UCSLCT@UWPLATT.EDU (LANCE TAGLIAPIETRA) (05/04/90)
Hello, I just finished reading an informative article in The Computer Journal Issue 44: Mysteries of PC Floppy Disks Revealed by Richard Rodman. I had always wondered how 1.2M and 1.44 Meg storage was achieved on 5.25 and 3.5 inch hardware. I am glad to see an article covering this territory. The article did bring a couple questions to mind: (1) What is the difference between 720K and 1.44M 3.5 inch drives. (2) What is the pinout for 3.5in drives. (a pinout for 5.25in is given) Can anyone shed light on this? Lance Tagliapietra (ucslct@uwplatt.edu) or (ucslct@uwplatt.bitnet)
mollers.pad@nixpbe.uucp (Moellers) (05/07/90)
UCSLCT@UWPLATT.EDU (LANCE TAGLIAPIETRA) writes: >Hello, > >I just finished reading an informative article in The Computer Journal >Issue 44: Mysteries of PC Floppy Disks Revealed by Richard Rodman. > >I had always wondered how 1.2M and 1.44 Meg storage was achieved on >5.25 and 3.5 inch hardware. I am glad to see an article covering this >territory. > >The article did bring a couple questions to mind: > >(1) What is the difference between 720K and 1.44M 3.5 inch drives. The 1.44M drive has twice the bit-density of the 720K disks. I.e. both have 80 tracks/side but the 1.44M drive has twice the number of bits (and therefore bytes and sectors) per track. >(2) What is the pinout for 3.5in drives. (a pinout for 5.25in is given) As far as I know, they are the same (I use both drives on the same flat-cable, the 5.25" connected with the usual edge-connector, the 3.5" connected with a berg-type connector. HOWEVER: there are drives that can use some of the pins for more than one purpose (e.g. drive ready vs. disk change, something else vs. high density etc). >Can anyone shed light on this? Hope this did! >Lance Tagliapietra (ucslct@uwplatt.edu) or (ucslct@uwplatt.bitnet) | Josef Moellers | c/o Nixdorf Computer AG | | USA: mollers.pad@nixbur.uucp | Abt. PXD-S21 | | !USA: mollers.pad@nixbur.uucp | Pontanusstr | | Phone: (+49) 5251 146245 | D-4790 Paderborn |
"Rex_E._Robards.DlosLV"@XEROX.COM (05/07/90)
In message-id 9DD0D3D47EDF602A04@uwplatt.edu, Lance Tagliapietra asks, > (1) What is the difference between 720K and 1.44M 3.5 inch drives. 1.44 MB drives have 18 sectors per track. 720 KB drives have 9 sectors per track. >(2) What is the pinout for 3.5in drives. (a pinout for 5.25in is given) The pinout for 3.5" drives is the same (3.5" drives are indistinguishable from 5.25" drives from a hardware perspective). Rex (rroba.dloslv@xerox.com)
mcmiller@uokmax.uucp (Michael C Miller) (05/09/90)
In article <1682@nixpbe.UUCP> mollers.pad@nixpbe.uucp (Moellers) writes: > >As far as I know, they are the same (I use both drives on the same >flat-cable, the 5.25" connected with the usual edge-connector, the 3.5" >connected with a berg-type connector. Hi there ! If you are connecting to the 5.25 ribbon cable you must have the 3.5 drive mounting assembly ( like the ones used for PCs ). The actual pin outs from the drive control board are a little different. I have some docs on a SSSD Sony 3.5 and they list the pins differently. If you need the info, let me Know and I'll be happy to send it along to you. ....michael -- Better Dead than Simply Red!!!!! < sans => mcmiller@uokmax.UUCP or mcmiller@uokmax.ecn.uoknor.edu > < '..this one goes up to eleven. Its ONE louder.' >
tilmann@cosmo.UUCP (Tilmann Reh) (05/09/90)
Hello.
> Can anyone shed light on this?
I hope so. Generally, the 3.5" and 5.25" drives are IDENTICAL, concerning
their electrical and logical details. There is NO WAY to distinguish a 3.5"
drive from a 5.25" drive by software. As far as I know, the pinout is also
identical (however, the 'AT compatible' drives have some special pinout, for
both 3.5" and 5.25"). But, most 3.5" drives use pin connectors instead of
the card-edge 5.25" types.
The different capacities are the result of different data rates. The 720k
formats (both 3.5" and 5.25") are obtained using a data rate of 250 kbit/s
in MFM mode, so one track will contain 9 512-byte sectors per side.
The 1.44M format (only 3.5", as 5.25" drives for that data rate aren't
manufactured) uses a data rate of 500 kbit/s (like 8" drives) with MFM, so
18 such sectors fit onto one track.
The 1.2M format (5.25") is strictly an 8" format: the 5.25" HD drives are
rotating with 360 rpm, so that they behave exactly like an 8" DS DD drive.
Again, there is NO WAY to distinguish by software...
When using different capacities (and/or) different drives, always be sure
to use disks and drives only within their specifications! The HD disks
(5.25" 1.2M and 3.5" 1.44M) use stronger magnetic fields than the normal
MFM disks, so you can't crossover HD disks with MFM formats and vice versa.
However, if you try to format a normal disks for HD, it may be permanently
damaged (with resident magnetism caused by the strong fields).
Besides, always be aware that the capacities 720k and 1.44M (as well as 360k)
do NOT use all legal resources of disk and drive. It's just that IBM (who else)
wasted about 10 / 18 percent of the possible capacity FOR NO REASON!
Formatting MFM disks with 10 x 512 byte or, even better, 5 x 1024 byte, would
give 400k (40 track) or 800k (80 track) net capacity, and all that within
all specifications of the IBM 3740 disk format.
Formatting HD disks with 20 x 512 byte would give 1.6M, with 11 x 1024 byte
1.76M (that is 22% more than IBM!), also legal.
Again, one example how performance is WASTED by a company of which still
some people think they were able to design computers...
Tilmannwilker@hopf.math.purdue.edu (Clarence Wilkerson) (05/26/90)
Are there any cheap "bare board" kits for 64180's or Z280's out there, say less than $50 for a PCB? CT' mag in Germany used to sell this kind of stuff, but I have not heard of suppliers in the USA for the hard core hardware hackers. The BYTE Ciarcia board comes to mind, but is more money than I want to spend on whim.
tilmann@cosmo.UUCP (Tilmann Reh) (05/27/90)
dg@pallio.UUCP (David Goodenough) writes: > So does the 1793. At least the 1793 in my Televideo 803 seems to talk quite > happily to all four drives attached. Of course it does. The hardware developers had to do by extra hardware what the chip didn't support. As a result, it is impossible to step four drives simultanously, while always watching all four 'READY' lines (just an example). > I've worked with both the 1793, and the 765, and the > software overhead for the 765 is way higher than that for the 1793. Unless you try to achieve the overall comfort and performance of the 765, I agree... (Just think of the 'READY changed' interrupt.) > Fooling with the bits _DOES_ have it's advantages: And it's disadvantages. All the troubles with different disk formats are caused by people who wanted to create 'their own format', incompatible to everything else (or to get slight features, thereby nevertheless becoming incompatible). And now you try to argue for a format with different sector sizes on one track. I strongly recommend that NOONE should ever use such a format. This method, together with irregular sector (or track!) numbering should be forbidden anyway. Not for the 765, but for some basic rules. High disk capacities, OK. But only the legal way, s'il vous plait. > I'll agree with that when I see it put 440K on a DS DD floppy. Independent of the previous: please show me a member of the x79x family with the whole floppy interface (as mentioned earlier) on a SINGLE CHIP ! Just fits in the gap between CPU and FDD. No glue logic, no clocks, no PLL, even no drivers! (You see, I'm hardware designer) Tilmann Reh
SLSW2@cc.usu.edu (Roger Ivie) (05/30/90)
In article <5715@balu.UUCP>, tilmann@cosmo.UUCP (Tilmann Reh) writes: > > Independent of the previous: please show me a member of the x79x family > with the whole floppy interface (as mentioned earlier) on a SINGLE CHIP ! > Just fits in the gap between CPU and FDD. No glue logic, no clocks, no PLL, > even no drivers! Of course, the only reason you can get 765s like that is because IBM used the 765. Noone wants to build new x79x chips anymore, since they would be incompatible with the IBM market. -- =============================================================================== Roger Ivie 35 S 300 W Logan, Ut. 84321 (801) 752-8633 ===============================================================================