11 Mar
2005
11 Mar
'05
2:10 p.m.
In message <1110561380.6178.63.camel at weka.localdomain>
Jules Richardson <julesrichardsonuk at yahoo.co.uk> wrote:
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)
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. 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