Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

On Jan 26, 2016, at 10:07 PM, Fred Cisin wrote: >>> 82901A and the HP 9121D now work great. Quite low capacity (270k?) due to >>> the weird LIF formatting, formats 35 tracks but uses only 33, out of the >>> 40. I wonder why. >> Partially because the original 5.25" drives

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

On 01/27/2016 02:07 PM, Eric Smith wrote: The double-density RX02 data fields are in a modifed MFM, which is what M2FM or MMFM stands for. It doesn't use the same encoding rules as are most commonly used for M2FM, though. ...and that was exactly my objection. This becomes a case of the

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

On Wed, Jan 27, 2016 at 9:49 AM, Chuck Guzis wrote: > That's exactly what I was asking. But you implied that the RX02 was MMFM, > which, in my experience is not the case. The double-density RX02 data fields are in a modifed MFM, which is what M2FM or MMFM stands for. It

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

On 01/26/2016 09:07 PM, Eric Smith wrote: On Tue, Jan 26, 2016 at 7:04 PM, Chuck Guzis wrote: You've lost me there. Both HP and Intel were true MMFM; There's more to it than the basic channel code. IBM 3740 and Ohio Scientific 8-inch both use "true FM" for the channel

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

On Tue, 26 Jan 2016, Chuck Guzis wrote: So did Intel on the MDS. I don't recall if there was any significant difference between Intel and HP MMFM encoding, however. The initial CRC value ($ vs. $) and the header (six vs. four bytes) are different, but the encoding was quite

RE: Substituting DSHD for DSDD disks (or DS2D if you prefer)

On Tue, 26 Jan 2016, CuriousMarc wrote: You make me feel lucky. I have all 3 (almost, I have the low density HP 9121 rather than an HD 9122 so I can use it on my HP 85)... Haven't restored or even powered up the recently acquired HP 9895 yet, but the HP 82901A and the HP 9121D now work great.

RE: Substituting DSHD for DSDD disks (or DS2D if you prefer)

82901A and the HP 9121D now work great. Quite low capacity (270k?) due to the weird LIF formatting, formats 35 tracks but uses only 33, out of the 40. I wonder why. Partially because the original 5.25" drives (Shugart SA400) were 35 track (#0 - #34), not 40. I don't even remember, . . . Does

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

On Tue, Oct 27, 2015 at 7:47 AM, Paul Berger wrote: > I would really > like to get a HP 9895 8" drive but they seem to be few and far between. Same here. And I'd like to get an 82901M 5.25" drive, and a 9122C HD 3.5". I was surprised to learn that the 9895, while it supports

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

On 2016-01-26 6:48 PM, Eric Smith wrote: On Tue, Oct 27, 2015 at 7:47 AM, Paul Berger wrote: I would really like to get a HP 9895 8" drive but they seem to be few and far between. Same here. And I'd like to get an 82901M 5.25" drive, and a 9122C HD 3.5". I was surprised to

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

On 01/26/2016 02:48 PM, Eric Smith wrote: I was surprised to learn that the 9895, while it supports standard IBM 3740 single-density format, uses an HP-proprietary M2FM double-density format. So did Intel on the MDS. I don't recall if there was any significant difference between Intel and

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

On 01/26/2016 05:27 PM, Eric Smith wrote: Entirely different. As was DEC RX02. You've lost me there. Both HP and Intel were true MMFM; the RX02 was single-density headers and a somewhat modified MFM (probably to avoid false FM address mark triggering on MFM sequences. --Chuck

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

>Paul Berger wrote: >On 2015-10-26 11:38 AM, Jules Richardson wrote: >On 10/24/2015 09:14 PM, Fred Cisin wrote: Are we really running short of "720K" floppies? I went around all the local places that I could think of a couple of years ago and bought up whatever stock of floppies that I

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

On 2015-10-27 10:53 AM, Jerome H. Fine wrote: >Paul Berger wrote: >On 2015-10-26 11:38 AM, Jules Richardson wrote: >On 10/24/2015 09:14 PM, Fred Cisin wrote: Are we really running short of "720K" floppies? I went around all the local places that I could think of a couple of years ago

RE: Substituting DSHD for DSDD disks (or DS2D if you prefer)

[HD 3.5" disks and the density-select hole] > Of course, on a DD-only drive, the drive is blind to the extra hole. Not always! The original Sony full-height drives (the 600rm ones) have a disk-inserted sensor positioned exactly where that hole is. So if you insert an HD disk the drive doesn't

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

On 10/25/2015 11:12 PM, tony duell wrote: Not always! The original Sony full-height drives (the 600rm ones) have a disk-inserted sensor positioned exactly where that hole is. So if you insert an HD disk the drive doesn't detect it. It is rumoured this was deliberate (positioning of the HD hole)

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

and the first hp-150 drive set, the hp-9121, was single sided double density SS/DD discs (270Kb). sure was glad when the 9122 came out! Always looking for more HP-150 stuff for our display... any one have a monarch butterfly advertising poster? Ed# _www.smecc.org_

RE: Substituting DSHD for DSDD disks (or DS2D if you prefer)

> > Yes, the Sony OA-D32 drives. Single-sided 600 RPM. One *could* argue, > that, given the data rate, it's already "high density" (of a sort). I I would say it's normal double density (the spacing of the flux transitions on the disk is the same as on a PC 720K disk) but a high data rate due

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

On 2015-10-26 11:38 AM, Jules Richardson wrote: On 10/24/2015 09:14 PM, Fred Cisin wrote: Are we really running short of "720K" floppies? I went around all the local places that I could think of a couple of years ago and bought up whatever stock of floppies that I could find (and picking

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

On 10/24/2015 09:14 PM, Fred Cisin wrote: Are we really running short of "720K" floppies? I went around all the local places that I could think of a couple of years ago and bought up whatever stock of floppies that I could find (and picking sure were slim). Quite a few boxes of 3.5" HD, a

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

On Mon, 26 Oct 2015, Jules Richardson wrote: On 10/24/2015 09:14 PM, Fred Cisin wrote: Are we really running short of "720K" floppies? I've never had any luck finding used disks anywhere locally; people are a bit too concerned about data theft these days, and all of that seems to go

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

On 10/26/2015 01:04 AM, couryho...@aol.com wrote: and the first hp-150 drive set, the hp-9121, was single sided double density SS/DD discs (270Kb). sure was glad when the 9122 came out! I supsect that the Sony SMC-70 may have been among the first systems to come out with the things.

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

Chuck good to know we probably need some - I do not think we have any good clean ones new here... will check Ed# In a message dated 10/26/2015 9:50:44 A.M. US Mountain Standard Time, ccl...@sydex.com writes: On 10/26/2015 01:04 AM, couryho...@aol.com wrote: > and the

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

On Sat, 24 Oct 2015, Fred Cisin wrote: Are we really running short of "720K" floppies? I thought that AOHell had sent out enough snail spam with disks to supply us forever! Indeed, but the quality of those diskettes was dreadful. --

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

This list seems to me to be populated with "build your own" types, so make your own degausser. Decades ago I repaired the tape eraser at the TV station I worked at. Once I saw how it was built I built my own. Take a transformer (something about 100 watt or more) pull the laminations out (the

RE: Substituting DSHD for DSDD disks (or DS2D if you prefer)

> -Original Message- > From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Steven > Hirsch > Sent: 25 October 2015 13:08 > To: General Discussion: On-Topic and Off-Topic Posts > > Subject: Re: Substituting DSHD for DSDD disks (or DS2D if you prefer) >

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

On Sun, Oct 25, 2015 at 3:05 PM, Eric Christopherson < echristopher...@gmail.com> wrote: > On Sun, Oct 25, 2015, Joseph Lang wrote: > > This list seems to me to be populated with "build your own" types, so > make your own degausser. > > Decades ago I repaired the tape eraser at the TV station I

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

On 10/25/2015 09:19 PM, Eric Christopherson wrote: Also, do I always need to cover one hole on a 3.5" HD disk when using it in an HD-capable drive? Or does the disk or the OS notice it's been formatted as DD and then treat it accordingly? In *most* applications, the extra hole in the HD

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

On Sun, 25 Oct 2015, Eric Christopherson wrote: Actually, in many areas of the US, they had local dialup numbers that connected to their service through Tymnet and/or Telenet, so long distance didn't apply. Maybe in rural areas those access points were still long distance, though. But AOL itself

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

On 10/25/2015 01:07 PM, Eric Christopherson wrote: Actually, in many areas of the US, they had local dialup numbers that connected to their service through Tymnet and/or Telenet, so long distance didn't apply. Maybe in rural areas those access points were still long distance, though. But AOL

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

On 10/25/2015 01:36 PM, Fred Cisin wrote: 3 years ago, when I stayed at my mother's house taking care of her, it took me a month to find out that she did not have unlimited local calling! Adding DSL on the phone account reduced the phone bill a lot. That house is now mine. AT DSL here sucks.

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

On 10/25/2015 7:07 AM, Steven Hirsch wrote: On Sat, 24 Oct 2015, Fred Cisin wrote: Are we really running short of "720K" floppies? I thought that AOHell had sent out enough snail spam with disks to supply us forever! Indeed, but the quality of those diskettes was dreadful. More the Service

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

On Sun, Oct 25, 2015, Joseph Lang wrote: > This list seems to me to be populated with "build your own" types, so make > your own degausser. > Decades ago I repaired the tape eraser at the TV station I worked at. Once I > saw how it was built I built my own. Take a transformer (something about

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

Are we really running short of "720K" floppies? I thought that AOHell had sent out enough snail spam with disks to supply us forever! Indeed, but the quality of those diskettes was dreadful. On Sun, 25 Oct 2015, ben wrote: More the Service provided from the disk.? Blaming the medium for the

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

On 10/25/2015 1:03 PM, Fred Cisin wrote: Blaming the medium for the content? Or, . . . if you were putting something like that onto disks, would you spring the money for high quality ones? I suspect the reason they failed was not service but a) PC's had games b) Ma Bell wanted a arm and a

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

On Sun, Oct 25, 2015, ben wrote: > On 10/25/2015 1:03 PM, Fred Cisin wrote: > > > > >Blaming the medium for the content? > >Or, . . . > >if you were putting something like that onto disks, > >would you spring the money for high quality ones? > > > I suspect the reason they failed was not service

Substituting DSHD for DSDD disks (or DS2D if you prefer)

I know Chuck Guzis has written about this, but I don't see that he's done so publicly in the last few years, so I thought I'd ask here about his and others' views on the perennial question of whether (some) 3.5" DSHD disks can be reliably used in DSDD-only drives. The oft-repeated claim is that

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

On 10/24/2015 06:59 PM, Eric Christopherson wrote: I know Chuck Guzis has written about this, but I don't see that he's done so publicly in the last few years, so I thought I'd ask here about his and others' views on the perennial question of whether (some) 3.5" DSHD disks can be reliably used

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

On Sat, Oct 24, 2015 at 9:14 PM, Fred Cisin wrote: > On Sat, 24 Oct 2015, Eric Christopherson wrote: > >> I know Chuck Guzis has written about this, but I don't see that he's done >> so publicly in the last few years, so I thought I'd ask here about his and >> others' views

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

On Sat, 24 Oct 2015, Eric Christopherson wrote: I know Chuck Guzis has written about this, but I don't see that he's done so publicly in the last few years, so I thought I'd ask here about his and others' views on the perennial question of whether (some) 3.5" DSHD disks can be reliably used in

Re: Substituting DSHD for DSDD disks (or DS2D if you prefer)

On 10/24/2015 09:06 PM, Eric Christopherson wrote: Fascinating -- I didn't know there were AC and DC magnetic fields. How strong is "very strong", and would the library device I mentioned count toward "an AC erase"? Should I assume that just doing an AC erase would be insufficient? The AC