[Coco] Drivewire question

[Roger Taylor]

At 05:46 PM 3/25/2009, you wrote:
>On Wed, 25 Mar 2009, Darren A wrote:
>
>>On 3/25/09, Steven Hirsch wrote:
>>>
>>>I have some doubts about the 6551 being capable of 115.2k baud.  Even if
>>>the chip itself can do it, the expansion bus may prove to be a bottleneck.
>>---
>>
>>What do you mean by "expansion bus"?  Are you talking about the
>>cartridge port and/or MultiPak?
>>
>>There would certainly be no bottleneck there since data can traverse
>>the bus at a rate of at least 1 byte every cycle.  For 115.2k baud,
>>the CPU only needs to service the 6551 roughly once every 77 cycles
>>(not including any status polling).  The double density floppy
>>controllers have to transfer data at more than twice that speed (250
>>kbps).
>
>Granted, but I'm thinking of a case where you are reading from one 
>cartridge and writing to a device on the other.  From an electrical 
>point of view, you've just doubled the bandwidth demand.  Plus, 
>there's interrupt handling overhead and latency for the RS232 
>pack.  It will be interesting to see if that combination can keep up 
>with the bit-banger port + cartridge port (which, indeed, is an expansion bus).
>
>Steve

Thanks to how fast electricity is, you're not going to notice any 
difference between a properly-coded bitbanger, wired RS-232 Pak, or 
wireless RS-232 pak connection.  :)  :)  :)

My wireless pak is blazing along just as fast as the bitbanger code 
yet there's more stuff for the signals to pass through:
CoCo -> 6551 -> bluetooth module -> PC USB dongle -> PC serial drivers

Doesn't make a bit of difference.


-- 
Roger Taylor

http://www.wordofthedayonline.com