[Coco] Help with Nitros9 on SDC?

[Rocky Hill]

 Hi Don,
Maybe I missed it, but did you try the SDC on  another CoCo?I read through the posts but I didn't see any mention of that.
Assuming you didn't try it on another CoCo, here is my story.....

I had a very similar issue with my SDC randomly locking up my CoCo 3and occasionally displaying random characters. It was frustratingand it made me yell obscenities at my CoCo 3.
Most of the lockups I experienced where while launching the SDC explorer,Launching Nitros 9 EOU, or trying to run one of sockmasters demos.Occasionally my CoCo3 would crash when playing a game loaded from the SDC butRegular carts seemed to work just fine.

I wasn't totally surprised this was happening to me because I expected things to act funny as this was while I was testing a recreation of the CoCo 3 board. 
Relative to my new CoCo3 board, most of the evidence pointed to a faulty SDC butI knew the SDC was fine or at least fine enough because it didn't crash when usingit on an original CoCo 2 or CoCo 3. 
Through trial and error I did eventually figure it out andthe SDC no longer crashes when using it on the new CoCo 3 board. The culprit turned out to be a slight difference in the replacement PIAI was using for IC5. The number on the chip for IC5 is "LSC81001P"but it's "6821" compatible with some extra magic to make it safer when readingkeyboard presses.
WDC makes a drop in replacement for the 6821 and it is what I decided to useinstead of sourcing older PIA's. The part number is W65C21N6TPG-14.
I know that this is a bit of a stretch in your case but it might be worth a thinkso here are the two things that fixed the SDC's behavior on my new board.
1- I replaced the modern PIA with an older 6821. This of coarse was the easiestthing to do but it meant I had to use an older PIA.
2- I added a 4.7k pull-up resistor to the SELA line of the SC77526 DAC/ADCchip. This can be added to either pin 11 of IC7 or pin 39 of IC5.I didn't deduce this fix, I simply remembered that the CoCo 2 has a pull upresistor on the SELA line and since I had already zeroed in on thePIA as the culprit, I figured someone had a similar issue when designingthe CoCo 2 so I copied it and it worked.
I added option two to the latest board revision because it's a much better fixthat allows the board to work with older PIA's and the new replacement one.
Again, I know our situations are different and I'm not saying you should add a pull-up resistor but consider that the PIA might be misbehaving and at thevery least I think it might be worth a look around the PIA to make surethere isn't anything out of the ordinary.
That said, adding a pull up resistor with two clips is a really easy test thatwill not hurt anything. 4.7k, 10k, 47k any of those values should work.

I hope you get it figured out soon.

Pedro






    On Sunday, January 9, 2022, 05:00:11 PM EST, Don Barber <don at dgb3.net> wrote:  
 
 Hi folks, after giving up in frustration I've come back to look at this 
several months later. To jog memory: I was getting weird lockups trying 
to get NOS9 working and I was asked to try EOU. EOU Beta 5 boots for me, 
but Beta 6 and later fails to boot. Curtis looked at a video of my boot 
screen and pointed out Krnp2 did not load and asked if I'd modified the 
bootfiles (I had not, and confirmed with an md5sum of my disk image). 
All tests I run on my coco3 for memory, GIME, etc all come back as 
working fine.


So, back to it. I thought maybe if I could add in more debug statements 
here and there in the boot process, I could track down what was failing 
and where. To that end, I cloned the latest nos9 code tree from 
sourceforge (I just used the main branch...is there an EOU branch I'm 
not finding somewhere?), cross-compiled, it on Ubuntu Linux, and loaded 
it via drivewire. But lo and behold: everything seems to work fine as 
long as I stick to access just via DW.

But when I try to do anything involving the cocosdc, it seems to work 
for a second and then freeze up. For example, running just 'sdc' shows 
the file listing, but never returns to the prompt.

So...I'm starting to conclude that there is something wrong with my 
CocoSDC. I've tried different sdcards so I don't think thats it. Its 
weird that it seems to do everything with standard .dsk images I get 
from the Color Computer Archive just fine, but only acts weird in NOS9. 
But the SDC does seem to be the only common factor here.

As such, I have what may be an unusual request: may I borrow someone's 
known-working CocoSDC to see if the same behavior results? I will pay 
for shipping both ways.

Also, if anyone has any advice on getting the latest EOU 6.1 working 
purely via DW and not require a CocoSDC, that could be a good test too.

Thanks!

Don

On 4/30/21 11:58 PM, L. Curtis Boyle wrote:
> I am sorry, too… I am at a loss at this point. I am by no means a hardware expert. Hopefully someone who is can help.
>
> L. Curtis Boyle
> curtisboyle at sasktel.net
>
>
>
>> On Apr 30, 2021, at 9:54 PM, Don Barber <don at dgb3.net> wrote:
>>
>> No change in behavior. Appreciate the help.
>>
>> Don
>>
>> On 4/30/21 10:21 PM, L. Curtis Boyle wrote:
>>> If you hold down SHIFT when booting, does that make a difference?
>>>
>>> L. Curtis Boyle
>>> curtisboyle at sasktel.net
>>>
>>>
>>>
>>>> On Apr 30, 2021, at 8:10 PM, Don Barber <don at dgb3.net> wrote:
>>>>
>>>> Agree thats the simplest explanation, but I've tried 3-4 different 512k ram test software packages and they all come back as good.
>>>>
>>>> Don
>>>>
>>>> On 4/30/21 10:07 PM, L. Curtis Boyle wrote:
>>>>> Maybe some bad RAM, perhaps? The stock games (for the most part) will run in 128K, but EOU (since it preloads some things) definitely needs 512K.
>>>>>
>>>>> L. Curtis Boyle
>>>>> curtisboyle at sasktel.net
>

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