Its cool, but would be far better if the mech was available with it.... never heard of 4 1/2 media before. I have tons of the Amdek 3 1/4 disks for its amdisk drives, those a neat, like the hard plastic shells on them. I used to have, I'm gonna say Toshiba??? 2" or 2 1/2" disks for a while, but someone had a working portable, so we made a trade, but those were really interesting. Chris Tofu wrote:

On Tue, 24 Jul 2012, Curt @ Atari Museum wrote: THOSE are called "THREE INCH". In addition to being used in Amstrad computers, Amdek peddled external drive units for Apple][! and for Coco. They are nice. Many of us prefer them over the 3.5" The ones that are called "3 1/4" were floppy cased disk from Dysan. Despite betting the company on it, and spending a lot, Dysan failed to get them to become the standard - Seequa Chameleon 325 was the only machine to make it to market with those drives. I wonder how many of them they actually sold?

True, I can see one from here. The floppy controller could handle 5 drives (as most contorllers could befor the IBM 5150). You could connect 2 extrnal drives. Adn AFAIK you could have 3.5" or 5.25" extrenal drives if you wanted to. The einstein was a curious machine. It was clearly pitched as a competitor to the BBC nicro [1]. In some respects it was superior -- it had 64K user RAM, none of which was taken for video, it always had a disk drive, in others it was inferior (the video system, based round the 50Hz versio nof the 9918 (is that a 9927 or something?) could only do 40 column text. Both the Beeb and the Einstein had a serial port [2], parallel printer port, and user port as standard. Of course the Beeb was a 6502-based machine, the Einstein was Z80A-based, I refust to start that flamewar ;-) [1] As you may know, there was an interface on the BBC micro called the 'Tube', noramlly used to conenct to second processors. The official reason for the name was that it was a thing oyou oculd push datat down, but it was clear that the obvious (to a Brit) pun was intentional [The Tube is a common name for the London Underground railway (==subway), which is, of course an alternative form of public transprot to a bus (omnibus). The Einstein expansion bus is called the 'Pipe', presumably related to a 'tube'. [2] Both the Beeb and the Einstein have a quincuncial 5 pin DIN connector for the serial port. This connector fits either way up. Plugging it in the wrong way up on a BBC micro does nothing useful,. doing that on an Einstein swaps TxD and Rxd, and alos RTS with CTS -- effecively giving an null modem swap. One very odd feature o the Einstein serial port is that the DSR and DTR signals are avaialble on labelled solder pads o nthe PCB. I can't believe anyone ever used them. -tony

On 25 Jul 2012 at 13:59, Fred Cisin wrote: Depending on the vintage of the TRS-80, that's not as silly as it sounds at first. Didn't most of the early 8" drives (e.g. SA-800) have a configurable option for either radial or binary select? --Chuck

On 25 Jul 2012 at 19:30, Geoff Reed wrote: .> some of the aftermarket disk controllers allowed up to 4 devices If you had some 8" drives that allowed binary select, some controllers, depending on how drive select was implmented (demux vs. simple latch) could probably select up to 16 drives. --Chuck

On 26 Jul 2012 at 10:06, Fred Cisin wrote: Good observation--yes, I suppose so. --Chuck

Yes, unfrotunately it was a typo. The Einstein controller (along with most others of the time) could handle 4 (four) floppy drives. It should be psosible, IIRC on the TRS-80, each sleect line could be independantly controlled in software, so you could use a binary encoding scheme. I am not sure that was an improvement :-) -tony

On Tue, 24 Jul 2012, Chris Tofu wrote: Except that as soon as it sold, he "relisted" to sell another of them. Once you get it, then you can start the process of trying to find one of the DRIVES! -- Grumpy Ol' Fred cisin at xenosoft.com