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 16/32 bit cpu for a late 1976 cpu. 
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Joined: Mon Oct 07, 2019 2:41 am
Posts: 255
Changed the Instruction set around to be more compact a few weeks ago, but software the required a some minor changes in input text formating. Now that I found the typo in the bootrap loader, things seem to work correctly now.
Still not sure if I want to impliment a simple virual memory system. as that makes a OS much more complex with
page faults and traps.
Ben.


Wed Feb 17, 2021 3:33 am

Joined: Mon Oct 07, 2019 2:41 am
Posts: 255
In the last week the FPGA software suddenly decided to build working hard ware again. I have new version of the 8/16/32 bit cpu, with 7 GP registers
and a PC. Addressing modes are R+,# indexed and direct addressing. indexed is 16bit offset, and direct is 512KB.
Hardware is up to 1 MB of ram and with a limited front panel addressing of the First and last 32kb or ram or prom.
No mmu at all. Simple IRQ service.
Data types are signed/unsigned byte and signed/unsigned half words and full words
Working now at FPGA emulation stage, the PCB layout to begin soon. 5 card set, ALU#1 ,ALU#2, Control card, front panel card/rom/io, memory card.
Using 22v10's about 25 IC's are needed for the control card. 50 IC's using rom's only and TTL decoding of microcode. 512 24 bit words of micro code
is used. 2901A's are used in the two alu cards.
16 bit bus/20 bit address lines. Two phase clock @ 5.33 mhz. Byte's sive program ~ 15 seconds. It almost meets my goal, for DOS ERA computer
in only that MMU is missing. It now just needs more software development, and text editor. XMODEM is planned for when a second serial port is addes added.
Ben.


Sun May 09, 2021 2:15 am
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