BlueSCSI v2 Pico - Low cost, open hardware, fast SCSI device!

[JDW]

The only thing missing from the discussion of the DB25 edition is the fact it is quite a bit larger than the BlueSCSI v1 DB25. When used internally, that shouldn't matter, but when used externally, it means you would need to have a rather significant amount of space between the back of your vintage Mac and a wall.

 

[Yoda]

That wouldn't be an issue for me, and I think even if it was, the ability to hot-swap microSD cards while its running would encourage me to re-site my Mac!

In almost every case, my BlueSCSI devices will be internal, so that hot-swap capability, which I really like the sound of, won't actually help in a practical sense.

 

[JDW]

Not every vintage Mac can be moved to a new location that is further away from a wall. This is simply an observation relative to the physical size of BlueSCSI v1 DB25, and should not be misconstrued as a knock against v2, which is absolutely amazing in terms of performance. And I don't say that flippantly either, as I am BIG on performance!

But of course, if v2 every goes through a PCB shrink in the future, it would benefit the DB25 version the most. The v1 DB25 really is small and cute and fits in most any shirt pocket quite easily. For external versions, smaller is always better.

 

[retr01]

Using the BlueSCSI v2 DB25 barely fit behind my P476 since I am using almost all of the ports connectors. A right angle upwards may be more suited so that it narrows down to only the connector for more room between the other connectors and between the back of the computer and the wall.

 

[François]

The only thing missing from the discussion of the DB25 edition is the fact it is quite a bit larger than the BlueSCSI v1 DB25. When used internally, that shouldn't matter, but when used externally, it means you would need to have a rather significant amount of space between the back of your vintage Mac and a wall.

Is there a reason to plug the external BlueSCSI directly at the back of the computer? Could you use a cable, like a normal external SCSI device?

As existing SCSI DB-25 to DB-25 cables are male-male (like for SCSI Zip drives), you’ll have to replace the DB-25 on the BlueSCSI with a female one. Easy to do when you’re building it yourself!

Or do I miss something? (I’m not a SCSI specialist at all!)

 

[PotatoFi]

Is there a reason to plug the external BlueSCSI directly at the back of the computer? Could you use a cable, like a normal external SCSI device?

As existing SCSI DB-25 to DB-25 cables are male-male (like for SCSI Zip drives), you’ll have to replace the DB-25 on the BlueSCSI with a female one. Easy to do when you’re building it yourself!

Or do I miss something? (I’m not a SCSI specialist at all!)

You can do this, and I do regularly. I found a short cable with the right connectors, and I keep it with my external BlueSCSI v1.

 

[JDW]

Is there a reason to plug the external BlueSCSI directly at the back of the computer?

Your having asked that question makes me assume you've never used a BlueSCSI v1 DB25 and loved how tiny and compact it is. I also have Stephen A.'s "OverEasy II" external SCSI solution which uses a long ribbon cable, but I've never found that to be a perfect substitute for having a tiny BlueSCSI external you can throw in a bag and grab when you need to quickly diagnose a vintage Mac without even opening the Mac's case. Because the BSv1 DB25 is so small, I never worry about accidentally bumping it off or accidentally bending the SCSI connectors (or cracking their solder joints), and I am relieved of the massive headaches that come with devices attached to the back of Macs near a wall that forces you to move the entire table and Mac(s) away from the said wall.

So yes, there is definitely a use case for a compact SCSI device that attaches to the back of a vintage Mac AND which doesn't jut out too much.

I'm not the first person to think this way. That idea comes from way back in 1989...

Is that awesome? Oh yes... Yes it is!

 

[François]

I should have been more precise, I was thinking of a technical reason, like electric limitations, that would prevent the use of a cable. I can totally see the practical uses of attaching it directly at the back of the case!

 

[JDW]

I should have been more precise, I was thinking of a technical reason, like electric limitations, that would prevent the use of a cable. I can totally see the practical uses of attaching it directly at the back of the case!

I am not aware of anything "preventing the use of a cable" insofar as I successfully use the OverEasy II "cable" adapter by @Stephen to fit between the external SCSI connector of my vintage Macs and BlueSCSI v1 and v2.

I specifically use "Revision B" that is sold by @Kay K.M.Mods but sadly it is currently out of stock on his site here:

商品ページ | infinityproducts

en.infinityproducts.co.jp

OverEasyII "B" is fantastic because it allows me to rapidly test all of my BlueSCSI's and my MacSDs too, to a variety of Macs. Even so, I also have a DB25 BlueSCSI v1 that is cute and compact and highly portable. No need to move my desk or Macs further from the wall with that, or even with OverEasy II "B".

 

[Paolo B]

Dear All,

I have a few SCSI2D devices since some years now. I recently plugged one into an HP 712. Everything runs fine.
However, if I try to use a micro-SD - SD extension cable (I would like to swap the micro SD card without opening the overly fragile top lid every time), the device just stops working.

Now, the issue with the extension cables seems to be somehow documented. But there’s indeed not much about it.
However, the only proposed solution I could find on a Raspberry forum (removing some resistor) did not solve the issue.

I will now test on a BlueSCSI, but it will take me some time.

Do you have any similar experience with either device?
Any suggestion for workarounds?

 

[eric]

the issue with the extension cables

Extension cables seem to be hit or miss, possibly due to length, EM interference, etc. I've had good luck with a random one I bought off Amazon, but I know some have bought the same one and it didn't work for them. I've not seen anything about removing a resistor, if you could share the link you read that on we could take a look.

 

[Paolo B]

Extension cables seem to be hit or miss, possibly due to length, EM interference, etc. I've had good luck with a random one I bought off Amazon, but I know some have bought the same one and it didn't work for them. I've not seen anything about removing a resistor, if you could share the link you read that on we could take a look.

Here’s the link about the resistor tweak. Cable is the very same I got from Amazon.
Honestly, not even that cheap and it seems to be executed in a reasonable way.
I will try to reflow the soldering, but I don’t think it‘s the culprit.
The device is very basic, there are not all that many factors which could make the difference between hit or miss.

 

[JDW]

Here’s the link about the resistor tweak.

Oh. So it seems the "cable" being discussed is the ultra thin ribbon cable of SD card extenders, not a SCSI cable that I had been thinking until now.

I have two SD card extenders and didn't have issues with either in my testing of BlueSCSI v1, although I've not tested them yet with v2 because it uses a full size SD card.

Basically your link is saying to remove the 330Ω resistor on a SD card extender in order to resolve issues. I've not checked my extenders yet to see if they even have such a resistor. What is it, a pull-up?

 

[Paolo B]

Basically your link is saying to remove the 330Ω resistor on a SD card extender in order to resolve issues. I've not checked my extenders yet to see if they even have such a resistor. What is it, a pull-up?

Yes, apparently there’s something wrong either with the flat cable (continuity is OK, though) and / or with the interaction with the SCSI2SD board.
I have understood the resistor is a pull up. There’s also a capacitor and an empty slot for a second one. So it’s not just a mere “electrical continuity” extension, or maybe the passive components are there for the micro - full size SD adaptation.
On YouTube there’s also a gui showing how the extension does not work with hot swap (for camera system), but it’s not my case.
Anyhow, unfortunately I’m not really an expert, so all I can do is to reflow and check that the assembly is properly done, but I don’t think it’s the actual issue.

 

[JDW]

I am not an expert on those cables, so I cannot say exactly what the thinking is. But there is a tiny amount of resistance in any set of wires, and that always means a tiny voltage drop. I doubt there's enough resistance in your typical flat SD card extender to necessitate any special circuitry like a pull-up, but if it is a pull-up, then it must be anticipating some kind of large voltage drop and the cable is trying to keep the voltage high. I've not seen a schematic, so that is just speculation on my part.

 

[Paolo B]

So, some additional info. I just tested the extension cable with BlueSCSI v1.0 on a MacPortable and… it just works.
So, I’d say the issue lays on the SCSI2SD device or, more likely, on the combination of SCSI2SD with the extension cable.
I guess I will order a BlueSCSI v2.0, which seems to be much faster, too, and divert the SCSI2SD (brand new) to some other machine.
Still, it would be interesting to know the reasons why it doesn’t work with the extension cable…

 

[Paolo B]

Tested on two different SCSI2SD, same result.

 

[eric]

We're getting a bit off topic but I opened up my SD Extender and it does have a pull up resistor tied to CLK, and a cap that was connecting the shield to GND, possibly an EMI filter after chatting with @Androda. On the ones that are NOT working if you could (carefully) test the voltage at the extender - you could see if the pull up resistor is doing enough. I'd suggest if we want to continue diving deeper into this we start a new topic on SD Card extenders though

 

[Paolo B]

So, I managed to quickly source a BlueSCSI v2, thanks to the very friendly and effective services of @Kay K.M.Mods.

At first, I quickly tested it on a Portable, which runs on a v1 board.
Note: I switched from SCSI2SD to BlueSCSI on the Portable, as the SCSI2SD would freeze and crash the machine upon waking up from sleep, whereas BlueSCSI v1 seems to be immune from this problem.
Everything worked fine right out of the box. I just swapped the board and the SD card and that was it. It even worked with the cable extender and two adapters in between.
Remarkable.

However, the target machine I have in mind is an HP 712 + NeXT Step 3.3, which so far has been running fine on a SCSI2SD and 4 partitions, 2 Gb each. Installation done from scratch from CD media, formatting the destination virtual device in the course of the installation.

Except that the SCSI2SD is not accepting extension cables, which is much needed for swapping SD cards without opening and closing top lid, whose plastic is now brittle.

Now, how to create correct device images?

At first, as suggested by the Wiki, I tried to use dd for creating empty device images, since in the linked, blank images there’s no 2 Gb cut.
If I create the device images with dd, the installer does not see them.
So, I moved to Disk Jokey. Images are now recognized, but the installer is crashing during the formatting step.

In the log file I can see that:
Configuration file bluescsi.ini file is missing.
Should any .ini file be present in the root directory?

HD Geometry seems to be improperly set.

How to create a working device image and how to get in control of drive geometry?

Thanks in advance for support!

 

[Kay K.M.Mods]

Hi Paolo,

I tested all my BlueSCSI V2 with real Mac SE/30. So far, we have not had any problems with our products other than scratches during PCB manufacturing. The scratched BlueSCSI will not be shipped and will be in my possession forever...

I'm also unfamiliar with what you're trying to do, so I need help from others.
@eric @Androda @OneGeekArmy , any ideas?
If you need an immediate reply, I think it would be a good idea to access Open Retro SCSI/ BlueSCSI/ BlueSCSI-support on discord and ask.

I'll share the 2.048GB file generated already, which has been proven to work on many of my Macs.
Good luck!

PS: Try some SD cards. Some products are incompatible with it.