Hello, I'm a decent collector of big iron, aka mini computers, mainly DEC and DG. I'm often facing common problems with storage devices, magnetic discs and tapes are a little prone to give headaches after years, and replacement drives/media in case of a severe failure are unobtainable. In some cases, the ability to make a dump of the media, also without a running computer is very important.
Whence the idea: realize an universal device, with several input/output interfaces, which could be used both as storage emulator, to run a computer without real storage, and as controller emulator, to read/write a media without a running computer. To reduce costs as much as possible, and to allow the better compatibility, the main board shall host enough electrical interfaces to support a large number of disc standard interfaces, ideally by exchanging only a personality adapter for each specific interface, i.e. connectors and few components. There are several orders of problems: - electrical signals, number and type (most disk employ 5V TTL or 3.3V TTL, some interfaces use differential mode for some faster signals?) - logical implementation: several electrical signals are used for a specific interface. These must be handled with correct timings - software implementation: the universal device shall be able to switch between interface modes and be controlled by a remote PC I suppose the only way to obtain this is to employ an FPGA for logic implementation of the interface, and a microprocessor running Linux to handle software management, data interchange to external (via Ethernet). This means a Xilinx Zynq module for instance. I know there are several ready devices based on cheaper microcontrollers, but I'm sure these can't support fast and tight timing required by hard disk interfaces (SMD-E runs at 24MHz). The main board should include a large enough array of bidirectional transceivers, possibly with variable voltage, to support as much interfaces as possible, namely at least Shugart floppy, ST506 MFM/RLL, ESDI, SMD, IDE, SCSI1, DEC DSSI, DEC RX01/02, DG6030, and so on, to give a starting point. The common factor determining what kind of disc interface can be support on hardware side is obviously the type of transceiver employed, for instance a SATA would require a differential serial channel, which could not be available. But most old electronic is based on TTL/CMOS 5V logic, so a large variety of computer generations should be doable. For the first phase, I would ask you to contribute with a list of interfaces which could be interesting to emulate, specially if these are similar to one from my list. I please submitters to send me by email or by web link when possible, detailed documentation about the interface they propose, so I can check if it could be doable and what kind of electrical signals are needed. Also detailed information about interfaced I listed is appreciated, as could give some detail I'm missing. Thanks Andrea
