I keep trying to attach photos to this post thinking I can make them small enough. I *swear* I keep saving them as a 57k JPG but when I upload it, they're 200k and get rejected. Okay, let's try this a different way! Just embedded links this time...
Okay, here's what I found in the NEC PC-8300 Technical Reference, and right there in plain sight, all is revealed: http://i133.photobucket.com/albums/q53/gweber68/NEC_PC-8300_ROM_Bank_Select_zpsfnltzdo7.jpg The 128k mask PROM is the NEC uPD23C1000A. And here's the datasheet on the part itself: http://www.datasheet4u.com/datasheet-pdf/NECElectronics/UPD23C1000A/pdf.php?id=539613 Seems putting a new NEC PC-8300 ROM together might be within reach, for those so inclined. :) Gary On Sun, Feb 19, 2017 at 1:12 PM, Stephen Adolph <[email protected]> wrote: > yah, thx. I think it needs to be buzzed out a bit to confirm the > actual pinout... > > On Sun, Feb 19, 2017 at 12:20 PM, Kurt McCullum <[email protected]> > wrote: > > Steve, > > > > Keep in mind that I am guessing on the PROM based on the limited number > of 128k 28 pin PROMs available at that time. That's a pinout for the NEC > PROM but I don't know if that is the actual part which was used. There > should be a number on the chip that may lead to the answer. > > > > Kurt > > > > -----Original Message----- > > From: M100 [mailto:[email protected]] On Behalf Of > Stephen Adolph > > Sent: Sunday, February 19, 2017 5:13 AM > > To: Model 100 Discussion <[email protected]> > > Subject: Re: [M100] Parts for an NEC PC-8300 > > > > .. comparing a 27C1001 pinout to the one from Kurt, it looks like it may > just be possible to stuff a 27C1001 and wire up only a couple of signals. > > > > > > On Sat, Feb 18, 2017 at 8:12 PM, Stephen Adolph <[email protected]> > wrote: > >> come to think of it, you could probably tie /CE and /OE together. > >> > >> On Sat, Feb 18, 2017 at 8:08 PM, Stephen Adolph <[email protected]> > wrote: > >>> I did not grasp how much information is in that 500MB tech reference > >>> doc for the 8300. Wow! > >>> > >>> probably the best documented Model T. > >>> > >>> It is clear that the ROM is 128KB, and I think it is also clear that > >>> without some custom solution, one can't make a replacement main rom > >>> for the 8300 easily. At best you might be able to program a 27C1001, > >>> and then do a custom adapter board. > >>> > >>> A normal eeprom needs both a chip select and an output enable, so > >>> some extra logic might be needed too. > > >
