.

 

Do the 600XL or 1200XL requires these mods for 'super' speed too ?

 

 

[+Nezgar]

35 minutes ago, cwilbar said:

Did you mean C77 and C78 for 800XL ?  That is what the picture looks to show, but your text says C77 and C88.

 

Do the 600XL or 1200XL requires these mods for 'super' speed too ?

Yes, sorry typo... C77 and C78. (Time to renew my subscription so I can edit that. Edit: done! )

 

Generally the capacitors have been only a 'requirement' on all XL/XE's when going to the really fast divisors like 0-5 using an SIO2PC-USB or the like, but "may" be required at Hyper-XF/Happy/Speedy/USDoubler speeds when encountering the symptoms you describe... (probably 400/800 too, I would assume, not too many using crazy fast divisors on those machines)  It can't hurt, regardless. Easily reversible if you want, just lift one leg of each capacitor.

[+CharlieChaplin]

Well,

 

if I want to read A8 disks or files with a PC floppy drive, I am using a Teac drive - Teac 55 GFR... (1.2MB HD drive), it works very well with Ataridsk and Write ATR.

 

If I want to use a 3,5" drive with my XF551, I am using a Teac drive - Teac HF235, it is a HD drive but it works very well with DD/720k disks. NOTE: I experienced that the number after FD-235HF must be 6xxx or lower, eg. 6291-U, drives with a higher number, e.g. A290 did not work for me. Your mileage may vary though.

 

(And yes, in the past I also used 3,5" HD disks and put a write-protect tab from my 5,25" disks onto the HD-hole and used them as 720k disks. This worked for a while, but after some months or maybe 1-2 years, most of these disks had read errors, so I bought DD/720k disks and used them instead.  Many of these disks are now 10-20 years old and still work fine, so DD disks seem to be the better and longer lasting solution, this counts for 5,25" and 3,5" disks...)

 

[cwilbar]

I prefer to write 40 track Atari disks with a 40 track drive (with Supercard Pro).  Atari doesn't have to worry about half tracks, so I'd rather write a full width track.

 

For writing half track disks (C64, Apple ][), I'd use an 80 track drive and bulk erase the destination diskette first.

 

And for writing 720K onto 1.44M media, the only way I'd think this would be safe is w/o blocking the HD hole, and the controller being able to write 720K density while the drive uses HD media write currents.

I'm still not sure what drives can do that (if it is most, or just some) as I've only read about it here.

 

[Dmitry]

As we all know, computer devices are magical gifts sent to us by the gods, and opening the case can anger them.

In fact, they will sometimes recall the spirit living in the box back to heaven, and you can see the magic smoke delivering the spirit back.

 

But, I dared it, I risked it.  and I have a 3.5" XF551 that works.  Yeah!! wooo hoo! I never report success....boo ya!

 

Of course, I'm terrible at hardware mods and this was no exception.

 

I will share that I did buy an XF551 that had already been modded for 3.5" form factor (had a gotek drive in it), so I didn't need to locate edge connector to 34 pin cabling.

However, the previous owner had cut the molex power and soldered 5v and ground directly to the gotek.

And it was not upgraded with the ROM.

So, I had to swap out rom, and put in HyperXF.  It was socketed.

I had to cut off the gotek drive and re-add a molex connector and then convert that to 3.5" power connector with an adapter.

Previous owner was using non-standard screws, so located a few screws.

 

Finally on the 1.44mb 3.5" drive I bought, it was drive 1, not drive 0.  And no way to change that.  So I scanned through 100's of ebay advertisements for old 1.44mb drives, but looking at the back for a series of jumpers.

There are some old drives - though less than 1% that can be drive select through jumpers. But I only needed one, and after an hour of looking at ads, I found one, purchased it.

 

After it arrived I just needed someone with eyes, got my wife to do it, to jumper it for drive 0.

 

Slapped it all together and it sprung to life.  But I didn't know initially how to format either.  Double Sided, Double density, 256bpm in spartados x, format command.  I'm using 720K disks, not 1.44mb.

 

It all works, I'm pretty happy with it.

 

 

 

 

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