External, it seems to work at 7 Mhz... But I guess if you measure a 7.12 Mhz Z80H, it
seems to work at less than 2 Mhz externally...
This is because the Von Neumann cycle and because the Z80 has no internal instruction
FIFO. So, per opcode cycle it takes four clock cycles.
This is just an idea I have about it, I haven't measured it yet...
I don't have a memory scope or a logic analyser at home. And the scope I have is
from 1966 and doesn't go beyond the 2 Mhz... :-( At least I got it for free!!!
Conclusion : The clock circuit at the Xin and Xout of the R800 works at 28 Mhz, and can
work at 40 Mhz. This does not say that the clock is or is not divided with four in the
R800.
Who is able to check this?
Greetings from Erik Maas
----------
From: Manuel Bilderbeek
Sent: Friday, June 19, 1998 3:21 PM
To: [EMAIL PROTECTED]
Subject: Re: Turbo R?
> On Thu, 18 Jun 1998, Antoni Burguera wrote:
>
> > But... I have read that R800 works at 28 MHz.
>
> I have heard this same rumour, but if I'm correct this means, that R800
> works with 7 MHz clock, but it is as fast as 28 MHz Z80.
But hasn't it an 28 MHz crystal? Because some people (like Erik Maas) have
made it run on 40 MHz, by replacing the oscillator-crystal... How can you
explain this? Is the 40 MHz not really 40 MHz?
Grtjs, Manuel
PS: MSX 4 EVER!
PPS: Visit my homepage at http://studs.sci.kun.nl:8888/manuelbi or
http://www.geocities.com/SiliconValley/Vista/2653/manuelind.html (mirror, only
use it when the other URL gives trouble (e.g. server offline))
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