Any interest in a new...

Is there any interest here for a new MPC3000 SCSI card? Im thinking about the little card that connects to external drives, should be easy to add an internal SCSI port to it with a new design.

Please comment!

Dj Khayos wrote:Is there any interest here for a new MPC3000 SCSI card? Im thinking about the little card that connects to external drives, should be easy to add an internal SCSI port to it with a new design.

Please comment!

I have considered it, and have though about just hacking the existing SCSI JACK PCB to provide this myself in the last couple of weeks.

I want an internal connection from the SCSI/D IN PCB for a 50 pin SCSI ribbon cable to an internal SCSI device(s), which then has to be converted to the 25 pin external DB25 external SCSI connector.

In this situation you really have to consider SCSI termination, as each end of the SCSI bus needs to be terminated.

There is already permanent internal SCSI termination at the MPC end, on the SCSI/D IN PCB.

When using it normally, you would attach an external SCSI device, or devices, and the last device on the external SCSI chain would have to be terminated, either with an external SCSI terminator plug, or some sort of internal SCSI termination on the device, usually either a switchable circuit or plugin resistor packs on the device. If the external SCSI port is not being used, then SCSI termination does not matter, as the SCSI bus is not being used.

When re-routing the external connection to an internal SCSI device, then looping from the internal SCSI device back to the original SCSI port on the rear of the MPC, you need to work out how to handle the SCSI termination at the external SCSI connection.

If you have an external SCSI device connected, you would have to have the SCSI termination turned on in, or attached to, the last external SCSI device on the SCSI bus.

If you have nothing connected the the external SCSI port, you would have to ensure that the internal SCSI device was terminated. This would require setting SCSI termination on the internal device, or connecting a SCSI terminator plug to the external SCSI port on the MPC, at all times that you want to use the internal SCSI device.

So, if re-routing SCSI to the internal SCSI device, then to the external port, you would have to decide how to terminate at the external port, whether by a plug in SCSI terminator plug being attached to the port externally, or by working out a switchable SCSI terminator circuit, or even auto-sensing, to attach on/near the the external SCSI port internally.

Probably the easiest way would be to utilise the internal 26 pin ribbon cable/connector that attaches the SCSI/D IN PCB to the SCSI JACK PCB.

This ribbon cable has a removable connector at the SCSI-D IN PCB end, but looks like it might be hardwired at the SCSI JACK PCB end.

You would need a new 26 pin internal ribbon cable/plug that plugs into the existing 26 pin socket on the SCSI-D IN PCB, that connects it to an internal SCSI device, which would need the 26 pin internal ribbon cable to be converted/adapted to a 50 pin internal connector/cable for the internal SCSI device, then converted/adapted back to a 26 pin socket so that the existing 26 pin cable/plug that is connected to the SCSI JACK PCB can plug into.


A harder, but cleaner way, might be to create a new SCSI JACK PCB, which has a pair of 50 pin internal SCSI sockets in between, and breaking the circuit, in between the 26 pin connection from the SCSI/D IN PCB and the external SCSI port.

When using an internal SCSI device you could connect a 50 pin ribbon cable from one of the 50 pin sockets on the NEW SCSI JACK PCB to the internal SCSI device, and looping back to the second 50 pin socket on the NEW SCSI JACK PCB.

When using no internal SCSI device you would connect a short 50 pin internal ribbon cable between the 2 x 50 pin sockets on the NEW SCSI JACK PCB, thereby ensuring that the external SCSI port is still active.

This would need an external SCSI terminator pack, or internal SCSI terminators or some sort of manual/auto SCSI terminating circuit, to be added to the NEW SCSI JACK PCB when using an internal SCSI device without an external/terminated SCSI device being connected.


They are my thoughts from thinking over this problem over the last couple of weeks.

If you wanted to really go OCD on it, and had the skills, you could add in a couple of IDE/ATAPI and SATA bridges/ports, and even plugin blade SSD ports and CF/SD card sockets, on the NEW SCSI JACK PCB, with selectable on/off/SCSI-ID per port.

My thinking goes like this -> MB -> New SCSI board mounted with external dsub 25 (like the OG) and then traces -> internal SCSI port on PCB with a terminator switch on the PCB!

The PCB is going to be a little bigger but I don´t see no problem!

And yeah I have been thinking about this a long time to, it would make internal mounting so clean!


Responses please!

SimonInAustralia wrote:If you wanted to really go OCD on it, and had the skills, you could add in a couple of IDE/ATAPI and SATA bridges/ports, and even plugin blade SSD ports and CF/SD card sockets, on the NEW SCSI JACK PCB, with selectable on/off/SCSI-ID per port.

It´s not impossible, but is it worth it?
The OS limits! Where´s Rohan at when you need him?

Dj Khayos wrote:My thinking goes like this -> MB -> New SCSI board mounted with external dsub 25 (like the OG) and then traces -> internal SCSI port on PCB with a terminator switch on the PCB!

The PCB is going to be a little bigger but I don´t see no problem!

And yeah I have been thinking about this a long time to, it would make internal mounting so clean!

Having an internal switch on a PCB for external termination would be a hassle to get to if you wanted to attach an external SCSI device.

If you did not know it was there, another user on the MPC, or if you forget about it years down the track, might cause problems.

Any switch would have to be externally accessible, and labelled.

Might not be as simple as just a single port on the SCSI PCB, not sure if that would work properly, as SCSI is usually a bus, with devices attached along the bus, and termination at each end. Having a single internal SCSI port, and an external SCSI port/bus, is going to create a T configuration, rather than linear bus.

Also, where would the SCSI terminators go, and work correctly, in a T configuration?

Dj Khayos wrote:

SimonInAustralia wrote:If you wanted to really go OCD on it, and had the skills, you could add in a couple of IDE/ATAPI and SATA bridges/ports, and even plugin blade SSD ports and CF/SD card sockets, on the NEW SCSI JACK PCB, with selectable on/off/SCSI-ID per port.

It´s not impossible, but is it worth it?
The OS limits! Where´s Rohan at when you need him?

A lot of things I want to do would not be worth it to anyone else (SCSI/CF reader in ASQ10, or hacking a EB16 to give external digital effects sends/returns instead of the on-board effects, in an MPC2000/2000XL, for example).

No OS limit, simply a total number of SCSI devices on the SCSI bus limit, which I think is 7...8 total (SCSI ID 0-7), one being used by the MPC (SCSI ID 6)?

SimonInAustralia wrote:

Dj Khayos wrote:My thinking goes like this -> MB -> New SCSI board mounted with external dsub 25 (like the OG) and then traces -> internal SCSI port on PCB with a terminator switch on the PCB!

The PCB is going to be a little bigger but I don´t see no problem!

And yeah I have been thinking about this a long time to, it would make internal mounting so clean!

Having an internal switch on a PCB for external termination would be a hassle to get to if you wanted to attach an external SCSI device.

If you did not know it was there, another user on the MPC, or if you forget about it years down the track, might cause problems.

Any switch would have to be externally accessible, and labelled.

Might not be as simple as just a single port on the SCSI PCB, not sure if that would work properly, as SCSI is usually a bus, with devices attached along the bus, and termination at each end. Having a single internal SCSI port, and an external SCSI port/bus, is going to create a T configuration, rather than linear bus.

Also, where would the SCSI terminators go, and work correctly, in a T configuration?

No there should not be a prob with an internal term switch since if there isn' t an internal drive you just terminate the external drive(end of scsi chain?).

Other wise the external is mid chain. MPC MB->DB25->INT.

Dj Khayos wrote:No there should not be a prob with an internal term switch since if there isn' t an internal drive you just terminate the external drive(end of scsi chain?).

Other wise the external is mid chain. MPC MB->DB25->INT.

What happens if there is an internal drive, and no external drive, so you need some sort of internal termination at the internal drive end of the SCSI bus...but then you want to plug in an external SCSI device, wouldn't you have to open up the MPC just to turn off termination using the internal switch?

I don't understand how the external can be mid chain, in the normal operation of a linear SCSI bus.

Are you talking about creating a T configuration? If so, will that work correctly?

I have never seen SCSI setup in a T configuration, rather than a linear bus with termination at each end, and all SCSI devices in between...
TERM---DEV---DEV---DEV---DEV---DEV---DEV---DEV---DEV---TERM

It might work, as the internal SCSI chain would not be very long, I have just never seen it done that way.

In all the time I have worked with SCSI, I have viewed it as a linear bus, as above, with termination only at each end, and devices linked from device to device in between.

I think you guys are overthinking this.

What you need is a internal dual device cable with the connectors spaced appropriately. This may be a custom build if you don't want to use adapters, though you may be able to find something that would work in your system.

The chain would have to go:

SCSI Controller -> External Drive -> Internal Drive (Termination).

The internal SCSI drive would be at end of the cable chain and terminated.

The external SCSI drive would be in the middle of the cable chain and would not have to be terminated.

What you are trying to do is not any fundamentally different than below where there is a Hard Drive and Zip Drive installed inside:

http://mpc3000.com/zip_install.htm

MPCHunter wrote:I think you guys are overthinking this.

What you need is a internal dual device cable with the connectors spaced appropriately. This may be a custom build if you don't want to use adapters, though you may be able to find something that would work in your system.

The chain would have to go:
SCSI Controller -> External Drive -> Internal Drive (Termination).

The internal SCSI drive would be at end of the cable chain and terminated.

The external SCSI drive would be in the middle of the cable chain and would not have to be terminated.

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?

In your solution, as the SCSI controller is inside the MPC, that would have to connect out of the MPC to the external drive, then back again to an internal drive inside the MPC, I do not understand how you think this connection can be made, or I am totally not understanding what you are recommending we do.

MPCHunter wrote:What you are trying to do is not any fundamentally different than below where there is a Hard Drive and Zip Drive installed inside:
http://mpc3000.com/zip_install.htm

The difference is that there are two internal devices in that solution, with no external devices, the external connection has been re-routed to the internal drives.

That solution converts the existing external DB25 connector and re-routes it to be an internal IDC50 ribbon cable, which ends at an internal drive that is terminated. There is no longer an external SCSI connection.

We need to also then convert back from that internal IDC50 ribbon cable, from the last internal drive, to an additional external DB25 connector, as the original external DB25 connector is being connected/adapted to the internal IDC50 ribbon cable already.

Then, when the external port has nothing connected, it has to be terminated, and the termination removed when any external devices are connected.

This is to have a working external SCSI port, with a working internal drive, but (in my opinion) has to work both with an external drive connected and without.

As I mentioned in my introduction topic, I am currently working on the mod where you can access internal CF drive and external port in the same time.

I am mostly self-educated and learning on the move so my knowledge is probably not so deep as you guys have.
I am learning from others and use trial & error method into practice.


Currently I have my MPC3000 internally modded exactly like SEED78 has in this topic:
http://www.gearslutz.com/board/rap-hip-hop-engineering-production/480731-mpc-3000-card-reader.html




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




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





For this connection you would need:
(Tthis covers cable connection among internal drive - ext connector - SCSI board only.
Internal drive, IDE-SCSI bridge or power connections for this mod aren't listed.)

(1) IDC50 internal ribbon cable 3 connector for 2 devices (1x):




(2) external DB25 Male to Male adapter:




(3) and external DB25 to internal IDC50 adapter (2x):





Connection:

You connect your SCSI board to DB25 Male-Male adapter and then to to DB25 to internal IDC50 adapter which you mount on the MPC's support foot in the middle of your chasis as can be seen from these pictures:




Then you mount second DB25 to internal IDC50 adapter in the place where you original external SCSI connector used to be. In the end you connect the first adapter to second adapter and CF drive in the end with a ribbon like MPCHunter suggested in the previous post. Like in the picture posted above:





Done



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



I still did not complete the mod as I'm waiting for my adapters to arrive from the US. I should get them pretty soon.
I will let you know when I get my 3000 done how it turned out.

Peace!

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.