mjp@spice.cs.cmu.edu (Michael Portuesi) (12/18/86)
Keywords: Does anybody know whether the Amiga disk controller can be made to read (and write) other formats besides Amiga's? In particular, the thought of writing a utility to copy files from Amiga to Mac disks and vice-versa interests me. Please keep in mind that the Mac disk drives are variable-speed. Therefore, one would have to be able to control the speed on the Amiga drive to write things a Mac would understand. The Hardware Manual seems very vague on this topic. I do know that if I connect a 5 1/4" drive to my machine I can read Apple II disks (big deal). I know it's impossible to do things from the Mac end because the MacPlus disk drive controls the speed of the disk itself...the system software cannot control it (unlike the orginal Mac and Mac 512K machines). Not that I wanted to write the software for the Mac anyway, but the variable speed certainly poses a problem in accessing data from the Amiga end. Another problem is that Apple itself is reluctant to divulge the details on how its drive works in the first place. The documentation for their file system refers to everything in "logical blocks" and doesn't say where things are physically located on a 3 1/2" disk (which makes sense, since the filesystem should work the same regardless of media and it shouldn't make any difference to an application programmer anyway) I just want to know if this is technically feasible before I start sticking my nose in a bunch of Mac documentation. -- +----------------------------------------------------------------------------+ | Mike Portuesi | | Carnegie-Mellon University Computer Science Department | | | | ARPA: mjp@spice.cs.cmu.edu | | UUCP: {harvard | seismo | ucbvax | decwrl}!spice.cs.cmu.edu!mjp | | | | "Talking about music is like dancing about architecture" | | --Laurie Anderson, "Home of the Brave" | +----------------------------------------------------------------------------+
dillon@CORY.BERKELEY.EDU (Matt Dillon) (12/18/86)
The trackdisk driver will support raw reads and raw writes (no MFM decoding/encoding layer) on tracks. I have never tried to read a MAC disk, however, and the MAC's variable speed may cause mucho problems. On the same topic, does anybody know the RLL encoding scheme is viable on floppies? I have yet to get my hands on RLL documentation, but I've heard it can be implemented on drives which support MFM encoding. -Matt
cmcmanis@sun.uucp (Chuck McManis) (12/18/86)
Yes, you can read foreign formats, but there are a couple of conditions
to be met. First, the drive must be constant speed, since there is
no way to change the speed of the Amiga drives (except with a screw
driver) and I am pretty sure the PLL loop circuit on the floppy is
only expecting a 250K Hz clock rate. I believe the new Mac+ floppies
(800K) are constant speed but I may be wrong on this. You can certainly
read PC/DOS or CP/M format disks. The trick is to use the trackdisk
device in RAW mode, so that the entire track is read in and left
unprocessed. You can then interpret the data any way you want. If
you are really ambitious you could write a foreign format 'handler'
in which case the system would treat the disk as though it were a
native format.
--
--Chuck McManis
uucp: {anywhere}!sun!cmcmanis BIX: cmcmanis ARPAnet: cmcmanis@sun.com
These opinions are my own and no one elses, but you knew that didn't you.news@cit-vax.Caltech.Edu (Usenet netnews) (12/19/86)
Organization : California Institute of Technology Keywords: RLL From: tim@tomcat.Caltech.Edu (Tim Kay) Path: tomcat!tim dillon@CORY.BERKELEY.EDU (Matt Dillon) writes: > > On the same topic, does anybody know the RLL encoding scheme is >viable on floppies? I have yet to get my hands on RLL documentation, but >I've heard it can be implemented on drives which support MFM encoding. There are several new cards for the IBM PC that support RLL on many of the drives that are now used with MFM. However, the new RLL cards won't even work with the standard 10 Mbyte XT drives. It has something to do with requiring thin-film plating, or something else technical. Therefore, I doubt it will work on floppies. Secondly, is 800K --> 1200K all that significant? Also consider that RLL often slows disk access down? All of my (vague) information comes from reading reviews in PC, PC World, etc. Timothy L. Kay tim@csvax.caltech.edu Department of Computer Science Caltech, 256-80 Pasadena, CA 91125
phillip@cbmvax.cbm.UUCP (Phillip Lindsay) (12/19/86)
> Summary: Yes, you can read foreign formats > read PC/DOS or CP/M format disks. The trick is to use the trackdisk > device in RAW mode, so that the entire track is read in and left > --Chuck McManis > uucp: {anywhere}!sun!cmcmanis BIX: cmcmanis ARPAnet: cmcmanis@sun.com > These opinions are my own and no one elses, but you knew that didn't you. One problem people run into using the trackdisk.device to RAW-READ with INDEX-MARK (like reading IBM format disks) is the fact that the device driver interface routines (ie. DoIO(), SendIO()) clear the flag that tells the device to read with the index mark. The solution is to use the direct entry point to the device "BeginIO()." ============================================================================== Phillip Lindsay - Commodore Business Machines - Amiga Technical Support UUCP: {ihnp4|seismo|caip}!cbmvax!phillip - Phone: (215) 431-9180 No warranty is implied or otherwise given in the form of suggestion or example. Any opinions found here are of my making. /* eof */
lachac@topaz.RUTGERS.EDU (Gerard Lachac) (12/20/86)
In article <1374@cit-vax.Caltech.Edu> tim@tomcat.caltech.edu (Tim Kay) writes: >Secondly, is 800K --> 1200K all that significant? Also consider that >RLL often slows disk access down? Well, my math tells me that 800/2 = 400 800 + 400 = 1200 That's a gain of 1/2 a floppy. Pretty significant if you consider that this enables you to fit lots of things on one disk. Like Kickstart and Workbench :-) ---------------------------------------------------------------------------- "Isn't fun the best thing to have?" lachac@topaz.rutgers.edu
blgardne@esunix.UUCP (Blaine Gardner) (12/20/86)
For some good info on the subject of Apple 3.5" drives, check this
month's issue of Call-A.P.P.L.E.
--
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Blaine Gardner @ Evans & Sutherland
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