[Coco] V.PAGE 46551 and 46552 drivers

[L. Curtis Boyle]

On Mon, 21 Jul 2008 22:35:30 -0600, George Ramsower  
<georgeramsower at gmail.com> wrote:

>
>  Thank you for being so kind with my stupidity. I was thinking of the  
> chips from another mfg that works better. I think they have five digits  
> in their nomenclature.
>
>  I need to look into the 6552 and see if it is pin compatible.
>  Perhaps I could just swap the chips if they are. .... assuming the  
> drivers will work on those.
>  Darn.. I still have about seven or eight of the 6551 chips left.
>
>  The OS9 drivers work good up to about 9600 with the 6551 chips. Faster  
> is always better!
>
> George
I am guessing you were probably thinking of the 16550/16650/16750 series  
(with FIFO's and 115kbaud... each higher number increased the size of the  
FIFO buffer, starting at 16 bytes with the 16550). Rick Ulland and others  
made boards for the Coco using these, which could handle much higher  
speeds because you would only get an IRQ once the buffer was full, and not  
every byte (the overhead for that is atrocious). I seem to recall that  
Gimix, on their 6809 system, actually had some serial cards with a 256  
byte buffer, which means the serial port could be read/written to as fast  
as a floppy controller, with very high speeds and low CPU overhead. They  
had DMA on top of that too, as well. I don't think a board that  
sophisticated was every made for the Coco, though... and probably would  
have been too expensive anyways.

-- 
L. Curtis Boyle