Thanks for the update Andrew, if I could add, the 4MG “Over the top” memory board is just to test the concept and determine a circuit that will allow us to run that boards memory at a much faster clock speed to the one on the S-100 bus. The S100 bus will be a kind of reverse cash RAM running at low speed, configurable from 0 – 16MG. The idea is to actually have GB capacity pseudo static RAM and/or DRAM on the daughter board(s). Status here:-
Currently I am writing a Protected Mode 80386 Monitor. So nice to be working with non-segmented 32 bit code! Will update site page in a week or two.
S-100 80386 CPU board is doing another round of prototype build and test. This is the third prototype board which is feature complete including the “over the top” memory board.
S-100 80386 SRAM board is starting its first prototype build and test phase. This is the kick-off for the other side of the “over the top” memory connector basically to verify it works. This is a 4MB SRAM board and whether this actually results in a new board has not been determined. Linux and/or BSD operating systems generally need more than 4MB so this is the start of the design series of new boards not an end product.
S-100 VGA has a troubled history with several non-working prototypes. We did the ISA VGA derivative which worked resulting in many new insights of the GD5420 chipset. Unfortunately an updated S-100 VGA still didn’t work but I think we are going to try again with another new prototype soon.
S-100 VDP (V9938 + AY-3-8910) this prototype is on hold pending an update from the last build and test cycle. There are several updates that need to be done but I haven’t gotten to them yet. This is kind of a low priority project that gets worked on during slack periods. I am hoping to try again this summer. It has promise but is not urgent.
S-100 uPD7220 is kind of an interesting situation. This is a spin off design of a working ECB uPD7220 V2 GDC board but recast as an S-100 board. The design is complete as is the PCB however it has not gone through a build and test cycle to verify its functionality. Normally John and a few other builders do the build and test but his plate is pretty full with S-100 80386 and the S-100 VGA.
At the moment I think we have two options with the S-100 uPD7220 GDC board if we want to proceed with it: first, is to do a traditional small batch of prototype PCBs ($150 for 4) and spread out to some new builders for build and test prior to doing a production run; second, is to skip the usual prototype build and test cycle and go directly to a production board.
The second option is risky but partially mitigated in the two parts of the design are known working (the S-100 IO core and uPD7220 GDC) but not together as a unit. The S-100 uPD7220 GDC board offers a lot of potential in that it can generate VGA compatible video (640x480 and 800x600) at 16 colors (4 bit planes) but is not VGA register compatible.
So… what do we want to do with the S-100 uPD7220 GDC board? Ideas, thoughts, comments, questions, all welcome.
Thanks and have a nice day!