How big is a nanosecond?

Ralph DiMola rdimola at evergreeninfo.net
Sun May 5 13:37:58 EDT 2019


This not a limit without real world consequences...

I was hamstrung with the 1 foot per nanosecond limitation back in 1979. We
had a CGI rack with a 6 foot backplane clocked at 25 MHz Of course 1 foot/ns
is a theoretical limit. Although we had 40 ns we ran into not only the time
it took to get from the bottom(CPU) to the top (MPU) of the 6 foot backplane
but keeping 32 parallel bits in sync. We had so many errors that we had to
design a repeater in the center of the backplane to re-sync the bits. The
challenges of keeping parallel data in sync in a copper medium is why
parallel SCSI and IDE hard drives were jettisoned for high speed serial.
With present technology it's easier, cheaper and more reliable to use ultra
fast serial rather than slower 32 or 64 bit wide parallel busses to achieve
the same effective data rate. This is another one of those real world things
that the casual bystander finds hard or refuses to believe. The fact that
serial is better that parallel is not intuitive but true.

Ralph DiMola
IT Director
Evergreen Information Services
rdimola at evergreeninfo.net

-----Original Message-----
From: use-livecode [mailto:use-livecode-bounces at lists.runrev.com] On Behalf
Of Mark Wieder via use-livecode
Sent: Friday, May 03, 2019 9:47 PM
To: use-livecode at lists.runrev.com
Cc: Mark Wieder
Subject: How big is a nanosecond?

https://www.youtube.com/watch?v=JEpsKnWZrJ8

-- 
  Mark Wieder
  ahsoftware at gmail.com

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