[sdiy] Frozen DX7IID

[greg at gzifcak.net]

Hmm, to my novice brain that doesn't seem like it would cause the CPU to
lock up but I have no idea. It was working fine with the dead RAM chips in
it. I'm assuming that was the problem before because all functions worked
except saving, and the self-test indicated a RAM failure.

Thanks for the info.

> Hi Greg,
>
> On Thu, 21 Aug 2014, greg at gzifcak.net wrote:
>
>> I just replaced the RAM in my DX7II. I swapped the existing Toshiba
>> TC5564PL-15 chips for TC5564APL-15 since this is all I could find
>> available. I searched for info on the meaning of the suffix but
>> couldn't find anything.
>
> From a datasheet A/B comparison, the only difference I could immediately
> spot is the Output Data Hold Time tOH.
>
> For the APL part it's 20ns min, for the PL part however 30ns min.
>
> This is the APL datasheet:
>  	http://pdf.datasheetarchive.com/datasheetsmain/Datasheets-X2/DSA627000177.pdf
>
> And here's the 1983 databook including the PL part:
>  	http://bitsavers.informatik.uni-stuttgart.de/pdf/toshiba/_dataBooks/1983_Toshiba_MOS_Memory.pdf
>
> HTH,
>  	Rainer
>