Path: utzoo!attcan!uunet!midway!ncar!zaphod.mps.ohio-state.edu!wuarchive!psuvax1!rutgers!ub.d.umn.edu!cs.umn.edu!ux.acs!snewton
From: snewton@ux.acs.umn.edu (steven robert newton)
Newsgroups: comp.os.minix
Subject: Re: dd can't read my 1.2M drive
Summary: BootBlock Param Table+help with ST11 xt-wini
Message-ID: <2568@ux.acs.umn.edu>
Date: 26 Oct 90 08:20:34 GMT
References: <31333@netnews.upenn.edu>
Reply-To: snewton@ux.acs.umn.edu (steven robert newton)
Organization: University of Minnesota, ACSS
Lines: 29

It seems the early decision to have the driver assume a standard format
for a block disk driver (aka: /Single_sidedDisk /sd0 /Dbl_sidedDisk /dd0)
is very good for `tar cf /dev/dd0` but lousy for 85 tracks&11 sectors.

I like the idea (posted earlier) to have /dev/fd? sense the dos disk table
for #blocks and #sectors/track. (#tracks can be computed).
The big deal is that ALL BIOS's could then continue to support 3.5 or at 
disks with a block-zero read that all drives should be able to do.

Requirements: Just write boot block code with a 
jump +x1c ;around this important disk param. table
.db 22    ;a int 41h and device driver Disk Parameter Table Reference
	  ;can document all the needed fields.
.text	  ;begin your code.(Stop using x1fe for #img-size for std xaa55 sig!!)

When I had only a Tandy 2000(argh) I noticed it used the boot-param-tbl
to decide to double step a 80 track(720k) drive to read/write a 360K disk.
So, I moved the code +x27 within the bootblock and changed the block move
source to point the the new starting byte spot.
(I know it's obscure..  I could only work with debug )

I did all this--I still could handle patching all the hardware port changes.
Next I bought a Sanyo 675 xt and installed a Seagate ST124 (616cly 20Mb HD)
with a Seagate ST11(mfm 8 bit) card.
I get fs panics--it fails to rw-block(0 even!)

Should I get a ESDI SCSI or RLL conroller with my next computer??

Thanks for MINIX and all your work in improving it!!!