As an alternative to SCSI2SD devices for usage as a virtual HDD (which are costly at USD $55-$125 depending on kit options), apparently there is a cheaper, more available DIY solution out there to use a Raspberry Pi as a SCSI device emulator, called RaSCSI.
The RaSCSI software is FOSS and available as both a Raspbian Stretch tarball package (
https://translate.googleusercontent.com/translate_c?depth=1&hl=en&prev=search&rurl=translate.google.com&sl=ja&sp=nmt4&u=http://retropc.net/gimons/rascsi/index.html&xid=17259,15700022,15700186,15700191,15700256,15700259,15700262,15700265,15700271,15700283&usg=ALkJrhhwWnvTM5zBDZjaxIaCB3MA8cqC6A) or as a "bare-metal" (
https://translate.googleusercontent.com/translate_c?depth=1&hl=en&prev=search&rurl=translate.google.com&sl=ja&sp=nmt4&u=http://retropc.net/gimons/rascsi_bm/index.html&xid=17259,15700022,15700186,15700191,15700256,15700259,15700262,15700265,15700271,15700283&usg=ALkJrhjOl-sCY25wJoGcrsETQuaJUvPxfQ) (OS-less direct-boot) RPi firmware image. The FOSS hardware consists of either directly wiring up certain GPIO pins to a SCSI port (not recommended) or using a simple conversion circuit with some ICs and resistor packs from the GPIO pins to a SCSI port (recommended, since it is electrically safer and correctly converts between the different TTL levels between both the GPIO and SCSI pins). The hardware can either be DIY, or as various RaSCSI kits available online.
Unfortunately, most of the RaSCSI kits online use High-Density SCSI ports, but there is a 68kmla forum user who has created a design (
https://github.com/fran-cap/RASCSI-68kmlaver) that uses low-density IDC50 SCSI ports (as found on the NeXT computers, 68kmla forum thread (
https://68kmla.org/forums/index.php?/topic/30399-rascsi-development-thread/&)). RaSCSI also provides some X68k drivers for additional features (currently only available as drivers for those types of machines, since RaSCSI was originally intended for X68k usage).
On the software-side, RaSCSI can do the following:
- Emulate virtual SCSI disc drives
- SCSI Hard Disk images
- HDA extension - Genuine APPLE hard disk emulation (Macintosh)
- HDN extension - NEC PC-9801-55 HD emulation
- HDI/NHD extensions - HD images from PC98 Annex86 and T98Next, respectively.
- Any Linux DD image following the spec and with proper file extension
- SASI Hard Disk images (HDF extension)
- SCSI Magneto-Optical disk images (MOS extension)
- SCSI CD-ROM images (standard ISO extension)
- Initiator mode
- Controlling (host side) SCSI devices can be used.
- Allows applications such as dumping and restoring physically connected SCSI hard disks.
- Conversion board needs the direct connection or initiator mode implemented.
- X68000-only RaSCSI features
- Ethernet communication
- Ethernet driver provided by RaSCSI on the X68000 side
- Communication using the TAP device (virtual network I/F) becomes possible through the bridge device on the RPI side.
- Driver on the X68000 side can be replaced with the Neptune-X driver.
- Remote drive
- Remote file system driver provided by RaSCSI on the X68000 side
- RPI file system can be recognized as a drive as it is through the bridge device on the RPI side.
Other than sharing this info of a DIY alternative to SCSI2SD with the NeXT community, my question is has anyone tried RaSCSI before on a NeXT computer as a bootable HDD image succesfully?
Sorry I missed this thread when it was posted. I've been looking into this recently as I have some experience with the Raspberry Pi. I'd like to set up the bare metal version on a Pi Zero, but I haven't found a place where I can purchase the PC board yet. I looked through the thread at the 68kmla forums, but the last post in the thread (
https://68kmla.org/forums/index.php?/topic/30399-rascsi-development-thread/&page=5&tab=comments#comment-618621) indicates that the design has some of the pins swapped. I don't have any experience with PC board design software but I may give it a try and see if I can come up with a board that follows the original design without requiring an adapter board. It would be interesting to see one of these emulate a NeXT MO drive.
Man, RaSCSI looks really cool... too bad the boards are no longer available.
It looks like the RaSCSI thread over at 68kmla (
https://68kmla.org/forums/index.php?app=forums&module=forums&controller=topic&id=30399&page=5&tab=comments#comment-643396) has picked up again. There's also a new GitHub repository (
https://github.com/akuker/RASCSI). They're making good progress, can't wait to see the finished product.
Here is my Kicad Projects of a SCSI bus emulator PCB. Smaller PCB size with Rasp-Pi Zero.
Gerbers, BOMs available but you would need build your own board yourself.
https://github.com/novi/scsiemu-pcb