Any interest in a new...

ZWUKOLOW wrote:You can see the same type of connection just with the exception that here it's connected to SCSI ZIP drive instead:

You can do it like that, but have the internal CF reader, unterminated, on one of the middle connectors on the ribbon cable, and have the 2nd adapter like this (on the left, would not need the male to male adapter on the right), on the end of the internal ribbon cable, rather than in the middle of the internal ribbon cable, to replace the original external DB25 connection...

...so that is nearly correct, it just needs the internal SCSI ribbon cable routed a little differently, but you would have to remember to leave an external SCSI terminator plug connected to the external SCSI port, when no external devices are connected, or you would have to open the MPC to set the internal SCSI termination every time you wanted to change from using an external device to not using one, and vice versa.

SimonInAustralia wrote:

ZWUKOLOW wrote:What I actually want to do is to mod it exactly like this:

That is both an ugly solution, with multiple internal adapters, which we are talking about trying to avoid by incorporating the adapters into a redesigned SCSI jack PCB, and I really have my doubts that it will work correctly with external devices, as the internal/external chain is not a single linear end-to-end bus, it becomes a Y-configuration, and then the external chain is not properly terminated.

The SCSI specs say that you can only have a maximum "stub" length to a device off of the main SCSI bus of 10cms. Any external device is going to be much more than 10cms from the internal SCSI bus that it is connecting to, and more if you daisy chain that to additional external SCSI devices.

I would be interested to know if it works properly, especially with an external device or two, as according to the SCSI specs it shouldn't, but that doesn't mean it won't.

Any solution I would come up with would do it properly, and not have the external connector in the middle of the internal SCSI bus like that, it really isn't how it should be done.

Yes it's not a best looking solution, and can be viewed by some as ugly. I used the picture as an example. Better than 1000 words. But we must keep in mind that we must work with a space and dimensions we are left off, 3000 was not designed for what we are trying to achieve. I am really glad for any solution that works.

Once my parts arrive I want to do it is clean as possible. I have a major in mechanical engineering so I am not afraid of any HW modding and I think I can do it nice. I'm just looking for a working solution so I can put it together.

SimonInAustralia wrote:

ZWUKOLOW wrote:You can see the same type of connection just with the exception that here it's connected to SCSI ZIP drive instead:

You can do it like that, but have the internal CF reader, unterminated, on one of the middle connectors on the ribbon cable, and have a 2nd adapter like this (on the left, would not need the male to male adapter on the right), on the end of the internal ribbon cable, to replace the original external DB25 connection...

...but you would have to remember to leave an external SCSI terminator plug connected to the external SCSI port, when no external devices are connected, or you would have to open the MPC to set the internal SCSI termination every time you wanted to change from using an external device to not using one, and vice versa.

I didn't get it, as I said I'm a mechanical engineer and rather like to see / study a one picture / simple scheme than to read a 1000 words and left it for my imagination. It's not your fault however I can't understand why he's an internal drive in the end of the chain and an external port in the middle and still he got it working but you are saying that this would not work and I've to put an internal drive in the middle of the chain and use an external terminator plug on the external port when not using any external device. Am I missing something?

ZWUKOLOW wrote:Here are the links where such a mod was done before and confirmed to be working:

http://www.mpc-forums.com/viewtopic.php?f=4&t=68300

http://www.flickr.com/photos/tazacacao/3659036793/in/set-72157620536161516/

http://www.mpc-forums.com/viewtopic.php?f=4&t=116641

How come that these guys got it working and it is the same method I posted? No internal drive in the middle of the chain?

SimonInAustralia wrote:I either do not understand your solution, or I think you are underthinking this.

How can the external drive be in the middle of the chain, and the internal drive be at the end of the chain?

No, I don't think you are understand.

You are getting hung up on whether the drive is internal or external. It doesn't matter.

You need to think about the solution in terms of installing two internal SCSI drives and then figure out what you need to change to make one of the drives external.

What you would need to change would be the SCSI connector.

You can change connectors easily with adapters or by having a special cable made for your setup.

There are industry standard connectors that you can put on a ribbon cable that will let you hook up to whatever you have. You would need D-Sub IDC connectors or 0.10" IDC connectors and they press into the cable.

Having the external drive located in the middle of the chain allows you to not have to open up the MPC to change the termination when the external drive is not connected.

If you wanted the external drive to be at the end of the termination loop, you could place a termination adapter on the connector when the drive is not present.

MPCHunter wrote:

SimonInAustralia wrote:I either do not understand your solution, or I think you are underthinking this.

How can the external drive be in the middle of the chain, and the internal drive be at the end of the chain?

No, I don't think you are understand.

You are getting hung up on whether the drive is internal or external. It doesn't matter.

You need to think about the solution in terms of installing two internal SCSI drives and then figure out what you need to change to make one of the drives external.

What you would need to change would be the SCSI connector.

You can change connectors easily with adapters or by having a special cable made for your setup.

There are industry standard connectors that you can put on a ribbon cable that will let you hook up to whatever you have. You would need D-Sub IDC connectors or 0.10" IDC connectors and they press into the cable.

Having the external drive located in the middle of the chain allows you to not have to open up the MPC to change the termination when the external drive is not connected.

If you wanted the external drive to be at the end of the termination loop, you could place a termination adapter on the connector when the drive is not present.

Thanks for your input. Could you please confirm that the step-by-step solution I posted on the previous page will be working?

I mean the same connection I posted, nothing added or subtracted.

Would I need in this case a terminator adapter plugged into external port when an external drive isn't used or can I use that setup without any additional terminators plugged?

MPCHunter wrote:No, I don't think you are understand.

You are getting hung up on whether the drive is internal or external. It doesn't matter.

...

Having the external drive located in the middle of the chain allows you to not have to open up the MPC to change the termination when the external drive is not connected.

I don't think that you understand, SCSI is a linear bus, it can't be setup in a T or a Y configuration as in the photos above that have the external SCSI connector in the middle of the internal SCSI ribbon cable.

There is only a single SCSI cable going out the back of the MPC to the external drive.

An external drive can not be in the middle of the SCSI chain, unless you have both a SCSI cable going out to the external drive from the MPC SCSI controller, and then another/2nd SCSI cable coming back into the MPC from the external drive to the internal drive, that is the only way that I can see for the external drive to be in the middle of the chain/cabling.

If there is only a single SCSI cable going out the back of the MPC to the external SCSI drive, the external SCSI drive has to be at the end of the SCSI chain.

We are just going to have to disagree, as I can not see how an external drive can be in the middle of the SCSI bus/chain/cabling/whatever, setting it up as in the photos above in a T or Y configuration is simply not how you hook SCSI cabling up.

ZWUKOLOW wrote:Thanks for your input. Could you please confirm that the step-by-step solution I posted on the previous page will be working?

I mean the same connection I posted, nothing added or subtracted.

Would I need in this case a terminator adapter plugged into external port when an external drive isn't used or can I use that setup without any additional terminators plugged?

The photos above, showing the external SCSI connector in the middle of the internal ribbon cable, are not how SCSI should be hooked up.

In that situation, if you have the external chain terminated at the external SCSI port or external SCSI drive, as well as the internal ribbon cable terminated at both ends (MPC SCSI controller and internal SCSI drive), then you have 3 SCSI terminators on the SCSI bus, when you should only have 2, 1 on each end.

The setup in the photo above will work fine without anything connected to the external port, but once you start hanging anything off that external SCSI port, with the external SCSI port being connected in the middle of the internal SCSI cable, you are creating a T or a Y configuration, and until you test it, no one will know how it will behave, because according to the SCSI specs it should not work.

ZWUKOLOW wrote:I didn't get it, as I said I'm a mechanical engineer and rather like to see / study a one picture / simple scheme than to read a 1000 words and left it for my imagination. It's not your fault however I can't understand why he's an internal drive in the end of the chain and an external port in the middle and still he got it working but you are saying that this would not work and I've to put an internal drive in the middle of the chain and use an external terminator plug on the external port when not using any external device. Am I missing something?

I do not see any evidence in those threads that these solutions were used and tested with an external device actually connected to an external port that is located in the middle of the internal SCSI cable.

Without anything connected to the external SCSI port, in that configuration, it will work correctly with the internal SCSI device.

The problem will be only once you connect an external SCSI device.

I would like to see how well that configuration works with a couple of external devices chained off of the external port, say a CDROM and a Zip drive for example.

ZWUKOLOW wrote:How come that these guys got it working and it is the same method I posted? No internal drive in the middle of the chain?

Did they confirm that the external SCSI chain actually worked, not just the internal SCSI drive?

Did they test it with a couple of SCSI devices chained off the external SCSI port?



Really, you guys should Google SCSI bus and SCSI termination, see if you can find some diagrams or descriptions of how the SCSI bus should be configured, see how it is supposed to be a linear bus, and should not be setup in a T or a Y configuration, as it would be in the photos above.

You would find lots of diagrams and information showing how to configure multiple devices on a SCSI bus, like these...


...the right hand diagram here shows how it should not be setup in a Y-configuration, as it is in the photos above...



If you want to do things incorrectly, that's fine, no one is forcing you do do it the right way, and if it works for you then it isn't really a problem.

If you want to do it correctly, to have the best chance of working well with multiple external devices connected, I would not be doing it as shown above with the extenal connector in the middle of the internal chain.

The setup in the photos above can simply be rerouted with the external connector at the end of the internal ribbon cable, and SCSI termination turned off on the internal drive, but it would always need the external port or last device on the external chain to be terminated.


I know about the methods using multiple adapters floating around inside your MPC, I would rather do it more neatly, and correctly, by having a redesigned SCSI Jack PCB that allows a correct internal SCSI connection, without all the adapters, and it would be nice to have auto switching or manual switching terminators on the external SCSI Jack PCB, rather than having to always remember to keep an external SCSI terminator plug connected when no external SCSI device is connected.

SimonInAustralia wrote:

ZWUKOLOW wrote:Thanks for your input. Could you please confirm that the step-by-step solution I posted on the previous page will be working?

I mean the same connection I posted, nothing added or subtracted.

Would I need in this case a terminator adapter plugged into external port when an external drive isn't used or can I use that setup without any additional terminators plugged?

The photos above, showing the external SCSI connector in the middle of the internal ribbon cable, are not how SCSI should be hooked up.

In that situation, if you have the external chain terminated at the external SCSI port or external SCSI drive, as well as the internal ribbon cable terminated at both ends (MPC SCSI controller and internal SCSI drive), then you have 3 SCSI terminators on the SCSI bus, when you should only have 2, 1 on each end.

The setup in the photo above will work fine without anything connected to the external port, but once you start hanging anything off that external SCSI port, with the external SCSI port being connected in the middle of the internal SCSI cable, you are creating a T or a Y configuration, and until you test it, no one will know how it will behave, because according to the SCSI specs it should not work.

This was meant to be a question for MPCHunter as he seems to have some practical knowledge in this subject. In a reality a theory is sometimes a bit different than a praxis. I am not saying you do not have as you said that you was working with SCSI for a pretty long time in the past and I trust you. But this can be a bit different than working with SCSI in servers although it shouldn't be as both uses the same protocol.

This doesn't mean I don't respect your opinion / knowledge however as you can see this is a bit tricky thing to deal with. Can be that according to paper SCSI specifics this shouldn't work but in a reality it does.

There are at least 3 people from the links above who did it and saying that it works. MPCHunter is suggesting the same as my guy who sold me a CF drive he wrote me the same that it's working for him as well.. So we've at least 5 people saying this set up is working correctly versus one saying this won't work..

I'm puzzled a bit but the best what I can do is to try this at my own risk when my connector arrive. Hope the worst thing it can do is that it won't work at all and nothing will blow out (SCSI fuse, board etc.) I think we have to wait for couple of days for a definitive verdict..

SimonInAustralia wrote:

ZWUKOLOW wrote:How come that these guys got it working and it is the same method I posted? No internal drive in the middle of the chain?

Did they confirm that the external SCSI chain actually worked, not just the internal SCSI drive?

Did they test it with a couple of SCSI devices chained off the external SCSI port?

It has been confirmed to me by man who sold me a CF drive. I sent him an email with the question and send him a link to this topic as well. He said he has it connected the same way as pictured and he can access an external port without any problem.

I don't need to use many devices at once, I'll be happy if I can ocasionaly access some ZIP disk through my ZIP drive. I do not know anyone else using CD-ROMS or other devices besides ZIP these days on the 3000 really.

SimonInAustralia wrote:I know about the methods using multiple adapters floating around inside your MPC, I would rather do it more neatly, and correctly, by having a redesigned SCSI Jack PCB that allows a correct internal SCSI connection, without all the adapters, and it would be nice to have auto switching or manual switching terminators on the external SCSI Jack PCB, rather than having to always remember to keep an external SCSI terminator plug connected when no external SCSI device is connected.

I don't have any other option besides the one I described. I'd rather use a redesigned SCSI PCB as well but no such board has been done yet according to my knowledge. If someone can do it and will offer one for sale, I will be very happy to pay for it. Until then, I have to work with what I have at the moment..

ZWUKOLOW wrote:I used the picture as an example. Better than 1000 words.

Here is a picture...

If just using the internal (blue) SCSI bus, which is terminated at both ends, it is good.



Once you add in the external (red) SCSI chain, which also should be terminated, it is bad, it creates a T or Y configuration.




It might work, but it is not the right way to do it.

By simply rerouting the internal SCSI ribbon cable in the photo above, so that the internal Zip/CF drive is in the middle of the internal SCSI ribbon cable, and the external connector is on the end of the internal SCSI ribbon cable, with a terminator on it (whether on the external port or on the last device connected to the external port), it will be the right way to do it.


This is how it should be done, first with no external device connected and a SCSI terminator on the external SCSI port, then with an external SCSI chain and the last device on the external SCSI chain terminated...





You can see from the last diagram that the same parts are used, just the internal SCSI ribbon cable is rerouted to form a linear bus with the external SCSI chain, instead of a T or Y configuration as in the original photo/setup.

You would need an additional DB25 SCSI terminator plug, to terminate the external SCSI connector when not using any external SCSI devices.

SimonInAustralia wrote:Here is a picture...

Thanks mate, I got it now!

MPCHunter wrote:You are getting hung up on whether the drive is internal or external. It doesn't matter.

You need to think about the solution in terms of installing two internal SCSI drives and then figure out what you need to change to make one of the drives external.

No, I think it does matter if the drive is internal or external.

You are only supposed to have a "stub" length, the distance from the main SCSI bus cable to a SCSI device, of 10cm (4"), this is not long enough for an external device to be connected to the middle of an internal SCSI ribbon cable/bus.

While it may work like that in the real world, a more correct way is to think about the solution is in terms of extending the end of the internal SCSI bus out through the external connector, not simply hanging a single external drive off of the middle of the internal SCSI bus, through the external connector, as if it was just another internal SCSI drive on the internal SCSI ribbon cable.

And if you want to...



...with left over SCSI IDs for two more devices.

SimonInAustralia wrote:Once you add in the external (red) SCSI chain, which also should be terminated, it is bad, it creates a T or Y configuration.




It might work, but it is not the right way to do it.

Simon, what can happen when I will use this type of connection however external device, for example just a single ZIP drive won't be terminated?
I'm not speculating here and you showed a deep knowledge in this field already to not trust you. I'm just curious and want to learn more in this subject.
What can happen to any of the devices in the chain? Cheers.

SimonInAustralia wrote:And if you want to...



...with left over SCSI IDs for two more devices.

Thanks mate, your effort is much appreciated.

SimonInAustralia wrote:

MPCHunter wrote:You are getting hung up on whether the drive is internal or external. It doesn't matter.

You need to think about the solution in terms of installing two internal SCSI drives and then figure out what you need to change to make one of the drives external.

No, I think it does matter if the drive is internal or external.

SCSI devices do not know if they are internal or external. They only know that they are a SCSI device.

SimonInAustralia wrote:While it may work like that in the real world,

This is the world I live in so it works for me.

My suggestion in placing the external drive in the middle of the chain was in a single external and single internal drive setup. Of course, as extra drives are added, the geometry of the SCSI chain has changed.

Going back to the original topic of the thread, I think it's been clearly demonstrated here that a clever cabling solution is much more practical than redesigning the SCSI PCB.

If you don't like slop in your cables and having to use lots of adapters, you will have to have a custom cable built. You can certainly go over the maximum length spec if you can find cables that have a better attenuation spec.

Pulls up a seat at the back of the room...