5 Mar
2007
5 Mar
'07
2:03 p.m.
The 300k data
rate tells me that you recorded this on a
1.2M HD drive - I'm assuming you did not specify a 300-250k
data rate translation when you recorded it (?)
It's not 300 data rate it's 250! Also make sure the PC is trying to run the 1.2mb drive
at 300rpm
and NOT 360 or switching to 300kbs while using the nominal 360rpm
as NEITHER WILL WORK. RX50 is NOT 1.2mb mode its a 80track flavor
of DD (400k per disk single sided). This is a foreign format
and requires forcing the PC hardware in many cases. I cheat
I use a FD55E (96tpi, single sided 360rpm only) as then the PC
cannot force 300 rpm.
300k does not mean HD:
300 rpm & 250kbps = DD (or SD if MGM encoding)
360 rpm & 300kbps = DD (same bit density)
360 rpm & 500kbps = HD 1.2M PC format
300 rpm & 500kbps = HD 1.44M PC format
Most PC 5.25" HD drives do not do 300rpm - they always run
360rpm and the controller uses 300kbps data rate. If it were
HD it would be 500kbps.
ImageDisk does not know or care what kind of drive is attached,
and when analyzing the disk, it has no preconcieved notion of
what it should be seeing - it scans all available densities and
data rates and determines what it can read - that is why ImageDisk
files do NOT have an indication of "drive type" - ImageDisk doesn't
know about drives - only what it can see and manipulate at the
controller (as noted in a previous email, I an considering changing
this as it confuses some people, but at the moment, ImageDisk does
not think in terms of "drives" - it thinks in terms of density and
data rate).
When reading 96tpi DD disks, I use a Teac-55F which is a 300rpm
DSDD drive. This gives me the native 250k date rate the way god
intended :-)
In DEC parlance RX50 refers to 80tracks, 96tpi, single
sided
with 10 sectors per track and 512bytes persector formatted
at a data rate of 250kbs @360 rpm. It also refers to the drive
known as RX50.
Sorry, but that doesn't make sense - 10x512 DD format is done
at 250kbps / 300rpm - standard double-density. PeeCee HD drives
will do it at 300kbps / 360rpm. I am not aware of any DD formats
that use 250kbps / 360rpm, Although ImageDisk should handle this
if the drive can ... (Chuck?)
Dave
--
dave06a (at) Dave Dunfield
dunfield (dot) Firmware development services & tools: www.dunfield.com
com Collector of vintage computing equipment:
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