Call for final Elf99 design input

The key to the elf design was minimalism and low cost. Substituting a latch and LEDs for a binary display instead of the til311 is cheaper and more buildable. using modern cmos and rams help. The basic elf was far to minimal and frequently expanded to get desired functions. The basic design did not easily permit that as it didn't decode memory or IO addresses. The RCA VIP or the 18S020 Evaluation board allowed far more flexibility with relatively little more logic. Thei cost was they had some rom. The 18S020 board was 4k ram (1822s), two 1852 as parallel io ports, UT4 monitor rom (512bytes) and another 32bytes for monitor storage. It used Q and EF3 for TTY/RS232 and the bus was available with numerous decodes at the edge connector. It also had LEDs for data, address and processor status lines (binary). This is a reproducable design. UT4 fits in 512byts of a 2716, the rest of the ram can be done with byte wide parts. The 1852s can be kept and the rest were common 40xx series. With 4k of ram and UT4 (or similar) programs like PILOT, TinyBasic, or some of the other neat software with a terminal. A much simplifed machine using 1802, 2 1852, 2 4028, 2 4042, 1 62256, 1 2716 and 1 6116, some glue logic for reset, run, runp and the same serial scheme as 18S020 would give 32k of contigious ram, 2k-32byts in the things along with the .5k ut4 monitor. This would be a very useful system that could accomodate expansion for IO (more ram??????). Allison