TTL propeller

agimuhing

Just curious here

What would the specs be for a TTL propeller?

The current propeller is CMOS

Martin Hodge

The first thing that comes to mind is "kilowatts"

Mike Green

These days, I don't think anyone actually makes TTL (transistor-transistor) logic. There may be some for special applications and for repair of old systems. It takes a lot of power and chip area and is much slower than modern CMOS. In addition, there's CMOS logic that works with TTL logic levels (check out 74HCT parts). See this article.

Phil Pilgrim (PhiPi)

The reason TTL (and NMOS) chips are so power-hungry is that current has to keep flowing just to maintain a logic state. This is because the drivers are not complementary, i.e. they can only "pull" one direction against a current source. In CMOS logic, the drivers can both source and sink current so, except for leakage, current needs to flow only during state transitions in order to charge or discharge the internal MOSFET gates. This also explains why the current consumption of CMOS micros is more a function of clock speed than anything else.

-Phil

Cluso99

To give you some relativity to how many TTL packages you would require...
A minicomputer of the 70's had about 8 pcbs of 12"x12" full of TTL chips (74xx) to do the processor alone (no memory, no I/O, no disk or tape controller). The prop is more powerful and contains more memory than this mini could house. The power supply was a big switcher 12"x12"x24" and was probably 2400W. The disc drives consumed 2400W each (10MB) but took 4x2400W on startup to spin the platters up to 100MPH.

74xx TTL chips are likely still available. However, 74HCT (TTL compatible) would use significantly less power. 74LVC would be better still. 74xx top out at a few MHz whereas 74LVC will run near prop speed.

You would be much better using an FPGA where you could reconfigure and build using gates, but all in one package. A largish Xilinx Spartan 3 could do the trick and you can buy kits.