readme.txt

   1 SCSI2SD, The SCSI Hard Drive Emulator for retro computing.
   2
   3 Traditional hard drives last 5 years*. Maybe, if you're luckly, you'll get 10
   4 years of service from a particular drive. The lubricants wear out, the spindles
   5 rust. SCSI2SD is a modern replacement for failed drives. It allows the use of
   6 vintage computer hardware long after their mechanical drives fail. The use of
   7 SD memory cards solves the problem of transferring data between the vintage
   8 computer and a modern PC (who still has access to a working floppy drive ?)
   9
  10 *All statistics are made up.
  11
  12
  13 Features
  14
  15     In-built active terminator.
  16     Can optional supply terminator power back to the SCSI bus
  17     Emulates a non-removable hard drive for maximum compatibility.
  18     Firmware updatable over USB (TODO software not yet implemented)
  19     Highly configurable over USB (TODO software not yet implemented)
  20         Selectable SCSI ID
  21         Selectable parity support
  22         Enable/disable Unit Attention Condition
  23         Artificial limits on the SCSI disk size (eg. limit size to 4G to avoid OS bugs)
  24
  25
  26 Technical Specifications
  27
  28 SCSI Interface
  29         SCSI-2 Narrow 8-bit 50-pin connector. Supports asynchronous transfers only.
  30 SD Card Interface
  31         Standard SDSC (1GB maximum size)
  32         SDHC (32GB maximum size)
  33         SDXC cards are untested. Donations welcome.
  34         Communication is via the SPI protocol at 25MHz.
  35 Power
  36         5V via standard molex drive connector.
  37 Dimensions
  38         10cm x 10cm x 1.5cm
  39         A 3D-printable bracket is in testing to suit a standard 3.5" hard disk bay.
  40
  41
  42 Performance
  43
  44 As currently implemented:
  45
  46 Sequential read: 424kb/sec Sequential write: 414kb/sec
  47
  48 Tested with a 16GB class 10 SD card, via the commands:
  49
  50  # WRITE TEST
  51  sudo dd bs=8192 count=100 if=/dev/zero of=/dev/sdX oflag=dsync
  52
  53  # READ TEST
  54  sudo dd bs=8192 count=100 if=/dev/sdX of=/dev/null
  55
  56 I am working on updating the SD card communication to use DMA, to allow simultaneous use of the SD and SCSI interfaces. I expect the performance to reach 1Mb/sec.
  57
  58
  59 Compatibility
  60
  61 Tested with Linux (current), Apple Macintosh System 7.5.3 on LC-III, and LC-475
  62 hardware.
  63