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moulinaie

Mega STE back from hell

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Hi,

 

I got a MegaSTE with some problems: first, it didn't boot at all. When opened, it appears that some liquid dropped on the mother board. I cleaned this and now it boots!

But I still have a problem with the internal Hard Disk interface. The HD that came with it is dead (it stops turning after a few seconds), so I tried with other old disks I have but they are not seen by the system (IDCHECK reports nothing).

 

I saw three dip swithes on the interface board, what are they for?

 

Guillaume.

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I think the Mega STe has a limit on the size of hard drive that can be used internally. You need to find one that is less than 1gb. Maybe your problem relates to SCSI termination though?

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I think the Mega STe has a limit on the size of hard drive that can be used internally. You need to find one that is less than 1gb. Maybe your problem relates to SCSI termination though?

 

I tried both types one under 1GB (270mb) and one over. No reaction. But I imagine that even with a 4GB the system would detect it and return the name in the ACSI list.

 

Guillaume.

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Could well be a termination problem then. Or perhaps an drive ID problem, I'm not sure if the internal drive needs to be a particular ID no. Sadly my Mega STe doesn't have an internal HD, so I don't have much experience on that front. Have you tried posting this on Atari forum?

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Hmm, I'm thinking that even though a STacy or Mega STe can't use over 1 gig with the original

internal SCSI card, they can still access the first gigabyte of data. Anything over is just wasted.

 

These machines are kinda odd though - I used the original Satandisk with my *external* ACSI

port on my STacy, with 2 gig cards and no problems.

 

You're right about termination and parity though - both have to be set certain ways for any

drive to work with them.

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I have an UltraSatan plugged into the external ACSI port on my MSTE and that has an 8GB card in it. All of it is accessible. I believe the 1GB limit is only on the internal SCSI bus?

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I tried both types one under 1GB (270mb)

 

270MB. This sounds like a typical size for an IBM disk. If so, most (all?) these are SCSI-2 disks and require a host adapter that provides a parity bit. The stock ACSI interface doesn't provide it but a parity generator can be added to it afterwards.

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I tried both types one under 1GB (270mb)

 

270MB. This sounds like a typical size for an IBM disk. If so, most (all?) these are SCSI-2 disks and require a host adapter that provides a parity bit. The stock ACSI interface doesn't provide it but a parity generator can be added to it afterwards.

 

If I use a disk with a parity jumper, what should I select?

 

Guillaume.

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Hello Moulinaie,

 

To me it looks like you misunderstand.

The Atai SCSI interface does not have parity.

So you must add this to the interface and choose if you select odd or even parity to the correct SCSI-line.

If memory serves right, this is a 74LS260 circuit.

 

Then you can set the HDD to the correct setting.

 

It should be possible to find a description on www :)

 

BR/

Guus

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If memory serves right, this is a 74LS260 circuit.

 

74LS280

 

 

It should be possible to find a description on www :)

 

It's possible now :-)

 

2dwg61i.jpg

 

(tags: atari megaste parity scsi acsi 74ls280 termination)

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Unless I miss my guess, this would apply to the STacy as well, which has the same

internal board/setup.

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Unless I miss my guess, this would apply to the STacy as well, which has the same internal board/setup.

 

It should work with any SCSI-1 compatible bus. I originally did this trick on my Black Box SCSI-1 port for the Atari 8-bit. Actually, at first I only did it in theory as I didn't have the 74LS280 laying around. I knew Marius had an ICD SCS-link 2 (if that's how it's named, but it supports parity disks) and asked him to open it's terminator block to check what's in it. There appeared to be this same parity generator.

 

Since he was at it and also happened to have a ZIP drive laying around which required a parity host he took the IC from the ICD link and soldered it onto his Black Box to check the theory. Seemed to work.

 

At the meanwhile both my Black Box' have this mod and also made one for someone his classic Mac and never came across any problem.

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Hello Moulinaie,

 

To me it looks like you misunderstand.

The Atai SCSI interface does not have parity.

So you must add this to the interface and choose if you select odd or even parity to the correct SCSI-line.

If memory serves right, this is a 74LS260 circuit.

 

Then you can set the HDD to the correct setting.

 

It should be possible to find a description on www :)

 

BR/

Guus

 

Ok thanks, looks like I really was misunderstanding.

Now it's clearer.

 

So I need an old disk that don't use the parity...

 

Guillaume.

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Hello Guillaume,

 

Using a HD without partity is one option.

But that may limit your choices of HD's.

So the alternative is to add parity to the controller. And it's not very hard to do, as you can see in post #10.

Of course you do need to be able to use a soldering iron.... Or ask someone to help.

 

BR/

Guus

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