40p SCSI to 50p SCSI

[sigtau]

While I'm aware that the Powerbook edition of the SCSI2SD does indeed exist, they can only be manufactured in limited runs due to their design being in significantly lower demand than your run-of-the-mill SCSI2SD, per a conversation I had with Interial via PM.  To this end, I took it upon myself to design a PCB that bridges the pinout of the 40-position SCSI connector (at least, the one I have in my powerbook duo 250) to the pinout of a 50-position SCSI ribbon connector, for cases where you may have a v5 board on hand or if you need to test the SCSI header on the board without having to wait for the next run of PB SCSI2SD boards.  I used this link (page 12) to derive the pinout, and then just found various SCSI-50 pinouts online.

Correct me if I'm wrong, but the SCSI2SD boards derive power either from the molex connectors or from the TERMPWR pin on the ribbon cable, so for this project, I left the motor control +5VDC and other voltage sources disconnected, and only pass TERMPWR.

Here is the board design.  I'm ordering a test board to try it out and see if anything fries.

Note: If you try to hook up a mechanical drive to this, you'll need an external power source and there is also no guarantee it will actually work as I'm not supporting that.  This board is dimensionally sized to work with a 2.54mm pitch female IDC-50 header and a male 40-pin header pitched at 2mm.

If I can get it to work, I'll upload the gerber files to github and release it into the wild for you guys to play with.

 

[360alaska]

I’ve been working on something like this, the key is design your board so it doesn’t increase the profile of the board. I’m working to make mine a “top-hat.”

 

[aperezbios]

Let me know how it goes, when you get the board. We actually have some 2.5" PowerBook edition boards in the pipeline, now (finally!), but if this works well, I'd be happy to help finance a run of them, provided the board design is open.

 

[Trash80toHP_Mini]

Missed your post somehow, great project!

I'd just mentioned the prospect of breadboard/tabletop ready version with thruholes for power and DB25. That was as a solution for getting a member's Duo 280 HDD set up for business to start a/o large file transfers when SCSI dockage is unavailable.

Since you're here, how well (transfer rate increase) does SCSI2SD respond to a Fast/Narrow SCSI 2 setup?

 

[Trash80toHP_Mini]

< facepalm >

Sweet! Didn't know about V6. It's too bad I'm totally blowing out the toy budget on BabyPB. Time to eat rice-n-beans for a month again!

 

[sigtau]

I’ve been working on something like this, the key is design your board so it doesn’t increase the profile of the board. I’m working to make mine a “top-hat.”

Yep, mine actually sits underneath the SCSI2SD which may imply needing insulation between the SCSI2SD board and the breakout board. Any stick-on foam pads should do the trick.

Let me know how it goes, when you get the board. We actually have some 2.5" PowerBook edition boards in the pipeline, now (finally!), but if this works well, I'd be happy to help finance a run of them, provided the board design is open.

Absolutely open, under the CERN Open Hardware license.  Gerber files attached below, untested as of yet.

Missed your post somehow, great project!

I'd just mentioned the prospect of breadboard/tabletop ready version with thruholes for power and DB25. That was as a solution for getting a member's Duo 280 HDD set up for business to start a/o large file transfers when SCSI dockage is unavailable.

Since you're here, how well (transfer rate increase) does SCSI2SD respond to a Fast/Narrow SCSI 2 setup?

I have tried SCSI2SD in a beige G3 and it seems reasonably fast.  My biggest issue thusfar has been getting it to prioritize SCSI over IDE in cases where both are present, but that really isn't the SCSI2SD's fault.

To everyone: I actually updated the board design to use larger traces before ordering a batch of 5, here is the revised version (.4mm traces depicted):

I actually ordered two versions, one with .5mm traces and one with .4mm traces.  The half-millimeter ones look like there might be some overlapping traces so instead of trusting the autorouter I just ordered .4mm ones as well to compare.  I'd prefer a thicker trace width for a good connection but that might not end up being perfect, so I'd rather have a working prototype just to be sure.

This looks closer to the hand routed version I attempted earlier, so I'm pleased with the result.  It should arrive in a week so I'll let you all know when it gets here.

View attachment PB40 to SCSI50 MK1.zip

 

[sigtau]

The first batch has arrived!  I'm about to head off for Christmas but I'm going to order the parts from DigiKey or Mouser in my absence and they should be there by the time I get home.

It fits snugly in less than the size of a PB-SCSI hard drive, leaving just enough overhang for the SCSI2SD v5 to fit in the remaining space.

 

[aperezbios]

The first batch has arrived!  I'm about to head off for Christmas but I'm going to order the parts from DigiKey or Mouser in my absence and they should be there by the time I get home.

It fits snugly in less than the size of a PB-SCSI hard drive, leaving just enough overhang for the SCSI2SD v5 to fit in the remaining space.

Fantastic! Would you be willing to send one our way for evaluation? I'll PM you.

 

[sigtau]

Fantastic! Would you be willing to send one our way for evaluation? I'll PM you.

Absolutely.  As I said in PM, I'm building two variants and I want to see which one fits more snugly--SCSI2SD beneath it or above it.  They are cheap to produce individually ($.50 per board, $3 for the connectors) and will likely be dirt cheap in bulk.

The one I have posted here so far fits ABOVE the SCSI2SD.

 

[SDUBjed]

I'd love to know how this worked out - were you successful? do you have any boards available? thank you this is a great idea!

 

[MOS8_030]

Don't they already make these? Or am I misunderstanding what you're trying to accomplish?

https://www.ebay.com/itm/CablesOnline-2-5-Laptop-50-Pin-w-Molex-Power-Cable-to-SCSI-Hard-Drive-Adapter-/270840619638

 

[Trash80toHP_Mini]

As I understand it, the board fits into a 2.5" PowerBook HDD bay and suddenly I just realized I need one!

Have you got any PCBs available for sale? I need one with the drive connector, but not the 50 pin header. It'll be perfect for hardwiring it to the EN/SC NIC in the drive bay of my Duo 2300c.

 

[MOS8_030]

Ah, ok. I think I get it now. Outies instead of innies.

 

[JRL]

I just saw this now - I'd be very much interested in picking up at least 1 of these boards

 

[sigtau]

Oh, hey, this actually garnered interest!

So the first run I ended up accidentally orienting the plug incorrectly and--if I hadn't noticed sooner--would have almost fried my v5 SCSI2SD.  It's my mistake because I think I expected the mini-scsi connector to be oriented one way when sketching the schematic, then oriented the PCB backwards.

As it's very cheap to manufacture the boards I plan on doing a second, revised run this month.  If you want one, reply to this thread or PM me as I have a e-mail notification for this thread, I'll get to you when the time comes here in May.

 

[Trash80toHP_Mini]

Sounds good! Glad to hear you got things straightened out before releasing magic smoke.

 

[sigtau]

Don't they already make these? Or am I misunderstanding what you're trying to accomplish?

https://www.ebay.com/itm/CablesOnline-2-5-Laptop-50-Pin-w-Molex-Power-Cable-to-SCSI-Hard-Drive-Adapter-/270840619638

I wasn't aware of these... but now I'm tempted to try them.  I think the biggest issue with these might be that you have to find a short enough SCSI cable to accommodate it, because the v5 only fits horizontally into the bay, rather than vertically, and the laptop's own ribbon cable cannot be turned or twisted without damage because it is designed to fit a particular way.

Also, the PB SCSI is 40 pin, and is being adapted to 50 pin, so this may be useless for the purposes of a powerbook.  Apple being proprietary Apple, as always!

Might help with those early Toshiba laptops, pre IDE...

Sounds good! Glad to hear you got things straightened out before releasing magic smoke.

It definitely would have magic smoked the laptop's scsi chip, at minimum.  The connector was physically flipped, vertically, meaning 5V was shorted directly to GND.  Would not have been pretty, and makes me want to tie the 5V rails together and put them behind a Schottky diode in the next revision.