ELCO high density floppy module - anyone had any experience with this?

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frank.lukas
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Re: ELCO high density floppy module - anyone had any experience with this?

Postby frank.lukas » Fri Sep 01, 2017 5:31 pm

A EPSON SMD-300 or 340 must be modify to use with a HD Modul. I have SONY MPF920 also working fine with a HD Modul. The SONY Floppy must be moded too with a wire from the HD Switch to Pin2 on the Shugart Bus. The SONY and the modify EPSON must have with a DD Disk or no DISK a Low and when a HD Disk is in a High over Suhgart Pin2 ...

You can Test your HD Modul. It must be change the FDC Clock from 8 to 16Mhz when Shugart Pin2 is high ...
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Re: ELCO high density floppy module - anyone had any experience with this?

Postby Fujiyama » Sat Sep 09, 2017 10:42 am

frank.lukas wrote:On a PC or Mega STE, Atari TT or Falcon the Computer tells over the Pin_2 the Drive what Drive mode is needed by try to read the Disk.

On a normal ST with all HD Moduls the Drive tells over PIN_2 the FDC what mode is set.


So on normal STs (ST, STF, STFM, (Mega ST?) and STE ) pin 2 on the floppy drive is an input signal, while on the Mega STe, TT and Falcon it's an output signal?
I understand how the floppy drive will output a signal on pin 2, because it's connected to the HD-detect switch, so it changes from "hi" to "low" status according to if a HD (or no floppy) or DD disk is inserted, but in the case of the Mega STe/TT/Falcon: how can the computer send a signal to the floppy drive? Is the drive connected in a different way so that the HD detect switch tells the computer which signal (hi/low) to send back to the floppy?


I would be nice somone build for the Atari ST range of Computer a PC, Mega STE, Atari TT or Falcon Style Modul. I think TOS 2.06 supports that ...[/quote]

Would a Mega STe/PC/TT/Falcon type HD-module make it easier to use non-modified floppy drives with the computer?

Back to the HD-module: does anyone know if there are any differences between the Exxos-HD module (more detailed info here) (UKP 25 + postage) and the Black cat hardware HD-module (EUR 22 + postage)?
Given all the problems I read about the Elco module, perhaps it's better to get one that actually works and plugs directly into the 1772/AJAX socket (well, I desoldered mine and put it in a socket).
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Re: ELCO high density floppy module - anyone had any experience with this?

Postby czietz » Sat Sep 09, 2017 11:13 am

Fujiyama wrote:So on normal STs (ST, STF, STFM, (Mega ST?) and STE ) pin 2 on the floppy drive is an input signal, while on the Mega STe, TT and Falcon it's an output signal?


No, it's the other way around, just as Frank wrote. On the MegaSTe, the TT, the Falcon (and on the IBM PC as well) pin2 on the floppy drive is an input signal. (Consequently, it's an output signal on the computer's mainboard.) It's the job of the operating system to tell the drive to switch to HD. TOS will of course do that on a MegaSTe, TT or Falcon.

In contrast, on these HD modules that allow you to upgrade older Ataris (ST, MegaST, STE) pin 2 on the drive has to be an output signal that tells the HD module to switch between DD and HD. It is done this way because TOS due to hardware restrictions simply can't generate the switch signal mentioned above on an older Atari.

Since PC floppy drives have pin 2 as an input (see above), drives have to be reconfigured or even modded to work with these HD modules that require an output signal. It one was to invent a mod for older Ataris that makes it possible for TOS to generate the appropriate density select signal it would be much easier to use PC floppy drives.

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Re: ELCO high density floppy module - anyone had any experience with this?

Postby frank.lukas » Sat Sep 09, 2017 11:18 am

Fujiyama wrote:So on normal STs (ST, STF, STFM, (Mega ST?) and STE ) pin 2 on the floppy drive is an input signal, while on the Mega STe, TT and Falcon it's an output signal?


On normal ST´s it is a Output Signal from the Floppy to the HD Modul. On MSTE/Falcon and Atari TT or PC´s it is a Input Signal while the System tells the Floppy what Modus HD or DD ...

There are PC Floppy´s that give for DD a High and HD or nothing a Low or the other way round. A EPSON SMD-300 or 340 or a SONY MFP920 must be modified to give a Output Signal on Shugart Pin2 ...


... czietz was a second quicker ...
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Re: ELCO high density floppy module - anyone had any experience with this?

Postby troed » Sat Sep 09, 2017 11:23 am

Some more info regarding that pin 2 confusion here: https://blog.troed.se/2017/01/20/the-ta ... i-mystery/

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Re: ELCO high density floppy module - anyone had any experience with this?

Postby frank.lukas » Sat Sep 09, 2017 11:47 am

Problem by modified a PC Floppy is that you make a connection from the HD identification switch to the Shugart Pin2. The Controller on the Floppy expect a High (or Low) for the Modus over Pin2 from the Shugart Bus, the connection is already there to the Controller Chip. When it not match the Drive will not proper work. You can insert a Transistor to invert the signal from the HD identification switch when it is necessary ...

For a EPSON or a SONY a simple wire will do the job, but for a modern TEAC not -> http://www.wrsonline.de/teac.html
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Re: ELCO high density floppy module - anyone had any experience with this?

Postby czietz » Sat Sep 09, 2017 1:04 pm

As for why this was done in this seemingly strange way (why not let the drive detect the density?), I can only speculate: As far as I know, 5.25" floppies had no notches or holes to indicated HD. So when IBM added HD floppy drive support to the AT, the computer had to tell the drive which density to use. I guess this was simply retained for 3.5" drives so that 5.25" and 3.5" drives could operate on the same interface. Atari probably wanted to use standard (PC type) HD floppy drives and thus did it the same way with a density select output signal generated on the mainboard.

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Re: ELCO high density floppy module - anyone had any experience with this?

Postby Fujiyama » Mon Sep 18, 2017 8:59 pm

Chandler wrote:it would be good to get this module working with something like the Sony MPF920 as they are still freely available and cheap


I've looked around for these locally but they seem completely gone from all major PC outlets. Actually I'm having problems finding anyone selling any 3.5" floppy drives (with the exception of external USB floppy drives). Where have you seen them for sale? Online?
I believe Exxos has stocked up a few for sale.

I dug out my STe today (I'm trying to revive my Mega STe at the moment, so the STe (which works) has been put aside for a while) and tried both floppy drives I have with it: a Sony MPF-520 (which I have for the Mega STe) and a 920-E for the STe. The 520 worked fine (I've just tried it in 720K mode as I don't have the HD module attached), but the 920-E didn't. It spins and the LED lights up, but the STe doesn't "see" it or it just doesn't work.
I took a closer look at it, and like the 520 I had modified it in the same way. It's been so long, but I do believe it has worked. I also cleaned it today, using Q-tips dipped in isopropyl alcohol, gently wiping the heads, but to no avail. I've also tried flipping the 34-pin connector the opposite way, also to no avail.
Then again I read that Exxos has had problems with certain versions of the 920-E, and mine appears to be the one with the problematic Sony IC and dated February 2001. I might have to get myself another floppy drive for the STe.
I know this isn't of much help, Chandler, but I'm awaiting delivery of a HD module from Exxos which I'll use in the STe. I'm anxious to see if it'll let me use both HD and DD floppies with the Sony 920-1 the way it's been modified. I'll post back here when I have more news.
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