Looks like it might be the same idea as 64Kb ROMs vs. EPROMS; most of the ROMs used in arcade machines, lots of Commodore models and even the IBM PC were 24 pins whereas the 'normal' 64Kb EPROMs were 28 pins with the exception of one Motorola part; a simple adapter took care of the problem.
Anybody know how to get in touch with Gary Weber? He'd know, and also be able to make a stock ROM. m ----- Original Message ----- From: "Stephen Adolph" <[email protected]> To: "Model 100 Discussion" <[email protected]> Sent: Friday, February 17, 2017 8:26 PM Subject: Re: [M100] Parts for an NEC PC-8300 > VT simulates it with 4 rom banks. > so, .. it must be 128kB. > > I just have no idea what the pin assignment on a 28 pin socket could be. > > ..Steve > > > On Fri, Feb 17, 2017 at 8:20 PM, Stephen Adolph <[email protected]> wrote: >> ROM0 is 28 pins. I went downstairs to open it up again and count... >> can't be 27c1001. that's 32 pins as you say Mike. >> >> so, still a mystery. >> >> I thought maybe it could just be a 64k ROM - that clearly can fit in a >> 28pin socket. >> >> Steve >> >> >> On Fri, Feb 17, 2017 at 8:13 PM, Stephen Adolph <[email protected]> wrote: >>> oh that's very interesting. ok. I wonder what the pin assignment is. >>> >>> what does the 8300 need 96k of rom for 8300 mode for, vs only 32k rom for >>> 8201? >>> >>> a schematic would be golden. All I can say is there is no other ROM >>> on the board. >>> >>> Steve >>> >>> On Fri, Feb 17, 2017 at 6:51 PM, Kurt McCullum <[email protected]> >>> wrote: >>>> I don't have an 8300 here but web8201.net has some detailed technical >>>> docs. Here is a page describing the PROM as 128k >>>> >>>> http://web8201.net/NEC8201emulation.asp >>>> >>>> Kurt >>>> >>>> -----Original Message----- >>>> From: M100 [mailto:[email protected]] On Behalf Of Stephen >>>> Adolph >>>> Sent: Friday, February 17, 2017 2:53 PM >>>> To: Model 100 Discussion <[email protected]> >>>> Subject: Re: [M100] Parts for an NEC PC-8300 >>>> >>>> from my perspective- >>>> >>>> * there is a single socket ROM0 for the main ROM >>>> * ROM1 is for option roms. >>>> * there is no other ROM in the unit. >>>> * it is a 32pin socket, and so it must be no larger than a 64kB rom. >>>> Not likely to be 32kB. >>>> * i'd bet that OUT163,2 sets A15 on the socket. >>>> * no idea what the pinout is but it could be deduced quickly. I think >>>> since the PC8201 uses normal pinouts, so too does the 8300. >>>> >>>> So my bet would be a 27C512 would do it. It is possible however that it >>>> is still just a 32kB rom. Perhaps OUT163,2 sets a signal on the PIO or >>>> otherwise that the processor can check, to decide what mode it should be >>>> in. >>>> >>>> Steve >>>> >>>> >>>> >>>> On Fri, Feb 17, 2017 at 4:19 PM, Frederick Whitaker >>>> <[email protected]> wrote: >>>>> Mike >>>>> >>>>> There are places for two ROMS. In the regular PC-8300 there is only >>>>> one ROM used for Basic. >>>>> 83100 - 438 >>>>> N83A Basic >>>>> 1986 >>>>> Microsoft >>>>> 8649 - Z69 >>>>> >>>>> In the other unit, which no longer has it's regular ROM, there are two >>>>> ROMs >>>>> D276256D-20 >>>>> D276256G-25 >>>>> >>>>> I hope this helps. On the PC-8300 there is a wide access on the back >>>>> with three screws. Only two ROM sockets are visible and usable without >>>>> dismantling the case. >>>>> >>>>> I hope this helps. >>>>> >>>>> Fred Whitaker >>>>> >>>>> >>>>> On 2/17/2017 2:15 PM, Mike Stein wrote: >>>>>> >>>>>> Looks like it's up to you, Fred: >>>>>> >>>>>> Can you open up the 8300 and tell us exactly how many and what kind >>>>>> of ROMs or EPROMs are in there, i.e. any labels and/or part numbers? >>>>>> >>>>>> Since at least one is custom firmware it's probably in an EPROM (as >>>>>> opposed to a ROM) and will probably have a standard number like 27C512. >>>>>> >>>>>> From what I've read it looks like there should be three 28-pin >>>>>> sockets with a 27C512 in two of them and the third one empty or with >>>>>> an Option ROM in it. >>>>>> >>>>>> Let me know what you find. >>>>>> >>>>>> m >>>>>> >>>>>> ----- Original Message ----- >>>>>> From: "Fred Whitaker" <[email protected]> >>>>>> To: "Model 100 Discussion" <[email protected]> >>>>>> Sent: Sunday, February 12, 2017 3:32 PM >>>>>> Subject: Re: [M100] Parts for an NEC PC-8300 >>>>>> >>>>>> >>>>>>> Mike >>>>>>> >>>>>>> I don't have an image. I don't know if the ROM you are referring to >>>>>>> will do the job. The 8300 ROM is bigger than the 8201, but I believe >>>>>>> it uses the same chip as the 8201. >>>>>>> >>>>>>> I was under the impression that someone had uploaded a copy of the >>>>>>> 8300 ROM contents, but I don't remember where or when. >>>>>>> >>>>>>> I could send you one of my ROMs, from another machine, but I don't >>>>>>> know if that would help. >>>>>>> >>>>>>> Fred Whitaker >>>>>>> >>>>>>> On 2/11/2017 7:48 PM, Mike Stein wrote: >>>>>>>> >>>>>>>> Hi Frederick, >>>>>>>> >>>>>>>> If you can send me or point me to an image of that ROM I can >>>>>>>> probably burn an EPROM for you, assuming it's a JEDEC-standard 27xxx >>>>>>>> type. >>>>>>>> >>>>>>>> m >>>>>>>> >>>>>>>> ----- Original Message ----- >>>>>>>> From: "Frederick Whitaker" <[email protected]> >>>>>>>> To: "Model 100 Discussion" <[email protected]> >>>>>>>> Sent: Saturday, February 11, 2017 6:27 PM >>>>>>>> Subject: [M100] Parts for an NEC PC-8300 >>>>>>>> >>>>>>>> >>>>>>>>> I am interested in a replacement keyboard for my NEC PC-8300. I >>>>>>>>> also need a new Main ROM, When I received this machine it had a >>>>>>>>> specialized ROM in it. It will not boot. >>>>>>>>> >>>>>>>>> If I had those two items I could use this machine. I have asked in >>>>>>>>> the past if anyone could make a main ROM for this machine but >>>>>>>>> never received an answer. >>>>>>>>> >>>>>>>>> Fred Whitaker >>>>> >>>>> >>>>
