I added a new page to my website dealing with disks and disk drives. Some of it is CP/M specific but it may be of interest to many on this list. It is a work in progress: http://www.s100-manuals.com/Disk-drives.htm If anyone sees any errors in it let me know off-list. Randy www.s100-manuals.com

I never heard of a 3.25" floppy, but there was a 3" version. It was used by Amstrad (possibly others too ? ) Nico ----- Original Message ----- From: "Gene Ehrich" <gehrich at tampabay.rr.com> To: <cctalk at classiccmp.org> Sent: Tuesday, March 08, 2005 10:04 AM Subject: three and a quarter inch floppy?

The Oric is another one (yes, there was an Oric floppy drive). I've also seen 3" drives (the Hitachi ones have standard SA400-like interfaces) used on BBC micros, Tandy CoCos, etc. -tony

David wrote: IIRC, Dysan was acquired by Verbatim.

On Tue, 8 Mar 2005, Vintage Computer Festival wrote: Yes, I gave you one (possibly an alignment disk!) at VCF a few years ago. In addition, in the files and ephemera from my office, there were some Dysan spec sheets. -- Grumpy Ol' Fred cisin at xenosoft.com

31/4 drives were used on the old Amstrad word processing machines (forget the number - do any of the other UK members know? Jim. ----- Original Message ----- From: "Gene Ehrich" <gehrich at tampabay.rr.com> To: <cctalk at classiccmp.org> Sent: Tuesday, March 08, 2005 9:04 AM Subject: three and a quarter inch floppy?

On Tue, 2005-03-08 at 19:41 +0000, Adrian Graham wrote: Yep, I remember them being 3" too. I hate to think how many drive belts I've replaced on them when I worked for a repair place many years ago. J.

PCW8256? The Amstrad drives were certainly belt-driven (and replacing the belt was a common job). The Hitachi drives I've used (single and double head) had direct-drive spindle motors, though. -tony

On Tue, 8 Mar 2005, Gene Ehrich wrote: Yes, I've heard of them. I have some, and some of those drives in my collection. At one point, it became inevitable that the next stage in floppies would be "shirt pocket disks. There were four contenders: Sony 3.5", 3" (as used in Amstrad), 3.25" from Dysan, and 3.9" from IBM. The IBM 3.9" was the first to give up - there do not appear to have been ANY machines using it. Now there were three. The pundits in the industry argued long and hard about the relative advantages of the three contenders. That prompted George Morrow to suggest that the solution was to simply cut a deal with the clothing industry to make shirt pockets a lot larger (5.25", or even 8"). Both the 3.5" and 3" had hard plastic shells that made them able to withstand much of the abuse that had been the bane of the 8" and 5.25" disks. The 3" was available in a single sided, a "flippy", and a double sided form. The 3.5" chose to closely match the formats of 5.25" "720K" "quad density" disks. The first 3.5" disks had no shutter (Shugart, etc.), the next series had a spring loaded shutter that had to be manually opened, and pinching the corner released the shutter to close it again. Finally, a fully automatic spring loaded shutter was available. Interestingly, many of the later disks still had a little arrow embossed on them, that once pointed to the loacation to squeeze to release the shutter. But Dysan wanted to go with a design that would require minimum retooling of their factories - a 3.25" disk that was the same as a 5.25", except for a metal center hub. Since many of the media and industry pundits assumed that the race would go to the one with software availability, Dysan bet the company on a software publishing venture. Before there were ANY computers using them, Dysan had provided drives and diskettes to major software vendors, and soon, a significant portion of the major commercial software titles could be purchased directly from Dysan! A few computer manufacturers strated designing computers with 3.25" disks. The Seequa Chameleon 325 appears to be the only one that actually made it to market, although with Seequa's reputation for vaporware, it is not clear how many, if any, were ever actually sold. Amstrad (a large British computer company) chose to go with the 3". In addition, Amdek produced external drive units that were marketed for Apple ][ and RS Color Computer. Gavilan briefly used 3" disks, and then switched to 3.5". Meanwhile, HP, and then Apple, and then IBM went with 3.5", which created the new defacto standard. Dysan gave up on their 3.25" disk system. Now there were two. The industry dominance of IBM, Apple, and HP created a defacto standard, and the 3" eventually died. Now there is one. The later versions of the 3.5" use3d a higher coercivity disk, and held 1.4M, instead of the previous 720K. There were some other variations of the 3.5" physical case, including a 2.8M Berrium-Ferrite disk, and 20M Flopticals. -- Fred Cisin cisin at xenosoft.com XenoSoft http://www.xenosoft.com

On Tue, 8 Mar 2005, Jim Beacon wrote: I have a parallel port MicroSolutions 2.8M drive. Sorry, but I intend to keep it. In addition, some models of Next computers had them (called "4M" for their UNformatted capacity). BTW, in order to call it "2.88M", you would need to use3 the IBM drive de3finition of "megabyte" of 1024000. If you define a Megabyte ("Mebibyte") as 1048576, then "1.44M" has 1.40625 M, and "2.88M" has 2.8125 M. -- Grumpy Ol' Fred cisin at xenosoft.com

In which case, it would be 2.95M 2949120 2 sides * 80 tracks per side * 36 sectors per track * 512 bytes per sector Likewise, a "1.44M" diskette only has 1.44M if you use the IBM "megabyte" of 1024000. If you use an HONEST Megabyte, of 1048576, then it has 1.40625 M. If you use your 1000000 Bytes per Megabyte, then it would 1.47M 1474560 2 sides * 80 tracks per side * 18 sectors per track * 512 bytes per sector Or do you also want a Kilobyte to be 1000 bytes? Byte is 8 bits. Word often varies, though That would depend on YOUR terminology, which could make it be anywhere -- Grumpy Ol' Fred cisin at xenosoft.com

At 02:18 AM 3/13/05 +0000, you wrote: wrote: not Where was that? we were always taught that 8 I've heard that too but it was a LOOONG time ago. I can't even remembe where it or when it was. because the size of a byte varies between WORD sizes varies but a byte is now considered to be 8 bits. Joe http://en.wikipedia.org/wiki/Byte would seem to agree.

In the TCP/IP world, that would most likely come from the terminology of the PDP-10 world (think back to the days of IMPs, etc.) On the -10, one stores 6 6-bit characters in a machine word, and one speaks of bytes that are 6 bits. AFAIK, 'octet' was invented in networking circles to prevent any ambiguity about which size byte one was discussing. Outside of PDP-10 and Cyber circles, "byte" has pretty much meant 8-bits, though. If one only worked on microcomputers (i.e., post 1974), the tug-of-war was over, and byte "always meant 8 bits". -ethan

On Sun, 13 Mar 2005 20:36:58 +0100, Eric Smith <eric at brouhaha.com> wrote: ... A byte is the smallest INDIVIDUALLY addressable unit of data on a system. It was usual to speak of a character when a part of a whole word was extracted. I do not remember any details of the Univac 1107 (I only programmed in FORTRAN and Simula on it), but I think the normal character was six bits. I am fairly certain that was not a byte, it was extracted from an 18-bit halfword or a 36-bit word. A byte is something you can load and store to an individual address, and the hardware takes care of the rest. A character needs some software or firmware mapping in order to read or write just one of them. -- Bj?rn

Bj?rn wrote: I agree with this, but was it universal? For example, programming games for the Intellivision console involved 10-bit memory addresses referred to as "decels" (pronounced DEK-el). You hear decel this, decel that all the time in that niche. -- Jim Leonard (trixter at oldskool.org) http://www.oldskool.org/ Want to help an ambitious games project? http://www.mobygames.com/ Or check out some trippy MindCandy at http://www.mindcandydvd.com/

Depends on whom you ask. In mainstream computing today, yes, a byte is 8 bits. But here, in classiccmp-land, we use - and discuss - a lot more equipment dating from the days when "byte" was much more variable. Much more so than is done in mainstream computing. So here, it's not unreasonable to use "octet" to mean an 8-bit datum and "byte" to mean something less well defined in general, depending on the architecture(s) under discussion. Now, in the original context - which was discussing how "1.44M" and "2.88M" floppies are schizoid about their definition of "M" (it's a product of a 1024 K and a 1000 K), is it reasonable to use byte=8bits? Personally, I'd say it is, since such floppies are 3.5" and thus recent enough that I doubt you'd find one on anything but an 8-bit-byte machine. (Of course, I'm sure this crowd could arrange to have one on a PDP-8 or some such, but the 1.44-megabyte and 2.88-megabyte names make no sense except for byte=8bits.) /~\ The ASCII der Mouse \ / Ribbon Campaign X Against HTML mouse at rodents.montreal.qc.ca / \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B

Jim Beacon wrote: I have a couple of the IBM 2.88MB drives here & there, but I believe they're all in RS/6000 systems, and at least one in an Alpha. I disremember whether any of the PS/2s I have have one. I've never seen a "3MB" floppy disk though. Doc

How does somebody new join this list. Who do they write to, etc ?

At 03:54 AM 3/8/2005, der Mouse wrote: Be polite, be nice! Say hello, *then* kick him out because he's using a Dell on a high-speed link. - John