Re: Thanks for the Verilog help

From: Jim Brain <brain_at_jbrain.com>
Date: Sun, 15 Dec 2013 10:24:10 -0600
Message-ID: <52ADD7AA.2030706@jbrain.com>
On 12/15/2013 6:32 AM, silverdr@wfmh.org.pl wrote:
> On 2013-12-14, at 21:49, Jim Brain <brain@jbrain.com> wrote:
>
> Really? I didnít think us to be in such frequency range here so that it would matter that much.
CMD cautioned many times about SuperCPU usage on the SX.  Mine worked, 
but that was to across the board.  I'm sure some of it is no doubt hurt 
by the fact that the expansion port drives through 3 circuit boards, 1 
ribbon cable, 3 connectors, and adds 8 inches of travel path to the 
unbuffered expansion port signals.
>> and EasyFlash and a lot of the newer cart options (Chameleon, 1541U, etc.) won't work when doing things that require tight timing.  If you could turn the EF3 KERNAL replacement function off, I bet the EF portion would work, and 1541U no doubt works as long as the function you are requesting does not require tight timing.
> I donít have the Chameleon (tried to put my hands on one for some time) but 1541U-II works well in the very same machine. I mean the KERNAL replacement function, which is the most timing critical AFAIU.
Without looking at the differences, I cannot explain that.
>
>> It's the cable, pretty much.  I bet if you pulled the case, and ordered a shielded ribbon cable (or better, created a non ribbon cable option), the problem would disappear.
> Pardon the ignorance but whatís so wrong with the ribbon at the frequencies we deal here with? Or - generally - with the ribbon. How much it differs from e. g. traces running parallel across the big C64 PCB? What with the (even longer) ribbon used for the USER PORT in SX-64?
Well, I think it's probably no worse than an 8" cart expander with 
parallel lines, and most such carts won't work if I attach them to 2 
X-Panders in series and use the last slot on the second XPander. That's 
not a completely fair test per se, but I think the cross talk of those 
lines would wreak havoc no matter what tech was used.

Jim

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Received on 2013-12-15 17:00:05

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