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Looking to purchase 1200xl w/U1MB installed

1200xl U1MB

4 replies to this topic

#1 Frankie OFFLINE  

Frankie

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Posted Wed Sep 23, 2015 9:21 AM

If anyone has one they are willing to sell, please drop me a line. I haven't had much luck getting mine working. Everything seemed to be ok for a little while. 1UMB working correctly. Now I'm stuck with a dark-green screen upon startup. Nothing seems to change that. 

 

So I'm opting for a pre-built one if someone is willing to part with it.

The more upgrades the better.

 

Frank

 

------------------------------------------------------------------------------

UPDATE:

 

I took my U1MB out of my 1200XL and put it in an 800xl. It worked fine. I reflashed it back to original (I had upgraded to the latest BIOS). Booted back up, was working normal.

Plugged in back into my 1200XL and it started working fine.

 

I think I'll wait on the new BIOS for the 1200XL's right now.


Edited by Frankie, Wed Sep 23, 2015 10:10 AM.


#2 flashjazzcat OFFLINE  

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Posted Wed Sep 23, 2015 10:18 AM

You won't see better results once the new BIOS comes out of beta. It simply reveals weaknesses in the hardware installation that the original BIOS overlooks. It's proved rather good at highlighting instability so far. All machines on which it failed were eventually found to be faulty. ;)

Edited by flashjazzcat, Wed Sep 23, 2015 10:20 AM.


#3 Kyle22 OFFLINE  

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Posted Wed Sep 23, 2015 10:39 AM

You won't see better results once the new BIOS comes out of beta. It simply reveals weaknesses in the hardware installation that the original BIOS overlooks. It's proved rather good at highlighting instability so far. All machines on which it failed were eventually found to be faulty. ;)

or the weakness of the person attempting the flash.  That was my case. :)



#4 Frankie OFFLINE  

Frankie

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Posted Wed Sep 23, 2015 1:02 PM

You won't see better results once the new BIOS comes out of beta. It simply reveals weaknesses in the hardware installation that the original BIOS overlooks. It's proved rather good at highlighting instability so far. All machines on which it failed were eventually found to be faulty. ;)

 

Would you be able to point me in a direction? Some things the original BIOS overlooks that the new one doesn't? 



#5 flashjazzcat OFFLINE  

flashjazzcat

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Posted Wed Sep 23, 2015 1:14 PM

 

Would you be able to point me in a direction? Some things the original BIOS overlooks that the new one doesn't? 

 

It would take someone skilled in the operation of a scope to go into great detail, but most problems so far reported (and eventually fixed) concerned the old chestnut: Phi2 timing. Symptoms included display corruption bad SPI transfers (setting the clock, etc). I had speculated regarding dodgy address lines, which would also cause issues. The only reason the original BIOS was discrepant in this respect is not because of any shortcomings, but because of different behaviours. The old BIOS does not make any attempt to set the RTC from code in ROM, for example. The new BIOS also uses a lot more (and tighter) non-maskable interrupts. At least the owners of the problem hardware since fixed are now in possession of stable machines: better to discover instability following a BIOS update than when encountering sporadic issues later on. I await reports of a crash on a stable machine.

 

Additional info: I also found one machine (my own) on which the Ultimate 1MB hardware coldstart bit was unreliable. This caused the machine to think it was warm-booting on cold power up, and was definitively fixed by the addition of magic bytes as an extra sense-check. In the original BIOS, a misread cold start bit was usually non-fatal. In the new BIOS, it caused problems. Again, this is likely down to Phi2 timings (at least that was the only thing we could speculate on when trying to diagnose the issue).


Edited by flashjazzcat, Wed Sep 23, 2015 1:20 PM.






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