22 Oct
2025
22 Oct
'25
4:04 p.m.
I just purchased an old Gimix computer (now if only I can get it from
Orlando to Chicago before my friend goes down there for Christmas).
It has an OMTI 20C-1 MFM hard disk controller with a IMI 5018 19MB hard
disk drive in it.
I am thinking of trying to upgrade the hard drive. The Gimix System
that I worked on had a half high 20MB drive and a Syquest removable 5MB
drive.
Does anyone have an old MFM drive laying around (half high or full
height but larger than 18MB) and/or an MFM removable cartridge drive
with cartridges?
I am also going to try to rebuild a Vector Graphic Dual Store Dual 8"
drive enclosure that I picked up at VCFMW. It suffered some dampness
damage and I'm not sure the drives will come up. If you have a dual 8"
drive setup (double sided drives, and enclosure) that you need a good
home for, please let me know.
I'm in the Chicago Area.
Thanks,
Mike
bitwiz(a)12bitsbest.com
23 Oct
23 Oct
1:25 a.m.
I probably have 10 MFM drives, I don't expect any to run. I took one apart,
It had crud on the platter from the air bleed filter.
Smallest I have maybe a couple 20 Mb, Classic seagate ST220?, up to a 100
MB maxtor XT1105. I have time to test and all the old toolds,
I'll give it a try, I need to dig out a old PC, Goodwill was good to me in
the early 2000's
I was stupid and passed on a datapoint 2200, No where to store. Also a old
hammond organ, Classic. and cringe.
Probably after Christmas, Might want to consider an alternative.
Just got a new toy (hantek 2d10) scope that is not working right, Op
malfunction? . Rigol was pissing me off.
Fortunately, Got two, one for a gift, So, a reference or another turd.
Was anything MFM or RLL with a removible cart build in the 80's-90's?
I never heard of such a thing, Carts were scsi early 90's Syquest and
others?...
On Wed, Oct 22, 2025 at 4:18 PM Mike Katz via cctalk <cctalk(a)classiccmp.org>
wrote:
I just purchased an old Gimix computer (now if only I
can get it from
Orlando to Chicago before my friend goes down there for Christmas).
It has an OMTI 20C-1 MFM hard disk controller with a IMI 5018 19MB hard
disk drive in it.
I am thinking of trying to upgrade the hard drive. The Gimix System
that I worked on had a half high 20MB drive and a Syquest removable 5MB
drive.
Does anyone have an old MFM drive laying around (half high or full
height but larger than 18MB) and/or an MFM removable cartridge drive
with cartridges?
I am also going to try to rebuild a Vector Graphic Dual Store Dual 8"
drive enclosure that I picked up at VCFMW. It suffered some dampness
damage and I'm not sure the drives will come up. If you have a dual 8"
drive setup (double sided drives, and enclosure) that you need a good
home for, please let me know.
I'm in the Chicago Area.
Thanks,
Mike
bitwiz(a)12bitsbest.com
4:27 p.m.
Wow. I still run maxtor rd54 drives on one of my 11s and rd53s on the pro 380s. Work fine
enough
Gesswins device is outstanding, I have one and have used it to make backup images of all
sorts of systems.
I should probably update my code.....
On October 23, 2025 4:25:04 AM EDT, Jim Davis via cctalk <cctalk(a)classiccmp.org>
wrote:
I probably have 10 MFM drives, I don't expect any
to run. I took one apart,
It had crud on the platter from the air bleed filter.
Smallest I have maybe a couple 20 Mb, Classic seagate ST220?, up to a 100
MB maxtor XT1105. I have time to test and all the old toolds,
I'll give it a try, I need to dig out a old PC, Goodwill was good to me in
the early 2000's
I was stupid and passed on a datapoint 2200, No where to store. Also a old
hammond organ, Classic. and cringe.
Probably after Christmas, Might want to consider an alternative.
Just got a new toy (hantek 2d10) scope that is not working right, Op
malfunction? . Rigol was pissing me off.
Fortunately, Got two, one for a gift, So, a reference or another turd.
Was anything MFM or RLL with a removible cart build in the 80's-90's?
I never heard of such a thing, Carts were scsi early 90's Syquest and
others?...
On Wed, Oct 22, 2025 at 4:18 PM Mike Katz via cctalk <cctalk(a)classiccmp.org>
wrote:
> I just purchased an old Gimix computer (now if only I can get it from
> Orlando to Chicago before my friend goes down there for Christmas).
>
> It has an OMTI 20C-1 MFM hard disk controller with a IMI 5018 19MB hard
> disk drive in it.
>
> I am thinking of trying to upgrade the hard drive. The Gimix System
> that I worked on had a half high 20MB drive and a Syquest removable 5MB
> drive.
>
> Does anyone have an old MFM drive laying around (half high or full
> height but larger than 18MB) and/or an MFM removable cartridge drive
> with cartridges?
>
> I am also going to try to rebuild a Vector Graphic Dual Store Dual 8"
> drive enclosure that I picked up at VCFMW. It suffered some dampness
> damage and I'm not sure the drives will come up. If you have a dual 8"
> drive setup (double sided drives, and enclosure) that you need a good
> home for, please let me know.
>
> I'm in the Chicago Area.
>
> Thanks,
>
> Mike
> bitwiz(a)12bitsbest.com
>
>
>
4:36 p.m.
On Oct 23, 2025, at 7:27 PM, Christopher Zach via
cctalk <cctalk(a)classiccmp.org> wrote:
Wow. I still run maxtor rd54 drives on one of my 11s and rd53s on the pro 380s. Work fine
enough
Gesswins device is outstanding, I have one and have used it to make backup images of all
sorts of systems.
My Pro has one also. Among other things, it allowed me to debug a low level formatting
utility without having to worry about destroying the few drives I own. And it let me
experiment with alternate formatting settings (different interleaving) which to my great
surprise showed that the default is also best, independent of CPU speed. (Which means
that the controller is the problem and is pathetically slow.)
paul
5:31 p.m.
Yeah the Pro controller is far more hopeless than even an RQDX1. The
single biggest reason I want to get POS/M+ running with split I/D is so
I can finally have cache. A Pro with 3mb memory with cache would be
pretty impressive.
Cache makes the difference. My crummy 11/73 with the RQDX3 can run close
in speed to the 11/83 with the MTI ESDI controller when I load it with
cache.
But for MFM Dave's controller is the thing to have.
On 10/23/2025 7:36 PM, Paul Koning wrote:
On Oct 23, 2025, at 7:27 PM, Christopher Zach via
cctalk <cctalk(a)classiccmp.org> wrote:
Wow. I still run maxtor rd54 drives on one of my 11s and rd53s on the pro 380s. Work fine
enough
Gesswins device is outstanding, I have one and have used it to make backup images of all
sorts of systems.
My Pro has one also. Among other things, it allowed me to debug a low level formatting
utility without having to worry about destroying the few drives I own. And it let me
experiment with alternate formatting settings (different interleaving) which to my great
surprise showed that the default is also best, independent of CPU speed. (Which means
that the controller is the problem and is pathetically slow.)
paul
6:22 p.m.
Yeah the Pro controller is far more hopeless than even
an RQDX1. The single
biggest reason I want to get POS/M+ running with split I/D is so I can finally
have cache. A Pro with 3mb memory with cache would be pretty impressive.
How might cache be added to the Pro 380? Venix V2.0 is split I/D and cache
should work great with that too.
--
------------------------------------ personal: http://www.cameronkaiser.com/ --
Cameron Kaiser * Floodgap Systems * www.floodgap.com * ckaiser(a)floodgap.com
-- When in doubt, take a pawn. -- Mission: Impossible ("Crack-Up") ------------
24 Oct
24 Oct
5 a.m.
OS level caching of disk devices is a gennable option in M+ with split I/D.
It's actually pretty impressive; the system can do read-aheads, and also
writes can be deferred (which makes turning off the system hot very
bad). I think it can also cache the directory entry table and even a
small cache of 256kb or so makes a nice performance difference.
On 10/23/2025 9:22 PM, Cameron Kaiser via cctalk wrote:
Yeah the Pro controller is far more hopeless than
even an RQDX1. The single
biggest reason I want to get POS/M+ running with split I/D is so I can finally
have cache. A Pro with 3mb memory with cache would be pretty impressive.
How might cache be added to the Pro 380? Venix V2.0 is split I/D and cache
should work great with that too.
6:33 a.m.
On Oct 24, 2025, at 8:00 AM, cz via cctalk
<cctalk(a)classiccmp.org> wrote:
OS level caching of disk devices is a gennable option in M+ with split I/D.
It's actually pretty impressive; the system can do read-aheads, and also writes can
be deferred (which makes turning off the system hot very bad). I think it can also cache
the directory entry table and even a small cache of 256kb or so makes a nice performance
difference.
It's also a standard feature in RSTS/E, which can allocate up to 496 kW to the storage
cache (plus additional memory, if you want, for a ramdisk). I haven't tried to see
what the performance numbers look like with and without, that would be an interesting
experiment.
paul
10:43 a.m.
On 2025-10-24 7:33 a.m., Paul Koning via cctalk wrote:
I really wonder how much swapping of memory with disc is done internally
or how many buffers it has for files?
Time sharing was created for use
with 110 baud TTY's, so the first bench mark needs to be at that speed.
Ben.
On Oct 24, 2025, at 8:00 AM, cz via cctalk
<cctalk(a)classiccmp.org> wrote:
OS level caching of disk devices is a gennable option in M+ with split I/D.
It's actually pretty impressive; the system can do read-aheads, and also writes can
be deferred (which makes turning off the system hot very bad). I think it can also cache
the directory entry table and even a small cache of 256kb or so makes a nice performance
difference.
It's also a standard feature in RSTS/E, which can allocate up to 496 kW to the
storage cache (plus additional memory, if you want, for a ramdisk). I haven't tried
to see what the performance numbers look like with and without, that would be an
interesting experiment.
paul
25 Oct
25 Oct
12:14 p.m.
On Oct 24, 2025, at 1:43 PM, ben via cctalk
<cctalk(a)classiccmp.org> wrote:
On 2025-10-24 7:33 a.m., Paul Koning via cctalk wrote:
I really wonder how much swapping of memory with disc is done internally or
how many buffers it has for files?
Time sharing was created for use
with 110 baud TTY's, so the first bench mark needs to be at that speed.
Yes, RSTS-11 in 1973 would likely have ASR33 terminals. Certainly our college system did,
on an 11/20 with 16 terminal lines. But when it was upgraded to RSTS/E on an 11/45 with
better interfaces (a DH11 instead of 16 KL11 or DL11 cards) its terminals moved to 300
baud or better.
The RSTS systems at DEC had 9600 baud terminals throughout, on 11/70 machines typically.
I don't remember how many lines; 32 seems likely if not more. With 4 MW of memory
there wasn't that much need for swapping, even after subtracting out up to 496 kW for
cache. Perhaps less was used; as I recall RSTS would do file data caching only for files
tagged for caching, which on development systems would not be usual practice.
paul
On Oct
24, 2025, at 8:00 AM, cz via cctalk <cctalk(a)classiccmp.org> wrote:
OS level caching of disk devices is a gennable option in M+ with split I/D.
It's actually pretty impressive; the system can do read-aheads, and also writes can
be deferred (which makes turning off the system hot very bad). I think it can also cache
the directory entry table and even a small cache of 256kb or so makes a nice performance
difference.
It's also a standard feature in RSTS/E, which can allocate up to
496 kW to the storage cache (plus additional memory, if you want, for a ramdisk). I
haven't tried to see what the performance numbers look like with and without, that
would be an interesting experiment.
paul
24 Oct
24 Oct
1:23 p.m.
OS level caching of disk devices is a gennable option
in M+ with split I/D.
Oh, *disk* caching! Sorry, I read that as *processor* cache. That makes sense.
--
------------------------------------ personal: http://www.cameronkaiser.com/ --
Cameron Kaiser * Floodgap Systems * www.floodgap.com * ckaiser(a)floodgap.com
-- "I adore my Commodore 64" --------------------------------------------------
3:14 p.m.
On 2025-10-24 2:23 p.m., Cameron Kaiser via cctalk wrote:
That did seem to speed things up too,as well.
-----
From the PDP-11 FAQ.
Fastest PDP-8
Trivia item: did you note anywhere that the 11/60 was used to implement
the world's fastest PDP-8? The 8 support group for years used an 11/60
RSTS system down the hall, running custom microcode addons to implement
a high speed PDP8 emulator.
Rumour has it that some hacker also did this on a VAX-11/780, which
would definitely out-run the 11/60 version.
-----
I wonder if the custom microcode is still around?
Ben.
OS level caching of disk devices is a gennable
option in M+ with split I/D.
Oh, *disk* caching! Sorry, I read that as *processor* cache. That makes sense.
6:19 p.m.
Well if you know how to write microcode on an 11/60 or an 11/780 you can
probably build a pdp8 instruction set without too much difficulty. I
would wonder if a 780 would be that much faster as both systems were TTL
and the 32 bit word size is not going to be too much different.
One might have better luck writing a pdp8 on the WD WCS-11 memory space.
But that would probably still be a slug.
C
That did seem to speed things up too,as well.
-----
From the PDP-11 FAQ.
Fastest PDP-8
Trivia item: did you note anywhere that the 11/60 was used to implement
the world's fastest PDP-8? The 8 support group for years used an 11/60
RSTS system down the hall, running custom microcode addons to implement
a high speed PDP8 emulator.
Rumour has it that some hacker also did this on a VAX-11/780, which
would definitely out-run the 11/60 version.
-----
I wonder if the custom microcode is still around?
Ben.
25 Oct
25 Oct
12:16 p.m.
On Oct 24, 2025, at 6:14 PM, ben via cctalk
<cctalk(a)classiccmp.org> wrote:
On 2025-10-24 2:23 p.m., Cameron Kaiser via cctalk wrote:
That did seem
to speed things up too,as well.
-----
From the PDP-11 FAQ.
Fastest PDP-8
Trivia item: did you note anywhere that the 11/60 was used to implement the world's
fastest PDP-8? The 8 support group for years used an 11/60 RSTS system down the hall,
running custom microcode addons to implement a high speed PDP8 emulator.
I don't know about PDP-8 support. The 11/60 with PDP-8 microcode I know of was used
by the WPS-8 development group when it was in Merrimack, NH, next door to the Typeset-11
group where I started in 1978.
OS level
caching of disk devices is a gennable option in M+ with split I/D.
Oh, *disk*
caching! Sorry, I read that as *processor* cache. That makes sense. Rumour has it that some hacker also did this on a
VAX-11/780, which would definitely out-run the 11/60 version.
I don't know about that rumor, and depending on the micromachine architecture it might
not outrun the 11/60 version.
I wonder if the custom microcode is still around?
I asked its author and was told "unfortunately not".
paul
24 Oct
24 Oct
3:11 p.m.
The first SyQuest, the SQ306 3.9-inch cartridge disk drive had an ST506 (MFM) interface -
big issue was unmodified DOS could not deal with a cartridge change but as I recall that
problem was fixed by taking control of INT13 after boot
The next 5¼-inch SyQuest generation was SCSI.
There were other such early cartridge disk drives in various diameters with dumb data bit
serial interfaces such as SMD and most were MFM.
Tom
-----Original Message-----
From: Jim Davis <jim.p.davis(a)gmail.com>
Sent: Thursday, October 23, 2025 1:25 AM
To: General Discussion: On-Topic and Off-Topic Posts <cctalk(a)classiccmp.org>
Subject: [cctalk] Re: MFM Hard Drive & 8" Double Side Drives
I probably have 10 MFM drives, I don't expect any to run. I took one apart, It had
crud on the platter from the air bleed filter.
Smallest I have maybe a couple 20 Mb, Classic seagate ST220?, up to a 100 MB maxtor
XT1105. I have time to test and all the old toolds, I'll give it a try, I need to dig
out a old PC, Goodwill was good to me in the early 2000's I was stupid and passed on a
datapoint 2200, No where to store. Also a old hammond organ, Classic. and cringe.
Probably after Christmas, Might want to consider an alternative.
Just got a new toy (hantek 2d10) scope that is not working right, Op malfunction? . Rigol
was pissing me off.
Fortunately, Got two, one for a gift, So, a reference or another turd.
Was anything MFM or RLL with a removible cart build in the 80's-90's?
I never heard of such a thing, Carts were scsi early 90's Syquest and others?...
On Wed, Oct 22, 2025 at 4:18 PM Mike Katz via cctalk <cctalk(a)classiccmp.org>
wrote:
I just purchased an old Gimix computer (now if only I
can get it from
Orlando to Chicago before my friend goes down there for Christmas).
It has an OMTI 20C-1 MFM hard disk controller with a IMI 5018 19MB
hard disk drive in it.
I am thinking of trying to upgrade the hard drive. The Gimix System
that I worked on had a half high 20MB drive and a Syquest removable
5MB drive.
Does anyone have an old MFM drive laying around (half high or full
height but larger than 18MB) and/or an MFM removable cartridge drive
with cartridges?
I am also going to try to rebuild a Vector Graphic Dual Store Dual 8"
drive enclosure that I picked up at VCFMW. It suffered some dampness
damage and I'm not sure the drives will come up. If you have a dual 8"
drive setup (double sided drives, and enclosure) that you need a good
home for, please let me know.
I'm in the Chicago Area.
Thanks,
Mike
bitwiz(a)12bitsbest.com
23 Oct
23 Oct
2:01 p.m.
On 10/22/25 18:04, Mike Katz via cctalk wrote:
I just purchased an old Gimix computer (now if only I
can get it from
Orlando to Chicago before my friend goes down there for Christmas).
It has an OMTI 20C-1 MFM hard disk controller with a IMI 5018 19MB hard
disk drive in it.
I am thinking of trying to upgrade the hard drive. The Gimix System
that I worked on had a half high 20MB drive and a Syquest removable 5MB
drive.
Does anyone have an old MFM drive laying around (half high or full
height but larger than 18MB) and/or an MFM removable cartridge drive
with cartridges?
Pretty sure Mr Gesswein is on this list but I don't see him post often.
Anyway, he designed a very handy MFM drive emulator:
https://www.pdp8online.com/mfm/mfm.shtml
I won't be buying any more MFM drives, and like Jim said, the ones I
have I wouldn't trust enough to ship. With an inexpensive emulator
available that's one piece of history I won't miss at all.
Doc
2:37 p.m.
On Thu, Oct 23, 2025 at 5:18 PM Doc Shipley via cctalk <
cctalk(a)classiccmp.org> wrote:
On 10/22/25 18:04, Mike Katz via cctalk wrote:
I have two of those MFM emulators for my PDP-11/23+ and PDP-11/23 and they
work great.
-Peter
I just purchased an old Gimix computer (now if
only I can get it from
Orlando to Chicago before my friend goes down there for Christmas).
It has an OMTI 20C-1 MFM hard disk controller with a IMI 5018 19MB hard
disk drive in it.
I am thinking of trying to upgrade the hard drive. The Gimix System
that I worked on had a half high 20MB drive and a Syquest removable 5MB
drive.
Does anyone have an old MFM drive laying around (half high or full
height but larger than 18MB) and/or an MFM removable cartridge drive
with cartridges?
Pretty sure Mr Gesswein is on this list but I don't see him post often.
Anyway, he designed a very handy MFM drive emulator:
https://www.pdp8online.com/mfm/mfm.shtml
I won't be buying any more MFM drives, and like Jim said, the ones I
have I wouldn't trust enough to ship. With an inexpensive emulator
available that's one piece of history I won't miss at all.
Doc
4:46 p.m.
On Oct 23, 2025, at 5:01 PM, Doc Shipley via cctalk
<cctalk(a)classiccmp.org> wrote:
On 10/22/25 18:04, Mike Katz via cctalk wrote:
I thought I sent Dave my results for the Pro. I've used it to read RD51 and RD52 (the
one from Quantum). I've emulated those and RD50 and I think also RD53. Don't
remember if I tried emulating any of the other drive models the Pro supports, such as the
other two RD52 flavors. It isn't hard to do that so long as you know the geometry.
BTW, on the Pro all drives have 16 sector tracks, even if they can and do have more
sectors using other controllers.
paul
I just purchased an old Gimix computer (now if
only I can get it from Orlando to Chicago before my friend goes down there for Christmas).
It has an OMTI 20C-1 MFM hard disk controller with a IMI 5018 19MB hard disk drive in it.
I am thinking of trying to upgrade the hard drive. The Gimix System that I worked on had
a half high 20MB drive and a Syquest removable 5MB drive.
Does anyone have an old MFM drive laying around (half high or full height but larger than
18MB) and/or an MFM removable cartridge drive with cartridges?
Pretty sure Mr Gesswein is on this list but I don't see him post often. Anyway, he
designed a very handy MFM drive emulator:
https://www.pdp8online.com/mfm/mfm.shtml
6
days inactive
9
days old
17 comments
10 participants
participants (10)
-
ben -
Cameron Kaiser -
Christopher Zach -
cz
-
Doc Shipley -
Jim Davis -
Mike Katz -
Paul Koning -
Peter Ekstrom -
Tom Gardner