MODIFY SONY MPF920 DRIVE FOR ATARI USE

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troed
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Re: MODIFY SONY MPF920 DRIVE FOR ATARI USE

Post by troed » Mon Dec 18, 2017 5:52 pm

exxos wrote:
Mon Dec 18, 2017 3:14 pm
Bikerbob wrote:
Mon Dec 18, 2017 3:09 pm
I suppose a little slower? but so what.. never an issue with wrong write.
I don't understand what you are referring to here..... ?
AFAIK your media change fix indicates media change whenever the drive motor has stopped. That's not the same as what original Atari drives do, so I would also expect "slower" disk reads (as in, TOS would re-read FAT more often) with such a fix compared to using an original drive. It is however perfectly secure against corrupted FAT which is why the fix is a lot better than not having it.

(And I do remember having read exactly how Atari solved it but apparently not well enough to be able to describe it, will have to search ... )

/Troed

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Re: MODIFY SONY MPF920 DRIVE FOR ATARI USE

Post by exxos » Mon Dec 18, 2017 6:00 pm

troed wrote:
Mon Dec 18, 2017 5:52 pm
(And I do remember having read exactly how Atari solved it but apparently not well enough to be able to describe it, will have to search ... )
I don't really know which drive do and do not have media change issues.. Have a Epson 480 I think.. Assume it's a original drive which Atari use... I could investigate that drive...

EDIT:
okay what happens with these drives is WP is pulsed low when the disc is ejected.. The drive does seen to have a detect switch in them internally.

The MPF920 also seems to have a extra switch which does not line up with the density or WP holes either. So there must be some sort of media detect in these drives also, but it does not seem to work same way as Atari drives.

So likely this third switch must trigger a monostable or some sort of one-shot circuit in the floppy controller itself somewhere that it sends a WP pulse, which is then what TOS looks for.

In any case, instead of using the motor on signal as I do on the 1772, the transistor (would need to be NPN in this case ) could be fed from this media detect switch, which I'm just going to call it.. So then WP would be set low when the media change switch is broken (turned off).. This would basically emulate the Atari floppy drive then.
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SolderGirl
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Re: MODIFY SONY MPF920 DRIVE FOR ATARI USE

Post by SolderGirl » Tue Aug 07, 2018 4:55 pm

This is a bit older thread, but by coincidence, i have the perfect solution for this.

In principle, what you need is this modification: http://atari.8bitchip.info/flomodam.html

It includes disk change detect and HD detect function.
Sure, you can do the HD detect with a simple wire on most drives, but that has a downside.
Because then, the drive always gives a low signal when a HD disk is in the drive. This is not good,
because when you have a second drive, you need separate wires for them.
Also, with most simple/primitive HD-Mods, the Floppy Controller will be overclocked all the time when a HD disk is in the drive. The AJAX can handle this most of the time, but the WD1772-02 will get quite hot after a while.

But this Drive mod does it a bit diffrently. The drive only gives Low signal on Pin 2 when the drive is active. So the controller is only overclocked when there is drive access. And you can have two drives on one cable, independently of each other. The Mod of the drive also gives the right signal on the WP-Pin so the Atari will see when a disk is changed. The link above shows the mod done in a Chinon drive, i will attach a picture of it done in a Sony MPF920 as requestet in the title.
Attachments
floppy.jpg
floppy.jpg (315.6 KiB) Viewed 548 times

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Re: MODIFY SONY MPF920 DRIVE FOR ATARI USE

Post by exxos » Tue Aug 07, 2018 5:10 pm

SolderGirl wrote:
Tue Aug 07, 2018 4:55 pm
Also, with most simple/primitive HD-Mods, the Floppy Controller will be overclocked all the time when a HD disk is in the drive. The AJAX can handle this most of the time, but the WD1772-02 will get quite hot after a while.

But this Drive mod does it a bit differently. The drive only gives Low signal on Pin 2 when the drive is active. So the controller is only overclocked when there is drive access. A
Same things I did on my HD kits. A lot of mods failed because they ran the 1772 in 16MHz all the time, so they would overheat and start to fail. Running them in 16Mhz only when the drive is active in HD mode means 1772's which would otherwise fail, actually work pretty well.

Later kits had the media fix built on as well.
viewtopic.php?f=12&t=47

Of course some other media fixes I did on drives viewtopic.php?f=12&t=428
4MB STFM 1.44 FD- VELOCE+ 020 STE - 4MB STE 32MHz - STFM 16MHz - STM - MEGA ST - Falcon 030 CT60 - Atari 2600 - Atari 7800 - Gigafile - SD Floppy Emulator - PeST - HxC - CosmosEx - Ultrasatan - various clutter

https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/last/storenew/ - All my hardware mods for sale - Please help support by making a purchase.

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francouai
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Re: MODIFY SONY MPF920 DRIVE FOR ATARI USE

Post by francouai » Sat Oct 20, 2018 8:37 am

I confirm, you cannot use a PC disk drive and use it into Atari without Mod.
I just did a quick test using my PC internal floppy drive to my MSTE and .. nop. :D
I also used a Amiga drive into my MSTE and... nop :lol:
--
Francouai

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