MFM Drive replacement

[Keith]

Has anyone gotten a IDE or Scsi drive to work on your S-100 equipment.
I noticed Marcus had a tread asking the same question but never got a
good answer. I have been going through my MFM drives to get ready to
install one using the STDC controller. I have a couple small MFM
drives but wondered if there is a better answer. Buying these on Ebay
is a real (&*(* shoot unless you pay a arm and leg with a return
policy.
I know I would have to stay with CP/M as Cromix device drives would be
a bit much.
Tilmen Reh has a nice write up I can post if people are interested.
CF drives would be alright for CP/M as the rewrites are to bad

[Michael George Hart]

I have the Super I/O Controller, manual
That is designed to take up to 4 IDE dirves

--
I, the unwilling, was led by the unqualified, to do the unbelievable for so
long with so little, that I attempted the impossible with nothing......"

[MdntTrain]

I have IDE running on my IMSAI. No offense to Mr. Reh, but I was not
interested in the GIDE approach which I view as a kludge. So I did
some reading, and with the guidance of my friend Allison, I made my
own IDE board and CBIOS routines.

I used to have a custom S-100 case that would hold 5.25" floppies and
a hard drive, and if I still had that, I would have preferred MFM ...
just to use the vintage equip. But sans that, the IDE makes far
better sense. At least I'm using a first generation Western Digital
IDE drive.

JS

[kharrell]

Is that for sale now. I have looked and been told it wasn't. I assume
it's on your web site and has the cbios drivers?

[Michael George Hart]

I don't know if any of this is real anymore but here is the URL
http://www.imsai8080.com/

[M H Stein]

Boy, first you replace the floppies and now the hard disks...

You're taking all the fun out of running these "classics"; might as well just
run an emulator ;-)

Now, a completely transparent ST512 MFM <> IDE interface, that *would*
be nice...

mike
**************************************************************************************

----------
From: Keith[SMTP:khar...@gmail.com]
Sent: Monday, April 27, 2009 10:15 AM
To: Cromemco
Subject: MFM Drive replacement

[Michael George Hart]

Are you going to share your design?

[r...@speakeasy.net]

I have an IDE drive running on a 10 MHz Z80, BUT it is *NOT* S-100.

This is a homebrew Z80 with system memory consisting of two 32k x 8 SRAMs and a 32k x 8 EPROM that can be switched in and out of the memory map by writing to an I/O port.  It has a RAMdisk that is two 512k x 8 SRAM chips, and an IDE interface (all TTL and no PLDs).  The IDE design is from Phil Ruston (see www.retroleum.co.uk).  I have two of these things running, one is stand-alone with a Linux PC running "minicom" as the console, and the other is stuck in the drive bay of an old KayPro II that I jumped up to 5 MHz (from 2.5).  The KayPro acts as a terminal for the homebrew Z80.  The serial ports (2x) are implemented with a Zilog DART.

In experimenting with the IDE interface, I find that it is not as robust as I had hoped.  It seems to work well with some (but not all) small (older) IDE drives.  I am also running it with a CF module (2 GB) via one of those IDE to CF adapters.  That works well too, but I have found that it will not work universally with ALL CF modules.  I also experimented with an IDE to SD adapter, and got it working (at low level) with a 2GB SD card.  I had trouble with running CP/M from it.  I don't know (yet) if the problem is hardware or software (or both).

Both of these homebrew systems are running CP/M 2.2 that loads up in a flash (from EPROM).  At 10 MHz, with a RAMdisk, it is *VERY* responsive.  A: is the RAMdisk, and B: and C: are partitions on the IDE device.

It *CAN* be done.  There are a few pictures on my Web site (www.hanscom.us) under the "classic 8-bit systems" link.  There are even pictures of the "Rpro" (Kaypro II with my homebrew in the drive bay). *smile*

Roger

[Marcus Bennett]

I'll weigh back into this disastrous topic ...

What we all obviously want is a plug replaceable solid state MFM drive .  This means you'd ideally unplug the old 40MB or so spinning (but not for long) 20 year old plus drive, then plug in a a solid state  (say based on CF or SD card) replacement.

And in a nutshell this is possible from Datex with the (>1500  USD)  DWX500 emulator.  When I called them they said it was SD based and that the drive it emulated was fixed, i.e. you cant remove the underlying SD card and slot in a new one.

Datex DWX500

In other words Datex has proved that it is possible  [though I never tried it, but I did ask them if it could cope the way the STDC track formats a disk e.g.

The STDC formats the hard disk by track, not by sector. Each track is formatted
to store 10K bytes of data, as follows:
                          Bytes                 Value
Preamble                 64                    all zeros
Sync byte                1                   04
Start alignment          5                  00,AA,AA,AA,00
Header                   3                  low cylinder, high cylinder, surface
                                                  #
Data                      10,240
End alignment             4                  00,AA,AA,00
End header                3                  low cylinder, high cylinder, surface
                                                  #

CRC                       2                  varies
Syndrome                  2                  0000 (if no errors)
Postamble                 2                  0000

],  they said probably!



-------------

As an alternate tack, there are various traces of the source code for the 68000 Cromix Hard disk drivers  in the code I have acquired from Malcolm McLean. 

SMD Drivers for Z80

IOlib sources 31.05




If we could find a IDE or CF based S-100 card  (note Harte Super IO controller is no longer available) and write a (say) SMD driver equivalent, we could slot this into the Cromemco sysdef file

% Block devices:

    BDEV    01      cflop                   % Cromemco floppy driver
    BDEV    02                              % Suggested uflop
    BDEV    03      allmem                  % Amem driver (required)
    BDEV    04                              % Suggested tflop
    BDEV    05                              % Suggested ramdsk
    BDEV    06      stdc                    % STDC driver
    BDEV    07      smd 0                   % Removable part of SMD 0
    BDEV    08      hd                      % IMI hard disk

and we'd be in business as they say.

First obstacle to this plan is that I see no evidence of a currently available S-100 card able to support IDE / CF.


-----------------

So the currently flawed solution is to

a)  Buy eBay MFM drives  (freely available in the US,  but not in Europe so don't give me any hard luck stories please!) and use them on my STDC

b)  Enter the lottery every other week and if I win, well I'll buy a Datex drive or two and give it a test.

[MdntTrain]

On Apr 28, 3:23 am, Marcus Bennett <amou...@gmail.com> wrote:
> What we all obviously want is a plug replaceable solid state MFM drive.

Interesting idea, but that's not what I want. My interests are more
in keeping the older hardware going.. for example, I like hearing and
seeing 8" floppy drives and MFM hard drives working. A CF card works
but is a totally bland experience.

With minimal use and replacing capacitors, I think I'll be able to
keep my few MFM drives working for another 20 years at least,
especially the overengineered, slow-rotating earliest ones like the
ST-506 or IMI-5012H.

However, I understand that peoples' needs here vary greatly. Those
who use their systems more, are going to need more reliable
solutions. Then IDE is the only way to go... ditch the complicated
MFM controllers.

jS

[MdntTrain]

On Apr 27, 9:09 pm, Michael George Hart

> Are you going to share your design?

well, I'd love to, but two things keep me from doing that:

1. I can barely find the time to eat much less develop a website.

2. Though my IDE works flawlessly, I'm fairly certain it would be seen
as an "inelegant design" that only I find satisfying. I just don't
feel like being criticized for something that I'm happy with. The
inelegance results from chosing simplicity instead by:

a. hardware: since my system is 8-bit, I ignore upper 8 bits of 16
bit IDE interface lines.. so each sector is 256 bytes instead of 512.
This choice eliminates the complication of a latching system. Also,
while some IDE devices can perform 8-bit transfers, staying in 16-bit
mode broadens device compatibility.

b. software: Then, I found I got the best performance using only 128
bytes out of each 256 byte sector.. to avoid the whole mess of having
blocking/deblocking routines which are very time-costly. CPM is
native 128 bytes, so that's what I use.

So, with the 40MB drive I use, I therefore only have access to
10MB. Since CPM's limit's is 8MB for one drive, and I don't like
having drives over 1-2MB, these limits work perfectly for me.

jS

[Marcus Bennett]

Actually,

I do somewhat concur with your viewpoints on the older hardware.  From a purist standpoint I'd also like to keep the originals going.

But I am 99% convinced that the MFM drives will not last too much longer, even at 3600 rpm. 

For 8 " drives I have a different complaint ... they are very noisy, and here in Switzerand where it is very bad form to make  any noise after 10 pm   (including flushing a toilet by the way), well I have to power down early.

And finally, as somoebody who needs to remain pretty globally mobile, when I next country hop I am not sure I will be able to transport 6 or 7 8" drives in their cabinets.  They are enormous!

So my compromise is to keep the System Units and generally shrink the peripherals (and media).

marcus.

--
marcus bennett    amo...@gmail.com

[MdntTrain]

On Apr 28, 3:02 pm, Marcus Bennett <amou...@gmail.com> wrote:

> But I am 99% convinced that the MFM drives will not last too much longer, even at 3600 rpm.

What's your reasoning?

> here in Switzerand where it is very bad form to make  any noise after 10 pm

Even if you live by yourself in a detached house?

jS

[marcus bennett]

jS :

The reason that I determine that MFM drives are pretty doomed is
mostly my own experience ...

These 20 year old plus drives are I admin beautfully over engineered.
No glass platters here!

But I have had many cases of either

a) component failure on the electronics card - which is potentially
replaceable

b) drying out of bearings, from which I've never really sucessfully
recovered. The drive might appear to be okay for the first (say) 200
hours but after that restarts might not go too well, and higher
friction can also lead to popping of the electronics (and some nice
burning smells). If you have had experience of re-lubricating these
mechanisms I am sure a good detailed howto guide with pictures would
be appreciated by all.

Regarding Swiss quietness. Something I'm quite a big fan of : so the
10 pm curfew IMHO is respectful to observe wherever you are in
Switzerland , IMHO.

regards marcus.

[MdntTrain]

> The reason that I determine that MFM drives are pretty doomed is mostly my own experience ... I have had many cases of either

>
> a) component failure on the electronics card - which is potentially replaceable

Yeah. I try to head this off by replacing the most likely to fail --
the electrolytic caps. On all my MFMs, they've been in need of repl.

> b) drying out of bearings, from which I've never really sucessfully recovered.  

I've not spent a lot of time looking at this, but from what I recall,
the motors are very high precision, are permanently assembled, and use
sealed bearings. I've not yet been able to take one apart.


jS