SCSI to SD/IDE Phill Harvey-Smith afra at aurigae.demon.co.uk <mailto:cctalk%40classiccmp.org?Subject=Re%3A%20SCSI%20to%20SD/IDE&In-Reply- To=%3C4CFAF40D.30108%40aurigae.demon.co.uk%3E> Sat Dec 4 20:08:13 CST 2010 * Previous message: SCSI to IDE * Next message: SCSI to SD/IDE * Messages sorted by: [ date ] [ thread ] [ subject ] [ author ] ________________________________ Ok guys, The Good bit.... All this talk of SCSI to whatever got me curious so I started experementing. What I have so far : An AVR ATMega1284 (DIP40), connected to an SD card by SPI and to the SCSI bus via 4 LS chips (1xLS273 and 3xLS240). I currently have implemented just a few of the SCSI command set, Identify, read, write, test ready and request sense. Thist is enough to be able to connect to a PC SCSI card, format the drive and read and write files to it....heheh I can even boot off it ! I'm using Chan's FatFS, and in this way the drive seen by the SCSI is actually a large image file on the SD card, I did this as it will make backing up the drive *MUCH* easier if the target system is not a PC, as you can simply take the SD card out and copy the image file without worrying about it's internal structure. In theory this will also make sharing data between the target system and an emulation running on something more modern. There's a couple of pictures here : http://www.stardot.org.uk/forums/viewtopic.php?f=11&t=3646 The bad bit...... Whilst this all works it's SLOWWWW, using Norton utilities SI, reports that the disk is 0.2x the speed of an original PC, cirtainly bootup times are much more akin to what I would expect from a floppy drive :( So I would sugest that for replacing hard disks that using SCSI->SD is probably not going to be fast enough. My next experements are going to center on replacing the SD with an IDE drive, hopefully this will provide a suitable speed increse, asuming that this works it should be easy enough to use a CF->IDE adapter board to use a CF drive instead of an IDE, which will allow the media to be removable and easiliy swapable. The other thing I want this to support is 256 byte sectors as some old machines rely on this, a feature which is supported by some of the early SCSI/SASI to MFM/RLL boards but very few native SCSI drives, this would be of perticular intrest to some of the Acorn 8 bit machines. Comments & sugestions welcome. Cheers. Phill. -- Phill Harvey-Smith, Programmer, Hardware hacker, and general eccentric ! "You can twist perceptions, but reality won't budge" -- Rush. ________________________________ * Previous message: SCSI to IDE * Next message: SCSI to SD/IDE * Messages sorted by: [ date ] [ thread ] [ subject ] [ author ] ________________________________ More information about the cctalk mailing list <http://www.classiccmp.org/mailman/listinfo/cctalk> ________________________________ -----REPLY----- Huzzah! Good for you! Glad to see *something* coming out of all of this. Congratulations! Have a nice day! Andrew Lynch