How big is a nanosecond?

Stephen Barncard stephen at barncard.com
Sun May 5 15:58:56 EDT 2019


I always wondered about that. This is a revelation for me. I still remember
SASI and SCSI drives, And the switch to serial methods puzzled me. Of
course it’s more convenient.

On Sun, May 5, 2019 at 10:37 Ralph DiMola via use-livecode <
use-livecode at lists.runrev.com> wrote:

> 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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-- 
--
Stephen Barncard - Sebastopol Ca. USA -
mixstream.org



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