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RaSCSI Development Thread

landoGriffin

Well-known member
You will get very heavily bottlenecked by the SCSI connection in this case.  SCSI-1 is not fast, so do not expect too much...
The Mac is also a significant bottleneck. With a SE/30, I'm happy to get 1MB/s :)  

The maximum theoretical limit on SCSI-1 is 5MB/s, which is much slower than a SD card at 10-12MB/s.

 

cheesestraws

Well-known member
You are right. On another side, i'm more interested about using a real ssd, just because I had bad experiences with SD cards.


For reliability, you are likely right that it will be better; and I can't see any reason why it wouldn't work, so long as you're not expecting a speedup :) .

 

uyjulian

Well-known member
You can also use an eMMC to microSD adapter for your Raspberry Pi. eMMC are more reliable than microSD

 

max1zzz

Well-known member
So my boards arrived a few days ago, unfortunately the bad news is they don't seem to work, both my powerbook 100 and 145B refuse to boot from it, the 74LS641's also seem to be getting pretty warm which doesn't seem right!

I'm a bit lost as to what the issue is right now, I can't see and obvious errors in the board but since this is based on design we know works I must have made a error somewhere!

 

max1zzz

Well-known member
OK..... I think I have found the issue and I'm a little embarrassed as to what it was, turns out it was a cold solder joint on one of the termination resistors..... I designed the board using 0603 resistors forgetting the reel or 110ohm resistors I had where 0805, turns out bodgeing 0805's onto 0603 pads isn't the best idea!

My PB145B now boots from my Pi Zero powered RaSCSI just fine :)

IMG_1196.jpg

And the board (ignore that bodge wire - it is a leftover from debugging and is not needed)

IMG_1197.jpg

I need to add a anti backfeed diode to the +5v rail on the board to stop the Pi trying to power the PB if a external PSU is connected, but apart from that the board seems to work fine :)

 

Trash80toHP_Mini

NIGHT STALKER
Sweet things going on there, max!

You can also use an eMMC to microSD adapter for your Raspberry Pi. eMMC are more reliable than microSD


Could you use the eMMC built into an RPi Compute Module as mass storage for a Mac via RaSCSI?

The new CM 4 is smaller than previous CM versions with a compact interboard connection setup in place of the big edgecard interface of previous CM versions. Seems a better aspect ratio than the Zero? They're more expensive, but the connector setup would snug it right up to the bottom if you made a 45x55mm RaSCSI board? Looks like the assembly could be significantly smaller than a 2.5" HDD bay? I guess without SD you'd need to do data transfers over wireless or USB. With CM 4 w/o eMMC on board you get SD though. Dunno, I'm just along for the ride on this kinda stuff, but thought to mention it.

https://www.raspberrypi.org/products/compute-module-4/?variant=raspberry-pi-cm4001000

Looks like you'd need to break the USB connector for the module out onto the RaSCSI board, but other than that, seems good to go? It's so cute it reminds me of a 1400 processor card. [:)]

 
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landoGriffin

Well-known member
Could you use the eMMC built into an RPi Compute Module as mass storage for a Mac via RaSCSI?
Definitely!! I pre-ordered my CM4 in November, but its still not here yet! The best estimate they will give me is "sometime in January, maybe".

Once I have my CM, I wouldn't be surprised if a CM version of RaSCSI comes around :-D

 

Trash80toHP_Mini

NIGHT STALKER
Very nice, I'd imagine you ordered the carrier card as well for your experimentation? You beat me to its discovery and the notion of using it this application. Can't wait to see what you come up with. [:)]

 

Trash80toHP_Mini

NIGHT STALKER
Most likely. The eMMC would take up the place of the SD connection.
Yep, that's how it works, the inexpensive models come with SD literally in the place of EMMc so you could go with one of those to kep the price down. All you loose for such a compact solution is the USB3 implementation of Pi4. Zero remains a very inexpensive solution, but CM4 puts the card @landoGriffin mentioned just about anywhere inside a Mac or onto the tiniest of external solutions, which also puts its onboard WiFi antenna outside the RFI shielding.

 

max1zzz

Well-known member
I did think about making my board using a CM4 but the lack of stock anywhere made me go for the zero, It would be nice to have the added performance of the Pi 4 for the newer powerbooks. I would be a little concerned about the Pi4's reputation for running hot though, in the confines of a PB HDD bay this might cause a issue. There is only one way to know for sure though! :)

 
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Trash80toHP_Mini

NIGHT STALKER
I was also thinking about heat, but it's made for very high performance. Can it underccocked quite a bit and still exceed requirements by far? External case would be vertical for convection. There was a very nice little case like that in the day. Connection included a SCSI passthru.

 

uyjulian

Well-known member
Yep, that's how it works, the inexpensive models come with SD literally in the place of EMMc so you could go with one of those to kep the price down. All you loose for such a compact solution is the USB3 implementation of Pi4. Zero remains a very inexpensive solution, but CM4 puts the card @landoGriffin mentioned just about anywhere inside a Mac or onto the tiniest of external solutions, which also puts its onboard WiFi antenna outside the RFI shielding.
On Pi4, USB is implemented over PCIe.

On CM4, the PCIe bus is exposed, allowing you to add USB or another interface. (PCIe<->PCI<->NuBus?)

 

Michael_b

Well-known member
Finally put mine together, seems to work very well with my Pi Zero W/SE/30. I used the Gimons baremetal fullspec build 1.50 and set up a 7.5.5 image using Basilisk II. Then I simply copied the 2GB image I made to the SD card file system, renamed it to .hds rather than .dsk, and changed the .ini config file...

seems to work perfectly, and I can now easily boot Basilisk II from the image on the SD, add programs to it, then put the SD card back in the RasPi and boot my SE/30- no need to use floppies to get programs over anymore!

 
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