2 Nov
2013
2 Nov
'13
2:13 p.m.
On Sat, Nov 02, 2013 at 08:17:47PM -0000, Robert Jarratt wrote:
I had a look and it seems close to what I would need,
but possibly not
quite. It says it will do 400mips, which for a sampling frequency of 40MhZ
would give me 10 instructions per sample (crude assumption I know), but it
is not clear to me if each core does 400mips, or if that is 400mips
aggregated across 8 cores (which seems more likely), which would give my
just 1 instructions per sample. Do you know which it is?
It's the second one, so I was picturing a little hardware help. If something
outside helps measure pulse lengths, shoveling those into the chip isn't so
bad, and then the receiver thread can hand off to a mark-detection thread or
whatever and keep the main code path short.
XMOS went insane about a year ago and replaced all the plain English on
their website with severe market-talk so you can't tell what anything really
is. The actual point is that on a 100 MHz clock, or maybe 125 MHz or
possibly 175 MHz with newer chips, the processor executes one instruction
from each of the next four threads in line, and then
moves them to the back
of the line (which is still the front of the line if
you're only using <= 4
threads).
There is a nice little affordable starter kit board,
the XK-1A, which is
even available in the UK,
You mean it's even available outside the UK. It's *from* the UK!
but it doesn't have enough on board memory to
store a cylinder (which I now realise would need to be up to 500Kbytes per
cylinder if I am storing samples at 40Mhz, it could store a track though),
The 64 KB limit can be a problem. OK sounds like not a good fit for this.
Sorry! I've been using them for reading floppies with all software and it's
worked great, so I was figuring a little hardware would bridge the gap to the
HD (5x faster than 2.88 MB FDs isn't *such* a huge jump with HW help, and if
you're the drive the timing can be a bit more approximate than a controller
which needs to write media that will still interchange).
My thought was that if I can get this to work it
wouldn't then be a big step
to modify it to work in the opposite direction and use it to image old disks
before they finally die.
Absolutely. A device that helps you start using itself will get used! Nice.
John Wilson
D Bit