USB Universal Floppy Disk controller

[Philip Pemberton]

In message <1110561380.6178.63.camel at weka.localdomain>
          Jules Richardson <julesrichardsonuk at yahoo.co.uk> wrote:

> Well if worst-case is 1mbps data rate at 300rpm and 8x oversample, isn't
> that (8 * 10240 * 1024) / 5 = 1677722 bits of memory maximum needed?
> 
> (div by 5 because 300rpm gives you a whole track in 1/5 of a second)

And therein lies the error in my calculations. I came up with 1MByte per
track...

> Presumably there's no need to have any kind of microprocessor control;
> it can all be done with a free-running clock to read from the drive or
> write to it, and a few control lines to for read/write, start, stop etc.

Why not stuff it all in a CPLD? Maybe create a logic-only version too...

> Can static RAM can't cope with these kinds of speeds? Presumably cache
> chips pulled from old PC motherboards would cope happily, even if old
> 80's parts wouldn't.

70nS SRAM should work fine, and most SRAM is pretty cheap too. I've got a
512kbit here that cost about £4 and is rated to 70nS IIRC.

> > Aaghh! That reminds me - it's a good year since I backed up the HDD on my
> > machine... [fx: hard drive starts going kaclunk-kaclunk-kaboooom]
> 
> Oh boy. I rsync data from my desktop to an external hard disk
> periodically (usually once or twice a week). Hadn't done it for a few
> weeks, kicked off a run the other day, and the wholse SCSI subsystem
> fell over. 

I really should look into buying an external USB hard drive casing and a
server-rated IDE/ATA hard drive (probably a Maxtor MaXLine II or a Seagate
Barracuda)

> Panic for a moment, thinking my desktop drive had died. Turns out I'd
> set the SCSI data rate to the external disk higher than normal when I
> was playing around with something else, and forgotten to set it back
> again - so it was just a SCSI bus transfer problem, not a hardware
> issue. Phew.

You're using SCSI in a desktop system? Heh. I should probably see about
trying that sometime.

Later.
-- 
Phil.                              | Acorn Risc PC600 Mk3, SA202, 64MB, 6GB,
philpem at philpem.me.uk              | ViewFinder, 10BaseT Ethernet, 2-slice,
http://www.philpem.me.uk/          | 48xCD, ARCINv6c IDE, SCSI
... DOS means never having to live hand-to-mouse