Megafile 30 / 60 - what does J4 do?

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6BQ5
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Megafile 30 / 60 - what does J4 do?

Postby 6BQ5 » Sat Feb 09, 2019 9:02 am

The Megafile 30 and 60 have a block of jumpers labeled A through P. This block is called J4 on the Megafile 60 schematic that is floating on the web. I don't know the J[x] reference for the Megafile 30. According to the schematic they are hooked up to P7-P0 of the 8156. Seems like by default P7-P0 is pulled up high via a 2.2kOhm resistor. Jumpering J4 would bring them to ground.

What would this be useful for?

Thanks! :)

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Re: Megafile 30 / 60 - what does J4 do?

Postby czietz » Sat Feb 09, 2019 10:15 am

The Scheibenkleister book has the jumper settings for the SH204/SH205. Maybe they're the same for the Megafile 30?

  • A-B, C-D, E-F: Set the SCSI ID of the controller. Must always be 0 in an Atari HD. Note: This is not the ACSI ID, which can be set separately.
  • G-H: Transfer rate. According to the book, setting the jumper reduces the transfer rate.
  • I-J: Enable extended command set. Don't know what this does.
  • K-L: Not used.
  • M-N: Enable support for disk drives that drive SEEK COMPLETE low during head switching.
  • O-P: Start controller self diagnosis. The book mentions that this doesn't work with the SH204/SH205.

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Re: Megafile 30 / 60 - what does J4 do?

Postby gstoll » Sat Feb 09, 2019 10:38 am

czietz wrote:The Scheibenkleister book has the jumper settings for the SH204/SH205. Maybe they're the same for the Megafile 30?

It is the same, but it is not J4, is J7 on the Megafile.

Look in Chips 'n Chips, (only in german).

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Re: Megafile 30 / 60 - what does J4 do?

Postby 6BQ5 » Sat Feb 09, 2019 6:18 pm

Wow, thanks for the replies! This is good info.

It sounds like these jumpers should be left alone in most cases.

Oh, almost forgot to ask. What is the difference between the controller in the Megafile 30 and Megafile 60? Is there some special functionality missing in the 30?

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Re: Megafile 30 / 60 - what does J4 do?

Postby czietz » Sat Feb 09, 2019 7:01 pm

Again, according to Scheibenkleister the controllers are the same, just the actual hard drives are different -- obviously -- in the Megafile 30 and 60.

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Re: Megafile 30 / 60 - what does J4 do?

Postby 6BQ5 » Sat Feb 09, 2019 7:05 pm

Hmm! The reason I was asking if the controllers are virtually same because the reference designations are different between the two. J4 vs J7 for the jumper connections as sited above. Maybe Atari added some functionality between the two versions?

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Re: Megafile 30 / 60 - what does J4 do?

Postby czietz » Sat Feb 09, 2019 7:12 pm

EDIT No. What Gerhard was saying is that in the SH204, SH205 and Megafile 20, it's J4. (EDIT: According to Scheibenkleister J5.) In the Megafile 30/60, it's J7.
Seems that Chips'n'Chips is wrong here: photos show that it's J4 in the Megafile 30 and 60, J7 in the SH205/Megafile 20, and J5 in the SH204. This matches the description in Scheibenkleister.

Anyway, regardless of the confusion about how the jumpers are named: The board is exactly the same for Megafile 30 and 60.

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Re: Megafile 30 / 60 - what does J4 do?

Postby 1st1 » Sat Feb 09, 2019 10:13 pm

The only difference between SH 205, Megafile 2o on the one side, and Megafile 30/60 on the other side is just one chip which does the drive data encoding, on the SH205/MF20 it is a MFM chip, in MF 30/60 it is the RLL chip. Also firmware is different, related to the different number of sectors on MFM versus RLL. The rest is identical.

Adding a 2nd drive is quite simple, i did it several times. Also the SH 204 controller can handle a second harddisk, but in the shoe box is no space for that.
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