What are the two larger sockets used for? Ray
Sent from my Verizon, Samsung Galaxy smartphone Get Outlook for Android<https://aka.ms/AAb9ysg> ________________________________ From: cctalk <cctalk-boun...@classiccmp.org> on behalf of Alexandre Souza via cctalk <cctalk@classiccmp.org> Sent: Wednesday, August 25, 2021 4:30:40 PM To: Eric Smith <space...@gmail.com>; General Discussion: On-Topic and Off-Topic Posts <cctalk@classiccmp.org> Subject: Re: Prototype new Apple /// memory board Eric, you could have used the 512KB sram chip instead of 4 128KB ones... ---8<---Corte aqui---8<--- http://www.tabajara-labs.blogspot.com http://www.tabalabs.com.br ---8<---Corte aqui---8<--- Em qua., 25 de ago. de 2021 às 17:28, Eric Smith via cctalk < cctalk@classiccmp.org> escreveu: > I've been working on a new memory board for the Apple ///, using (somewhat) > modern and still-in-production components, especially CMOS static RAM > rather than DRAM. Last night I soldered the connectors, sockets, and > passives of my first prototype: > > https://flickr.com/photos/_brouhaha_/albums/72157719738576267 > > I need to do some testing for shorts, etc. before I attempt to actually use > it in an Apple ///. I expect that some debugging of the design will be > required. > > The Apple /// design is _much_ more complex that the Apple II and IIe. I > intended this board to provide 512KiB of RAM, but I've already determined > that some design changes will be required for that, so this prototype will > only support 256KiB. > > The early Apple /// design, as documented in US patents, would have > supported up to 512KiB of RAM, but the actual shipped design reduced that > to 256KiB. There was a third-party 512Kib emory board from "On Three", > which required pulling various chips from the motherboard and running > cables from those to the memory board. > > The SOS operating system, as shipped, only supported 256KiB. On Three > modified the SOS bootloader to detect and use 512KiB. Some Apple /// > application software also had trouble with 512KiB, and On Three patched > some of those. >
