Subject: Re: [stella] Big Balls From: cwilkson@xxxxxxx Date: Wed, 24 Feb 1999 16:04:58 EST |
-------- In message <000a01be6033$eeb39e20$1002000a@light>, john@xxxxxxxxxxx writes: > >I'm still fascinated by the differences we've seen between different >machines. I keep wondering if the differences are caused by different >TIA chips, or some other timing anomoly inside the machine. Maybe the >clocking is slightly different, maybe skewed on one machine but not the >other. I wonder if anybody knows if there was really more than one >version of TIA chip? Or if maybe it's just because certain aspects of >the machine timing were "cleaned up" on later versions of VCS, like the >JR and 7800? I don't know about the TIA, but the clocks are different. Enough so that the clock may die on at least one version (I can't remember which). Bascially what I was doing was triggering my logic analyzer off of the clock. Just that little bit of added RC loading (C=10pF, R=10M) was enough to skew the clock beyond use. And if I remember right, I tried buffering the clock with a 74HC04, and just the loading from one CMOS inverter killed it in similar ways. And the clock skew was enough to prevent what I was trying to do anyway.... So yeah, I think the clocks could be flaky in some boards. Note that I mean *individual* boards, not all boards of a particular revision.... -Chris -- Archives (includes files) at http://www.biglist.com/lists/stella/archives/ Unsub & more at http://www.biglist.com/lists/stella/
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