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8k BASIC

A project log for Novasaur CP/M TTL Retrocomputer

Retrocomputer built from TTL logic running CP/M with no CPU or ALU

alastair-hewittAlastair Hewitt 03/21/2022 at 03:490 Comments

The hope was to ship the Novasaur with some form of BASIC on board. There is just enough space on the B: drive to fit a 1970's era 8k BASIC. The more capable MBASIC 5.21 can be loaded to the A: drive, but at over 24k it won't ship in the ROM.

The initial effort was bringing up the original Microsoft Altair BASIC (circa 1978). There is a source code available, but this proved to be defective. The alternative was the IMSAI 8K Floating-point BASIC (circa 1977). This source code was more successful!

The image above shows the following BASIC program running at actual speed:

10 FOR X=0 TO 2*PI STEP PI/15
20 PRINT SPACE(INT(SIN(X)*36+36));"*"
30 NEXT X

There are still some optimizations to be made in terms of console integration and the software restarts. The performance isn't too bad though considering the CPU is running at 1/5th the speed of the original hardware.

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