XF551 3.5 conversion question

[venom4728a]

I have an Atari XF551 drive and am considering to 3.5 drive upgrade. I have found a ROM/Firmware upgrade on EBAY, the EBAY AD says you have to:

1)All you need to do is remove the old OS ROM chip from the PCB, insert this new one

2)Next fit a 5.25" to 3.5" drive bracket and install the 720K 3.5" disk drive:

 

My Question is:

1)Do I have to find a 720K only 3.5 inch drive or will a modern 1.44mb floppy drive work because it is backwards compatible to 720k and I only use 720k disks? Has any one tried this?

2)Also is there a reason the xf3.5 cannot support the 1.44mb disk format?

3)I also have a dual floppy drive it has a 5.25hd and a 3.5hd in one half height drive slot, I have heard of people using two drives with the XF551 case is this the style of drive they used, and just had to toggle between the two drives.

 

 

Best Regards

venom4728a

[+bob1200xl]

The XF551 comes with a card-edge connector for the FDD - you will need an adapter to convert that to a dual-row header. Or, you can try crimping a new cable on the board connector. Some 3.5 to 5.25 drive brackets have card-edge adaptors built-in, but Atari saved big money on the cable by making it a short as possible, so it won't usually fit.

 

You can read a 720K disk on a 1.44 but writing is less than optimal. Formatting a 720K disk on a 1.44 may be a crap shoot. I have an XF551 somewhere that has a 1.44 in it and it seems OK for reading/writing. Best to find a 720K drive, actually.

 

Yes, there are lots of reasons why the XF551 cannot support the 1.44 format. With enough time and money you could do it, but why?

 

The 720K and 1.44 3.5s are both 80 track drives. The HD 5.25 is 80 tracks but the 360K is 40 tracks. I have run 720K 5.25s on the XF551.

 

Who is selling this upgrade?

 

Bob

 

 

I have an Atari XF551 drive and am considering to 3.5 drive upgrade. I have found a ROM/Firmware upgrade on EBAY, the EBAY AD says you have to:

1)All you need to do is remove the old OS ROM chip from the PCB, insert this new one

2)Next fit a 5.25" to 3.5" drive bracket and install the 720K 3.5" disk drive:

 

My Question is:

1)Do I have to find a 720K only 3.5 inch drive or will a modern 1.44mb floppy drive work because it is backwards compatible to 720k and I only use 720k disks? Has any one tried this?

2)Also is there a reason the xf3.5 cannot support the 1.44mb disk format?

3)I also have a dual floppy drive it has a 5.25hd and a 3.5hd in one half height drive slot, I have heard of people using two drives with the XF551 case is this the style of drive they used, and just had to toggle between the two drives.

 

 

Best Regards

venom4728a

[ataridano]

 

You can read a 720K disk on a 1.44 but writing is less than optimal. Formatting a 720K disk on a 1.44 may be a crap shoot. I have an XF551 somewhere that has a 1.44 in it and it seems OK for reading/writing. Best to find a 720K drive, actually.

 

 

My understanding is a little different, unlike 5.25" drives, 3.5" drives determine the type of media inserted by checking for the hole in the disk, that is not communicated over the data cable, so when a 720k disk is inserted in a high density drive, it's functionally exactly the same as a low density drive. The only place where I've run into problems using high density drives is on the Amiga, where the controller is looking for a signal on pin 2, which was later used as density select on 1.2M drives. The XF551 won't have this so it won't be a problem.

 

I've never seen a combo drive that could be jumpered to work as a 40 track 5.25, and without compatibility to exchange disks with other atari drives, I saw no point in having the 5.25" mechanism there.

[jaybird3rd]

As I recall, in addition to adapting the data cable from a two-row pin header to the XF551's card-edge connector, you also have to reconfigure the "drive select jumper" on the floppy drive itself. The default setting for PC-compatible drives is DRIVE1, but the XF551 requires DRIVE0. Floppy drive manufacturers have long since stopped putting a physical jumper on their drives for this, but I successfully converted a Sony 1.44MB drive mech for the '551 by finding the solder footprints on the drive's logic board and moving a small resistor. If you're using a 1.44MB drive, you might also modify the drive's density selection switch, which corresponds to the notch in the top of 3.5" floppy disks opposite the write-protect notch. This notch is open for 1.44MB media but closed for 720K media. I simply prevented my drive from ever entering 1.44MB mode by replacing this switch with a jumper wire, ensuring that it is always "closed".

 

That was all I had to do (besides replacing the XF551 firmware) to get a new, bone-stock Sony 1.44MB floppy drive mech to work inside my '551. I haven't used it with enough 1.44MB floppy disks (formatted to 720K) to speak to its reliability, but it seemed to work for me, at least in the short-term. I tend to use 720K media, though, just to be on the safe side, and I haven't had any trouble with this so far.

[spookt]

I won't disagree with Bob as he probably has more experience of doing this than most.

 

One thing you will have to look out for is you'll probably need to change the drive ID of the 3.5 inch mech. I think most are set as drive 1 and the XF expects drive 0. There are usually "solder jumpers" if not real physical jumpers on the board in the mech somewhere which you will have to change. I've done this on a couple of drives and it seems to work fine. If you din't understand what I mean I can dig out a mech and post a picture.

 

(Note: this has nothing to do with the XF551 drive select switch which switches the XF between D1,D2 etc)

[Mathy]

Hello guys

 

You can turn SD into DD disks and vice versa as often as you want. But never turn a 1.44 MB disk into a 720 kB disk or vice versa. Chances are high that the disk can not be used at any density after formatting if the disk was formatted to the other size before.

 

1.44MB drives need a higher frequency crystal then 720 kB drives (probably among other things).

 

If you have to make a cable to connect the drive mechanism to the board in the XF, you can switch around some wires to turn an "ID 1" drive respond to "ID 0". That's probably easier then turning the drive itself from ID1 to ID 0, as these switches/bridges/jumpers aren't always easy to reach.

 

sincerely

 

Mathy

[OldAtarian]

I have an Atari XF551 drive and am considering to 3.5 drive upgrade. I have found a ROM/Firmware upgrade on EBAY, the EBAY AD says you have to:

1)All you need to do is remove the old OS ROM chip from the PCB, insert this new one

2)Next fit a 5.25" to 3.5" drive bracket and install the 720K 3.5" disk drive:

 

My Question is:

1)Do I have to find a 720K only 3.5 inch drive or will a modern 1.44mb floppy drive work because it is backwards compatible to 720k and I only use 720k disks? Has any one tried this?

2)Also is there a reason the xf3.5 cannot support the 1.44mb disk format?

3)I also have a dual floppy drive it has a 5.25hd and a 3.5hd in one half height drive slot, I have heard of people using two drives with the XF551 case is this the style of drive they used, and just had to toggle between the two drives.

 

 

Best Regards

venom4728a

 

NEVER, EVER try to format a HD floppy to single or double density. You are putting your data at risk. This is a problem that comes up in the Mac world all the time when people want to backup their 400k or 800k floppy disks and all they can find are 1.44mb floppies for sale. It doesn't usually work out for very long. Sooner or later you will try to access that floppy and it won't work. Your directory will be scrambled or your data will just be gone. It's hard to find lower density floppies of any size but you really do need them for reliable operation in low density drives.

[+wood_jl]

NEVER, EVER try to format a HD floppy to single or double density. You are putting your data at risk. This is a problem that comes up in the Mac world all the time when people want to backup their 400k or 800k floppy disks and all they can find are 1.44mb floppies for sale. It doesn't usually work out for very long. Sooner or later you will try to access that floppy and it won't work. Your directory will be scrambled or your data will just be gone. It's hard to find lower density floppies of any size but you really do need them for reliable operation in low density drives.

 

True!

 

But low-density floppy disks just a mouse click away!

 

Click here: www.floppydisks.com

 

My LD 3.5" disks got here in 2 days, when I was expecting a week! Top-notch service. Very generic-looking black disks with NO labels, but I was just glad they were available.

[+orpheuswaking]

I think it's a cool mod, but I have to ask... is there any practical reason to do it?

 

 

[spookt]

I think it's a cool mod, but I have to ask... is there any practical reason to do it?

 

Well in my case I was given a broken XF551 some time ago. It appeared to have been dropped since some of the case internals were smashed and the 5.25 inch mech was shot too. Finding a compatible 5.25 inch mech turned out to be difficult in the UK and it sat on the shelf for a long while. I decided to try and get it working and stuck a 3.5 inch mech in it for fun. It's actually kind of cool to have that much storage on a floppy, but I guess with the other storage options around today its really just a novelty. I don't use my stock '551 often since they're fairly rare over here and expensive when they do show up.

Edited September 30, 2010 by spookt

[jaybird3rd]

I think it's a cool mod, but I have to ask... is there any practical reason to do it?

To be honest, I don't use mine very much any longer, particularly now that we have MyIDE and other more modern alternatives.

 

I think the biggest problem with 3.5" XF551 drives is that they require two disks to replace every 5.25" disk that was a "flippy" (such as games that used both sides of one or more disks). Even the HyperXF firmware, which gave you the ability to put up to four "partitions" on one 720K disk, didn't give you the ability to switch from one to the other on the fly. So, you end up with piles of disks that are only 12.5% full, because the old software that's on them wasn't designed to use all of the available space. Having 720K of storage on one disk is great if you need to fill it up with binaries or data files, provided you use a DOS that can support it, but again, MyIDE and other solutions do the job better nowadays.

[tjlazer]

Same for me I got XF551 with a dead mech, so I converted it to use a 3.5" drive and it works great! 720K on a disk is nice.

[+Larry]

Hi Bob-

 

Presume you found the eBay post for the replacement eprom.

 

I am curious about about "writes being less than optimal" using a 1.44 drive. I have always read that the track width was identical with 1.44's and 720K drives. That the only differences were write current and data rate as activated by the HD hole in the disk. Not saying you are wrong, just "why" -- if you have read this somewhere or seen something on a scope. I've never had any reliability/formatting issues with 1.44's, but that's not quite the same thing as not being optimal.

 

-Larry

 

The XF551 comes with a card-edge connector for the FDD - you will need an adapter to convert that to a dual-row header. Or, you can try crimping a new cable on the board connector. Some 3.5 to 5.25 drive brackets have card-edge adaptors built-in, but Atari saved big money on the cable by making it a short as possible, so it won't usually fit.

 

You can read a 720K disk on a 1.44 but writing is less than optimal. Formatting a 720K disk on a 1.44 may be a crap shoot. I have an XF551 somewhere that has a 1.44 in it and it seems OK for reading/writing. Best to find a 720K drive, actually.

 

Yes, there are lots of reasons why the XF551 cannot support the 1.44 format. With enough time and money you could do it, but why?

 

The 720K and 1.44 3.5s are both 80 track drives. The HD 5.25 is 80 tracks but the 360K is 40 tracks. I have run 720K 5.25s on the XF551.

 

Who is selling this upgrade?

 

Bob

[Tempest]

I've got a 3.5" converted XF551 that I've been meaning to sell for a long time now. I never use it anymore and it should go to someone who will. Shoot me a PM if interested.

 

Tempest

[+bob1200xl]

I would be careful about 1.44s, although I did say that I have one and it seems just fine. I don't think all 1.44s are capable of 720K operation and I'm not sure that the controller/drive is smart enough to know when to skew the WriteGate signals. As you seek into the disk, the bits get closer together and tougher to pack, so at some track number (43, if I remember correctly) the drive/controller switches to a different write pattern or some such. I don't believe that the 1.44 and 720K are the same in this aspect. I can't remember if this track switch is in the code or not. Probably not.

 

It is more of a case of what we don't know rather than what we do.

 

We're not talking about diskettes, just drives, right? You still need to use 720K disks - don't defeat the density sensor. I did try 1.44 diskettes and I think they worked pretty well also, but not a good idea. I remember guys used to punch a hole in the 720K diskettes and use them as 1.44s. Ugly...

 

The EPROM was on eBay?

 

Bob

 

 

 

 

 

Hi Bob-

 

Presume you found the eBay post for the replacement eprom.

 

I am curious about about "writes being less than optimal" using a 1.44 drive. I have always read that the track width was identical with 1.44's and 720K drives. That the only differences were write current and data rate as activated by the HD hole in the disk. Not saying you are wrong, just "why" -- if you have read this somewhere or seen something on a scope. I've never had any reliability/formatting issues with 1.44's, but that's not quite the same thing as not being optimal.

 

-Larry

 

The XF551 comes with a card-edge connector for the FDD - you will need an adapter to convert that to a dual-row header. Or, you can try crimping a new cable on the board connector. Some 3.5 to 5.25 drive brackets have card-edge adaptors built-in, but Atari saved big money on the cable by making it a short as possible, so it won't usually fit.

 

You can read a 720K disk on a 1.44 but writing is less than optimal. Formatting a 720K disk on a 1.44 may be a crap shoot. I have an XF551 somewhere that has a 1.44 in it and it seems OK for reading/writing. Best to find a 720K drive, actually.

 

Yes, there are lots of reasons why the XF551 cannot support the 1.44 format. With enough time and money you could do it, but why?

 

The 720K and 1.44 3.5s are both 80 track drives. The HD 5.25 is 80 tracks but the 360K is 40 tracks. I have run 720K 5.25s on the XF551.

 

Who is selling this upgrade?

 

Bob

[spookt]

 

The EPROM was on eBay?

 

Bob

 

I fixed a 3.5 inch XF551 conversion for a fellow AtariAger and I think he got his HyperXF ROM from eBay.

[venom4728a]

 

The EPROM was on eBay?

 

Bob

 

I fixed a 3.5 inch XF551 conversion for a fellow AtariAger and I think he got his HyperXF ROM from eBay.

 

 

Hello and thank you to all who answered my post, I have gotten alot of great information from you all. The Ebay Ad is listed by tjlazah Item number 130437075988

 

I have a bid in on the chip and plan to ask for the HYPERXF upgrade, he says he is offering the Bob Wolley version as well.

 

I purchased a Floppy drive edge connector, it has a JUMPER on the board not sure what it is for, I am hoping it is for drive ID selection. I also purchased a a new floppy drive cable, 5.25 to 3.5 drive bay adapter. I am just getting back in to Atari after a really long pause, I want to install the upgrade because if I remeber right my 551 was working well when it went into storage. I also ordered a SDRIVE and am waiting anxiously for it to be delivered. I have the 32 OS in 1 from Atari Max installed. I am also hoping to get a ULTIMATE1MB, VBXE2, RTIME8, Covox, Simple Stereo, Supervideo SVIDEO Upgrade and the external adapter to work on my Atari 1224 Monitor. I have been into Computers since I gut my first 800 back in 1980 at 8 years old. I have a pretty nice collection of classic computers and plan to MOD most of them to be more useful. I have been reading posts almost daily since i found this website, Its so cool that my atari can still be modded and updated all these years later. My list of Stuff:

 

Atari 800

Atari 800xl

Atari 800xl with 32os in 1

Atari 600xl with 64k upgrade

Atari 1200xl

Atari 130xe

Atari 400

Atari 410

Atari 1020

Atari 1025

Atari 1027

Atari 1050

Atari XF551

Atari XEP80

ICD P:R: Connector

loads of software on floppy and carts

 

Atari 2600 with 100's of carts

 

Amiga 500

 

Atari 520st

Atari 1040st

Atari 1040STFM

Atari 1224 monitor

Atari St 20mb hard drive and a couple external floppy drives

 

Commodore 64, 128 1541/1571

 

TRS 80

 

Colleco ADAM complete system

 

Apple MAC

 

NINTENDO, SNES, GAMECUBE, 64, WII

 

Sega master system, genesis, saturn, dreamcast

 

Sony Playstation 1,2 and 3

 

Xbox and 360

 

Laser disc players, laserdisc movies

 

CED Video disk players and Movies

 

..... too much stuff to go on lol

[+Stephen]

Its so cool that my atari can still be modded and updated all these years later. My list of Stuff:

 

Atari 800

Atari 800xl

Atari 800xl with 32os in 1

Atari 600xl with 64k upgrade

Atari 1200xl

Atari 130xe

Atari 400

Atari 410

Atari 1020

Atari 1025

Atari 1027

Atari 1050

Atari XF551

Atari XEP80

ICD P:R: Connector

loads of software on floppy and carts

 

Atari 2600 with 100's of carts

 

Amiga 500

 

Atari 520st

Atari 1040st

Atari 1040STFM

Atari 1224 monitor

Atari St 20mb hard drive and a couple external floppy drives

 

Commodore 64, 128 1541/1571

 

TRS 80

 

Colleco ADAM complete system

 

Apple MAC

 

NINTENDO, SNES, GAMECUBE, 64, WII

 

Sega master system, genesis, saturn, dreamcast

 

Sony Playstation 1,2 and 3

 

Xbox and 360

 

Laser disc players, laserdisc movies

 

CED Video disk players and Movies

 

..... too much stuff to go on lol

Quite a nice collection!

[carmel_andrews]

Does CSS still do their '551 conversion/mod kits....they did quite a few from what i remember

[flashjazzcat]

CSS Online Catalogue

[+orpheuswaking]

CSS Online Catalogue

 

 

Oh cool, that stuff looks awesome... Hopefully Carmel can get what he's looking for there...

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[flashjazzcat]

CSS Online Catalogue

 

 

Oh cool, that stuff looks awesome... Hopefully Carmel can get what he's looking for there...

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

ROFL.

[oracle_jedi]

I am trying to do the XF551 3.5 mech conversion, and I am confused.

 

I have a 720K drive and the replacement ROM courtesy of TJLazer. I thought it was a straight ROM swap and I read somewhere the ROM is usually socketed.

 

Well my board has a 8050, a WD1772 and no socketed ROM. There is an empty U6 for a 2764 chip.

 

Can I still do the upgrade? What do I need to do here?

[Fox-1 / mnx]

Well my board has a 8050, a WD1772 and no socketed ROM. There is an empty U6 for a 2764 chip.

 

Can I still do the upgrade? What do I need to do here?

 

The 8050 has an internal ROM. On the PCB of the XF is a jumper wire to put the 8050 into 8040 compatibility mode (no internal ROM). In that mode an external (EP)ROM is required, which is U6.

 

Now if I could only remember how to recognize what jumper wire it is.

[oracle_jedi]

Well my board has a 8050, a WD1772 and no socketed ROM. There is an empty U6 for a 2764 chip.

 

Can I still do the upgrade? What do I need to do here?

 

The 8050 has an internal ROM. On the PCB of the XF is a jumper wire to put the 8050 into 8040 compatibility mode (no internal ROM). In that mode an external (EP)ROM is required, which is U6.

 

Now if I could only remember how to recognize what jumper wire it is.

 

OK, so I am going to have to find and move the jumper (any help appreciated!), solder in a socket into the empty U6, insert the ROM and also probably end up re-soldering the floppy connector.

 

Does sound about right?

 

Not quite the simple upgrade I hoped for!

 

Thanks