Re: Arrrrrrrgggg!

[Chris Albertson <chrisalbertson90278@yahoo.com>]

Tom Droege wrote:
> 
> Chris and all,
> 
> I think there is little chance of using a standard interface.  The way the
> Mark IV was designed, there is no way to stop the scan once it has
> started.   Everyone seems to be ignoring this.
> 
> THERE IS NO WAY TO STOP THE SCAN ONCE IT HAS STARTED
> THERE IS NO WAY TO STOP THE SCAN ONCE IT HAS STARTED
> THERE IS NO WAY TO STOP THE SCAN ONCE IT HAS STARTED
> THERE IS NO WAY TO STOP THE SCAN ONCE IT HAS STARTED
> THERE IS NO WAY TO STOP THE SCAN ONCE IT HAS STARTED

Don't worry.  Playing back an audio CD on your stereo has the same 
problem.  You can't stop the bit stream going to the DAC or the
listener will hear a glitch.  Still the reader can go back and re-read
a bad sector if the ECC failed.  Data is buffered and the reader
is much faster then require so it can go back and do a re-read.

Same goes for butting pixels over Ethernet.  To pixel rate is so
slow compared the Eithernet (3.2Mbps vs 100Mbps) that there is time
to re-sent the data four times if required.  This is why "VOIP"
(Voice Over Internet Protocal) works.  The Internet has so much
more bandwidth then is required for compressed voice that the
non-deterministic routing of packetized data does not matter.

As I said "what a difference a decimal point makes."  Now the 
bottle neck is in the data generation, most likely the ADC chip.
Good.

Modern PCs are fast.  Look at the IDE disk interface.  In PIO
mode the CPU has to wait on a ready bit then stuff one byte
into a port.  Worse then driving a parallel port.  Still even
a slow PC can do this at 66 million bytes per second and still
track the mouse, download stuff from the modem and read the 
keyboard.  Pentiums can actually issue more then one instruction
per clock cycle.  New ones run at 1Ghz.


--
   Chris Albertson             
   chrisalbertson90278@yahoo.com
   Redondo Beach, California
   home: 310-376-1029
   cell: 310-990-7550