here is a list of changes i made since using the sb180.
1. i re-designed the board to bring out the full potential of the hitach part.
my new board utilizes a fully buffered buss, with enough drive ability
to support 2 meg worth of ram.
this ram is configured as one "fixed" block of 256k with seven blocks
of mapped 256kb. I did it like this to allow easy control by a ram disc
driver. the code for implementing this consists of very minor mods
to Joe Wright's bios code. by the way, it is zero-wait state memory and
removing the one hardware-forced wait in the SB180 yields a %25 speed
improvement. I also made use of all the available 232 terms so that
DCD and CTS arent sharing chips. oh yes, the board is one inch wider
then the original sb180 pca and only the first 512kb is on the board.
those new 256k dram in "zip packs" would allow 1 meg on the pca.
2. on screen clock, updated every sec. does not interfere with graphics/
windowing software. this was a pain to set up and hogged up some space!
3. on screen modem status. (i often forgot to disc. the modem, my wife
didnt like it when the modem answered the in-law's calls).
Tcap support for the "host message line" provided by terminals would make
the implementation of these features (2,3) terminal independant. Oh well.
4. Separate recv,send,disc, status test, port-setup, and terminal routines.
no dialer cause i dont have an autodialer. Standard Christenson
protocol (CRC+CSUM) supported. Interrupt driven recv buffering.
5. mappable rom space. boot rom mapped out after boot load (even .5meg
system has 448kb ram disc). secondary romspace mappable on 16k bounds
throughout first 128k. rom is directly accessable as disk file.
6. recorder iop implemented. I just couldnt see paying $40.
the actual code for this is already on this system as DISCIOP.Z80.
you can "plug this code segment into EDI CRAMP's sysiop and your all set!
7. hardware rtc (nat 58274) utilized. TIMESTMP program used to timestamp
source files with yr/mo/da hh/mm/ss am/pm rev. (battery backed too)
8. modified config to allow parity control on async ports.
9. modified bios to support illegal op trap.
10.added parallel modem/console for remote use
11.warm boots are now done out of ram disc. this costs 2k and another
revision to mdsk.*****this mod is really the hot setup!*****************
12. i also altered the "break fix" so the console buffer is flushed. ever
get stuck with a buffer full of commands? with this they can be flushed.
