07-03-15 09:55 mark lewis wrote to Ed Vance about SCSI Adapter Startup

 ml> {at}MSGID: 
 ml> 02 Jul 15 11:05, you wrote to me:
Howdy! Again Mark,

 ml>> PATA (old style) and SATA (new style) are both IDE... IDE

 EV> I knew the P meant Parallel and the S meant Serial.
 EV> I didn't know both xATA HDD's were IDE.  Thanks!

 ml> welcome :)

 EV> I've always thought a Parallel connection was the way to go. I'm
 EV> thinking about back in the early days Printers were RS-232 Serial, but
 EV> later most all Printers used a Centronix Parallel connector. Until USB
 EV> came along.

 ml> yup... parallel requires "latch queues" so that each bit is
 ml> placed into a latch and held while the others are loaded into
 ml> their latches... then they are all released at once to travel
 ml> in parallel... loading the "latch queue" takes time and adds
 ml> some overhead... "latch queue" isn't what it was really called
 ml> but it is the closest thing i can think of right now...

 ml> think of parallel as the big toll booth line across the
 ml> highway... think of the highway leading up to the toll booth as
 ml> a single lane and the highway leaving the toll booth as a
 ml> multilane highway with as many lanes as there are booths... as
 ml> each vehicle approaches, they are directed to the first empty
 ml> booth on the right so they fill the booths from right to
 ml> left... they are held in the booth until all booths are full
 ml> and paid... then they are all released at the same time to
 ml> travel the next part of the highway in the lane they are
 ml> currently loaded in... there is no lane changing... when the
 ml> first group leave the booths, the next ones are queued in the
 ml> same fashion from right to left to pay and hold until all are
 ml> loaded and ready... that's how serial is converted to
 ml> parallel...

In my thinking about Dot Matrix Printers, I always thought Parallel
was faster because of seperate signal lines to each solenoid.
On every cycle the proper pins would go BANG! against the Ribbon to
make 'their' mark on the paper.

Serial Dot Matrix Printers would have to wait 8 cycles, plus maybe a
START and STOP cycle so the selected pins would move towards the paper.

Anyway that's my way of thinking about Serial versus Parallel.


... An unemployed Court Jester is nobody's fool.
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