Fred Cisin wrote:
On Sun, 3 Jun
2012, Chuck Guzis wrote:
Obviously, "HD" means something
different to me--500kbit/sec MFM data
rate at 360 RPM recording, versus 250kbit/sec MFM data rate at 300
RPM.
I think that he was referring to the "dual mode" drive, not the
recording,
and to the issues involved in using a "1.2M" drive from a PC, lifted from
a 5170, with a 360K diskette, to try to read and write things such as
Apple2, TRS80 model 1, Kaypro2, etc.
We have a real problem with any carelessness in the terminology!
It's inaccurate as hell, but most people will understand what I MEAN if I
say "5150 360K drive" and "5170 1.2M drive" in such cases, and
"DD" and
"HD" for the recordings, although I have NEVER been happy with saying
"quad density" for 250K-dtr, 300TPM 96tpi! And I REFUSE to call the
double sided version of THAT "SUPER DENSITY"!
Just to add some complexity (or perhaps some confusion) to the situation,
the RX50 from DEC uses DD floppy media, but if I remember correctly,
has 96 tpi. I know that on a PC, the HD drive is used to read and WRITE
the RX50 floppy media using John Wilson's program "PUTR.COM". In
addition, from within Ersatz-11, I am able to use the 5 1/4" HD drive
(in my case B: under Windows 98SE - the A: drive is 3.5" HD) as an
RX50 as well. In addition, PUTR will even perform a hardware
low level FORMAT of the RX50 media. I am not sure if this
FORMAT operation under PUTR is identical to what DEC would
produce on a Rainbow RX50 which can also FORMAT the RX50
floppy media, but in the past when I did so, they can be read and
written using a DEC RX50 under RT-11 on a DEC PDP-11/73.
The RX50 has 800 blocks on one side for a total of 409,600 bytes.
If I remember correctly, the geometry is 80 tracks with 10 sectors
per track of 512 bytes per sector. Since the density is very similar
to a DD media from the PC, DEC was able to use that media on
the RX50. But I think there are 96 tpi (which requires the HD drive
on the PC) rather than 48 tpi which is what the DD PC drive uses.
I I have any of the physical properties incorrect, I apologize. I just
wanted to add a bit more information to the mix and note that
the RX50 media can be read and written on a PC, but MUST
use the HD 5 1/4" PC drives BUT with DD media 360K diskette
media - which is what the RX50 uses on the actual DEC drives.
I do not know if what the PC HD 5 1/4" 1.2 M drive using
DD 360K diskettes produces matches exactly what the actual
DEC RX50 expects, but it does work in practice.
Jerome Fine
