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westfw

Quote
DOS is an OS.

DOS is a "program loader."
Not that that's a bad thing, nor does it disqualify it from being an "operating system."
If RPi is toggling a pin at 21MHz, that's without the linux operating system being involved.
Talking to IO in fast system is always slower than the internal cycle time.  Switching a pin at (relatively) high power at the edge of your circuitry and with a potentially significant load capacitance is "difficult."
(You also don't want to look too closely at how slow that RAM memory access is, on cache misses.)


GoForSmoke

IIRC it takes an 8080 2 to 4 cycles to do most anything and way more to do some things.

On a 6502 the same happens in 1 cycle. ... or 2.


I find it harder to express logic in English than in Code.
Sometimes an example says more than many times as many words.

JoeN


Quote
DOS is an OS.

DOS is a "program loader."
Not that that's a bad thing, nor does it disqualify it from being an "operating system."
If RPi is toggling a pin at 21MHz, that's without the linux operating system being involved.
Talking to IO in fast system is always slower than the internal cycle time.  Switching a pin at (relatively) high power at the edge of your circuitry and with a potentially significant load capacitance is "difficult."
(You also don't want to look too closely at how slow that RAM memory access is, on cache misses.)


OK, that is something I suspected and hoped was not true, but thanks for the information.  On the Atmel chips you can get a square wave at clock divided by four, 21Mhz on a 700Mhz system is clock divided by thirty three.  I was hoping that the Raspberry Pi was a cheap and simple route to working with higher throughput chips, like high-speed ADCs with parallel interfaces (e.g. 8 bit 100Msps), but I can see that was a pipe dream.  :(  I'd rather write code than figure out how to get a FPGA to work.
I have only come here seeking knowledge. Things they would not teach me of in college.

westfw

Quote
high-speed ADCs with parallel interfaces

You might be able to connect those via the memory interface, or via some sort of DMA scheme.  But you probably can't get 100MHz; that's only 10ns for each byte, which is down near the propagation delay for individual logic-gate chips...

GoForSmoke

What you do with the data is going to make a difference. Hope it's not high-res face or voice recognition.

I find it harder to express logic in English than in Code.
Sometimes an example says more than many times as many words.

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