Thursday 13 July 2017


Finally got the STE booster powered by a Altera chip! For those not keeping up, I have moved away from "Coding" PLD's to drawing circuits instead.  The Altera IC is a copy of my STE booster design (which uses a 22V10 GAL) only the GAL was coded, the Altera is "drawn".

My first attempt failed..

Though things were not as they appeared to be.

This is again a problem relating to parity simms. Foolish me, I grabbed a set "close to hand" as I had been testing simms in that particualr STE, so wasn't any in it.  I managed to boot at 16MHz, though I had a read error on my floppy drive. I was moving it about and the STE started running perfectly. Odd! Incidentally, the same simms work fine on a stock 8mhz setup.

Turns out the 16MHz wire when going near the simms caused it to go into melt down. In fact even 2 inches away was enough to cause issues.  Removing the parity simms for my own simms and there was no issuses, regardless of where the 16MHz wire was!

A video of it failing can be found on my chan here

I had to make some small circuit changes as well with the booster logic. Oddly the same changes in the Atmel PLD caused slow downs.  Though in the Altera it just went from being stable to very unstable.  GB6 benchmarks matched what I had on my site as test speeds using the original GAL logic so everything is running perfectly as it should now :)

Another odd side-effect was I had to put a small SMT buffer on the STE booster PCB to clean up the GAL's output.  Now with the Altera , the signal was actually better without the SMT buffer!  In fact I even took out the 56R resistor I had to the CPU clock.

Overall, so far, its a big thumbs up for Altera.  Things so far work a lot better. It also proves I have got the hang of Altera's design software :)

Next up "to do", is to move to the 3.3V core version. The 5V one is basically obsolete now, but the 3V core still seems to be in production.  This basically means the whole IC runs on 3.3V, but it can accept 5V inputs.  This will make it really easy to interface to 3.3V SRAM and other stuff needing 3.3V.

After looking at the Altera devices, the 7000 series become really expensive for a larger IO device. Looking some more, the MAX II series seem to be a reasonable price and offer good IO interfacing.

It's only available in TQFN100 type packages, so a PCB will have to be done to test it out driving ROM and SRAM. 

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