Re: TI 990/189 debugging

2016-12-31 Thread Glen Slick
On Fri, Dec 30, 2016 at 6:53 PM, Josh Dersch wrote: > Just to bring some closure to this old thread, I finally picked up a > working TMS9980 cpu chip (after getting one faulty one off of eBay -- it > was even more dead than the one it was replacing). And it appears to work >

Re: TI 990/189 debugging

2016-12-31 Thread Eric Smith
On Fri, Dec 30, 2016 at 7:53 PM, Josh Dersch wrote: > Just to bring some closure to this old thread, I finally picked up a > working TMS9980 cpu chip (after getting one faulty one off of eBay -- it > was even more dead than the one it was replacing). And it appears to work >

Re: TI 990/189 debugging

2016-12-30 Thread Josh Dersch
Just to bring some closure to this old thread, I finally picked up a working TMS9980 cpu chip (after getting one faulty one off of eBay -- it was even more dead than the one it was replacing). And it appears to work properly in the 990/189 board, with the 9.3V supplied on the CPU socket. Thanks,

Re: TI 990/189 debugging

2016-11-17 Thread Eric Smith
9.3V might actually work fine for a TMS9980, even though it's below spec. It's not going to damage the part, so it may be worth a try before modifying the board for 12V to the CPU socket. In NMOS digital parts that predate depletion loads, Vdd needs to be significantly higher than the most

TI 990/189 debugging

2016-11-16 Thread Josh Dersch
Hi all -- Got myself a TI-990/189 single-board computer based around the TMS9980 microprocessor (actually, a variant of it, the MP9529, which apparently differs only in that it has a lower maximum clock and only requires Vdd of 9.3V or so...) It was advertised as "it looks like it's