XL1201 and SCSI2SD v5 128GB

I'm attempting to use the SCSI2SD v5 with a 128G microSD card.

You can find out the size of an SD card attached to a modern Mac with diskutil list and then diskutil info /dev/disk8 (or whatever device it's listed as). This microSD card is reported as:

# diskutil info /dev/disk8
   Device Identifier:        disk8
   Device Node:              /dev/disk8
   Whole:                    Yes
   Part of Whole:            disk8
   Device / Media Name:      SD  USB_3_0 Read

   Volume Name:              Not applicable (no file system)

   Mounted:                  Not applicable (no file system)

   File System:              None

   Content (IOContent):      None
   OS Can Be Installed:      No
   Media Type:               Generic
   Protocol:                 USB
   SMART Status:             Not Supported

   Total Size:               127.1 GB (127103139840 Bytes) (exactly 248248320 512-Byte-Units)
   Volume Free Space:        Not applicable (no file system)
   Device Block Size:        512 Bytes

   Read-Only Media:          No
   Read-Only Volume:         Not applicable (no file system)

   Device Location:          External
   Removable Media:          Yes
   Media Removal:            Software-Activated

   Virtual:                  No
   OS 9 Drivers:             No
   Low Level Format:         Not supported

So, the microSD has 248,248,320 sectors.

An ISO of the Genera 8.3 CD is about 636,682,240 bytes long, or 310,880 CD-ROM sectors of 2,048 bytes each or 1,243,520 SD card sectors.

I'll put the CD-ROM, for testing purposes, at sector 240,000,000. This can be done with dd if=GENERA_8_3.iso of=/dev/disk8 seek=240000000.

Now, I configured SCSI2SD with:

  • Original XL1201 Partition
    • Copied from original SD, 10,311,338 blocks of 1,280 bytes each = 13,198,512,640 bytes or about 12.3GB
    • SCSI ID: 1
    • Hard Drive
    • SD card start sector: 0
    • Sector size & count: as above
    • (Next SD start sector is 25,778,345 because SD sectors are 512 bytes)
  • Genera 8.3 CD-ROM
    • SCSI ID: 6
    • CDROM
    • SD card start sector: 240,000,000
    • Sector count: 310,880

Earlier, I had modified the *.boot files to use FEP8: so this will boot fine.

And, lo and behold, it works!

So, apparently it's perfectly fine to use SCSI2SD with 128G microSD cards.

Douglas Fields

Writing LISP and Haskell since 1990