[Coco] General Memory Question about speed

[Mark McDougall]

Dave R in Illinois wrote:

> So If I understand correctly, faster memory would help a tad with simple
> calculations but when it comes to anything being drawn on screen, the
> GIME is the limiting factor, not the ram. 

No, that is not correct. The system clock determines the speed of the entire 
system and faster RAM will do nothing to alter that.

In the case of the Coco, as Gene has pointed out, the dot clock is 
considered the 'system clock' and all other clocks are derived from this (in 
early machines the 'system clock' was generally the video clock because it 
allowed a simpler design for interleaving video and CPU access to shared RAM).

The 6809 has a synchronous bus, which means devices such as memory are given 
a fixed time to respond to access requests. Using faster RAM gains you 
nothing because the CPU works in fixed-length clock cycles and hence a read 
from RAM, for example, takes 280ns even if the memory can present data on 
the bus within 90ns.

You may be interested in Sockmaster's "overclocking" project...
<http://www.axess.com/twilight/sock/4mhzproj.html>

Regards,

-- 
|              Mark McDougall                | "Electrical Engineers do it
|  <http://members.iinet.net.au/~msmcdoug>   |   with less resistance!"