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From: cs121jj@ux1.cso.uiuc.edu
Newsgroups: comp.sys.amiga.tech
Subject: Re: A PD mac emulator - summary
Message-ID: <15600005@ux1.cso.uiuc.edu>
Date: 29 Mar 90 21:13:00 GMT
References: <1818@gannet.cl.cam.ac.uk>
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Nf-ID: #R:gannet.cl.cam.ac.uk:1818:ux1.cso.uiuc.edu:15600005:000:2345
Nf-From: ux1.cso.uiuc.edu!cs121jj    Mar 29 15:13:00 1990


/* Written  6:47 am  Mar 28, 1990 by bdb@cl.cam.ac.uk in ux1.cso.uiuc.edu:comp.sys.amiga.tech */
/* ---------- "A PD mac emulator - summary" ---------- */
Do I have any way of transfering data from mac disks - like the AMAX middle
few tracks technique?

No. I initially got data across by serial transfer - of entire disk images.
Now, I plug my amiga scsi drive into a mac, and write data onto the
mac partition of it.
/* End of text from ux1.cso.uiuc.edu:comp.sys.amiga.tech */

I was wondering why one could not use this idea to read mac disks on an
Amiga drive...

Since the Mac drives have adjustible spin rates on the drive motors, that
would lead me to believe that all the circular tracks on the disk have the
same number of sectors, but are different sizes.  So why not read the far
and near tracks (the tracks that are NOT the "middle" tracks that both Mac
and Amiga can read on those AMAX-Mini-Transfer disks) by getting consecutive
sectors on consecutive passes of the drive?

By this I mean, to get sectors A-Z, first get A, any way you want to, then
wait for the disk to spin 1 complete revolution PLUS 1 sector and then read
THAT sector (sector B, as I call it in this note).  Do the same thing over
again to get sectors C-Z.  And on the longer tracks located physically on the
tracks that are greater in diameter (the previous description was for the
tracks that are the shortest in diameter) , just use the same idea, except
you may need to make more than 1 pass for each sector (since it is physically
longer, the data will be "stretched out" across the sector because each sector
can only hold X bytes of data [X= a fixed number]). 

This idea will result in slower reads on data located non-centrally, but at
least it'll save all of us not having to buy a Mac drive!  (But if we did
get a Mac drive, couldn't we use THAT drive ALL the time?  For BOTH Amiga &
Mac, since the Mac drive can adjust the speed and the Amiga drive cannot??)

Let me know if this is a good idea...if you like it and use it, give me some
credit for it, because (as far as I know), nobody but me uses this at all.

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Jeff Nicholson         jeffo@mrcnext.cso.uiuc.edu      Amiga + '030 = POWER!!!
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