I'm resurrecting an old thread here. Sorry I'd missed out on the discussion a few months back.
Here's an image of two NEC PC-8300 main system ROMs: http://i133.photobucket.com/albums/q53/gweber68/NEC8300_ROMs_zps0vvxkcxv.png Maybe the numbers yield something useful? I can definitely confirm that the 8300 does have four 32K images that are bank switched, and my understanding is this: Bank 1: Base 8300 32K image Bank 2 & 3: Extensions to the internal applications, both TEXT & TELCOM (w/Xmodem) enhancements. Bank 4: An 8201A 32K image for 100% compatibility mode I've only ever been able to burn a 27C512 (for two 32K images) as a replacement system ROM, using the appropriate OUT command to switch between two images. However, I've not ever been able to reproduce the full 128K image using any sort of chip (including a 27C1001 as others have noted). I'm willing to bet though that a 27C1001 could be used with an adapter board of some kind but am lost as to figure out how to go further with that idea. Happy 4th of July everyone! Gary Weber web8201.net On Tue, Jul 4, 2017 at 2:19 PM, Gary Weber <[email protected]> wrote: > NOTE: The picture included two different system ROMs pulled from > different 8300s. Included both because the numbers on the chips are > slightly different, to my bewilderment. (Different releases I guess?) > > > On Tue, Jul 4, 2017 at 2:18 PM, Gary Weber <[email protected]> wrote: > >> I'm resurrecting an old thread here. Sorry I'd missed out on the >> discussion a few months back. >> >> Attached is an image of two NEC PC-8300 main system ROMs. Maybe the >> numbers yield something useful? I can definitely confirm that the 8300 >> does have four 32K images that are bank switched, and my understanding is >> this: >> Bank 1: Base 8300 32K image >> Bank 2 & 3: Extensions to the internal applications, both TEXT & TELCOM >> (w/Xmodem) enhancements. >> Bank 4: An 8201A 32K image for 100% compatibility mode >> >> I've only ever been able to burn a 27C512 (for two 32K images) as a >> replacement system ROM, using the appropriate OUT command to switch between >> two images. However, I've not ever been able to reproduce the full 128K >> image using any sort of chip (including a 27C1001 as others have noted). >> I'm willing to bet though that a 27C1001 could be used with an adapter >> board of some kind but am lost as to figure out how to go further with that >> idea. >> >> Happy 4th of July everyone! >> >> Gary Weber >> web8201.net >> >> >> >> >> On Sun, Feb 19, 2017 at 9:20 AM, 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. >>> >>> >> >
