And yet another preview.
PS. The 16 bit computer nor windows ,has not crashed yet running the 99 bottles of beer program.
That is good sign that the 20 bit computer will work. I expect to have the ALU and memory board finished soon
as I have to tack on just the new bits, the old lay out is the same.

Finished the ALU card. Memory cycle is 1.6 uS. Repaced the
PAL with TTL.

A TTL CPU with core memory sounds awesome, do you have any PDF's of the circuit and block diagram we could have a look at ?

Sid

Sorry by it is just emulation, of core for timing. if core stacks were around it would be easy to interface as it is designed
around the read/write back memory cycle.


The best example may be the PDP-8 /E schematics.
They use a 20 MHZ clock to generate core timing logic. strobe here, pulse there, latch now.

The other two PCB's are out the door. Since a long weekend is coming up I will relax before summer ends.
I have all the parts, to build the PCB's for early September.

I got the hamsters running at full speed. Testing with 1.33 uS memory cycle.

Set the default speed to 1.5 uS, like the PDP 9/L (1969-1970)
Expected use of MSI TTL like the 74181 has the 16 bit cpu for late 1970
and the 20 bit cpu for 1971 release dates.

The SPI interface did not work, but I reprogrammed the 22v10 for a simple bit bang interface
with the 74hct299.The code now works to initialize the SD card, -1 no card 0 card.
Testing of a sector read/write is the next project. A greater than 4 Mhz clock is needed for it
to work. < 2.0 uS.