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SCSI2SD, The SCSI Hard Drive Emulator for retro computing.
Traditional hard drives last 5 years*. Maybe, if you're luckly, you'll get 10
years of service from a particular drive. The lubricants wear out, the spindles
rust. SCSI2SD is a modern replacement for failed drives. It allows the use of
vintage computer hardware long after their mechanical drives fail. The use of
SD memory cards solves the problem of transferring data between the vintage
computer and a modern PC (who still has access to a working floppy drive ?)
Traditional hard drives last X years. Maybe, if you're luckly, you'll get X years of
service from a particular drive. The lubricants wear out, the spindles rust.
SCSI2SD is a modern replacement for failed drives. It allows the use ofvintage
computer hardware long after their mechanical drives fail. The use of SD memory cards
solves the problem of transferring data between the retro computer and a
modern PC (who still has access to a working floppy drive ?)
Features:
Terminator, termpwr, firmware upgradable (via the SD card)
Selectable SCSI ID (via jumpers)
Emulates a non-removable hard drive (does not present as a removable memory card reader) for maximum compatibility.
Unit attention configurability.
Technical Specifications:
SCSI Interface: SCSI-2 Narrow 8-bit 50-pin connector.
SD Card Support:
(state max size)
Currently SD standard (1GB), no SDHC/SDXC support.
Power:
Dimensions:
Performance:
Sequential read/write: 250kb/sec, 50kb/sec. Add some results of some SCSI hard drives
for comparison. 160Mb, 250Mb, 1Gb.
Compatibility:
Tested with Linux, Apple Macintosh System 7.5 on LC-II, LC-III, and LC-475 hardware.
Love to hear your success stories on other platforms.
*All statistics are made up.
Features
In-built active terminator.
Can optional supply terminator power back to the SCSI bus
Emulates a non-removable hard drive for maximum compatibility.
Firmware updatable over USB (TODO software not yet implemented)
Highly configurable over USB (TODO software not yet implemented)
Selectable SCSI ID
Selectable parity support
Enable/disable Unit Attention Condition
Artificial limits on the SCSI disk size (eg. limit size to 4G to avoid OS bugs)
Technical Specifications
SCSI Interface
SCSI-2 Narrow 8-bit 50-pin connector. Supports asynchronous transfers only.
SD Card Interface
Standard SDSC (1GB maximum size)
SDHC (32GB maximum size)
SDXC cards are untested. Donations welcome.
Communication is via the SPI protocol at 25MHz.
Power
5V via standard molex drive connector.
Dimensions
10cm x 10cm x 1.5cm
A 3D-printable bracket is in testing to suit a standard 3.5" hard disk bay.
Performance
As currently implemented:
Sequential read: 250kb/sec Sequential write: 50kb/sec
These numbers are dreadful. I am working on updating the slow polling SD card
communication to use DMA. I expect the performance to reach 1.8Mb/sec.
Compatibility
Tested with Linux (current), Apple Macintosh System 7.5.3 on LC-III, and LC-475
hardware.