Possible PUTR bug?

allison allisonportable at gmail.com
Sat May 11 18:50:05 CDT 2019

My Solution is easier, least for me.

I have a few Z80 CP/M machines with 765A in it and if it can't read it
its likely due to being hard sectored or M2FM.  I has 3.6, 5.25 and 8"
and  the 5.25 are Teac FD55gfh which are dual speed and can do all
modes. With my own software and utilities it does whatever even RX180,
RX50, RX33, and RX22/23 formats from the DEC pool.

The PC machine for when that stuff is needed is a DELL pizza box that
has 32mb of ram and 486dx/66 (ISA/ISA16) and can run dos though NT4 as
needed as I have a buttload of ST3660As as media for them (have two as a
spare).  That machine uses a combo IO controller for the FDC seems to do
what I ask of it.  Also an old Compag with similar features and PII and
32MB and also does Ethernet but the disk controller is a newer ISA16
using a combo chip and most of the combo chips after late 90s-ish seem
to have an even shorter VFO sync window (flash blindess).

I neither expect nor desire modern machine with anything past NT4 to
behave well with old disks.  Though Mini-ITX boards all seem to support
everything and anything and have all the legacy ports.  They all run
linux and if needed a partition (60mb of disk is trivial) for MSdos
6.22 or freedos.

Oh, unless its under threat the OS is linux, freedos, or if required XP
Though the latter is usually under VMware or Virtualbox on Linux..  I
just got tired of all the winders hassles and requirements for insane
hardware needs every few years.  Most stuff runs fine under dosemu or wine.

As to RT11, I have run mostly V5.0x and as needed if a device required
it a later driver borrowed from V5.04 or later.  It just seems to work
with out much pain.

As to running a RX50 on a PC...  That drive was a neat thing but its
mostly the interface is incompatible with most standard floppies and
a FD55A/B or any of the 48tpi 40 track drives will read and write the
media.  I make a point of only using it on PDP-11 as transfer media,
its low density so its marginal for much.  Keep in mine that drive
select is used to select the A or B drive of a RX50 there is no side.
They had a terrible track record for reliability.  I can put Two RX33
[teac fd55gfh] in the same space and store more.  Some to think of it
most Late PC 5.25 and 3.5 inch drives are incompatable with old standard
[TM100 and that era] as many do not have a 1 of 4 drive select jumper
and use the funky PC only twist cable.

I neatly sidestep all of the cruft and hacks needed for super wizbang
winXP and later machines.  I figure if I'm going to play with old
hardware I need to retain the old hardware to maintain them.  So I
retained the best of the best old PCs as they bulk of them are crap.
I buy new hardware that is not neutered.  Mini/Micro-ITX board with
atom or celeron CPUs (really all that's needed) are cheap and easily
built up into linux boxes or if you must any of the older 32 bit
winders incantations.


]On 05/11/2019 11:22 AM, Douglas Taylor via cctech wrote:
> I understand your frustration, because all I really wanted to do was
> read/write RX33 and RX50 5-1/4" floppies to move data in and out of my
> microPDP11.  Once, I wanted to write an RX23 3-1/2" floppy with OpenVMS
> PAK files that could be read on an DEC Alpha.
> 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 dedicated a DELL XPS 233H to this task, 32MB memory, Pentium II cpu. 
> Boots from 3GB hard disk, DOS and Win 3.1 (if you so need it).  I also
> have an IDE to CF card adapter standing by when the hard disk dies. 
> Love to have something with a smaller form factor, but it gets the job
> done.
> Doug
> On 5/11/2019 10:35 AM, Charles via cctalk wrote:
>> Just an update... I spent an entire long afternoon wrestling with that
>> old PC, trying to find some combination of HDD jumpers and BIOS
>> settings that would allow the XP hard drive to boot with another drive
>> attached (either on the slave connector or the secondary channel with
>> the CD-ROM removed). No dice.
>> So I had the bright idea to use Minitool's Partition Wizard, and
>> shrink my Windows partition so there'd be room for a  newDOS partition.
>> But it won't even run (probably because I have only 64 MB RAM on that
>> box). Grrr. It's unbelievably slow anyhow, so more SDRAM on order,
>> which is really cheap these days.
>> I'd get a newer PC for the workbench, but need to keep the old
>> motherboard because there are a couple of devices (including a PB-10
>> PROM programmer) which are ISA slots.
>> So, this has become a Windows/PC (ugh) project instead of just being
>> able to play with my PDP-11...

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