11 May
2019
11 May
'19
9:04 a.m.
On 5/11/19 8:22 AM, Douglas Taylor via cctalk wrote:
Finding a PC that supports the 5-1/4" floppy
drive is difficult, the
BIOS or FDC chips only support 3-1/2" floppies in many late model PC's.?
It appeared only a few of the older PC's that supported the 5-1/4"
drives could actually change the spindle speed so you could read/write
RX50 format.
I have to admit that I don't follow this one. Although I'll admit the
possibility that some odd chipset doesn't support the 300Kbps data rate
needed to use normal "360K" floppies in a 5.25" HD drive spinning at 360
RPM, I've yet to run across one. Finding a modern PC with legacy floppy
support is a different issue. Either using a 5.25" DD-only drive (such
as a Teac FD55F) or jumpering a 5.25" HD drive to use 300 RPM are both
options. From the standpoint of the hardware, there's no difference
between a "720K" 3.5" drive and a 5.25" one so configured.
In the case of RX50 on the PC, it doesn't matter. The format is 10
sectors of 512 bytes, which isn't supported by the PC BIOS in any
regular sense (9 sectors is the norm). So most packages that deal with
FILES-11 RX50 floppies on a PC use direct hardware (chip) access and
bypass the BIOS completely. PUTR is one such package.
The real issue is that the need for *writing* RX50 FILES-11 format
diskettes is virtually non-existent. With the exception of PUTR, the
packages that I've seen (dating from 1984) are all for *reading* them.
Heck, I've written a couple myself, including one for CP/M-80.
--Chuck