Getting a TF536 working on my Mega ST.

[PhilC]

@exxos ok will check tomorrow Nd will also jumper R150 as I forgot

I have a feeling this ram is also causing problems. My Pak68/3 wouldn't run on this Mega ST because of it.

[WiseGreasyBastard]

The TF536 now gets to desktop and the mouse works etc but bombs after about a minute. Next up is to try it with EmuTOS and different cpus just in case.

Good progress

Is this tf536 the one with 128mb on board?

My first tf536 has 128mb and with a 68EC030RP40 in a Rev 5 mega I get the rom read, 50hz init and stable white screen with bombs for bus error.
I'm not sure if my EC030 is good, It's one I have had in a drawer for at least a decade. I'm waiting on an 030 with MMU to arrive...

I'm following your journey whilst I wait.

[PhilC]

@WiseGreasyBastard this one is a 64mb one, i just grabbed the first one off the pile so to speak.

Try some capacitance on the clock signal and see if that helps but youll also need to change the bus SILs to 2.2k first though.

Need to get my floppy working as its decided to die, so will park this for a day or so whilst I decide what I'm doing with the ram etc.

[WiseGreasyBastard]

Try some capacitance on the clock signal and see if that helps but youll also need to change the bus SILs to 2.2k first though.

I have changed the SILs, dealt with a few mainboard electrolytics and have refurbed the PSU. I did quickly try pull a pull up and cap on the clock but no real change observed. I'll put another tf536 together when the processor arrives and test some more. Everything boots perfectly if I put the original 68000 back in.

Need to get my floppy working as its decided to die, so will park this for a day or so whilst I decide what I'm doing with the ram etc.

Hopefully that can be resurrected. Replacements aren't as plentiful as they once were.

[PhilC]

@WiseGreasyBastard i think its more likely a failed dma chip or something, will just take a bit of tracking down.

[DoG]

Tested the board on another Mega 1 with stock 100ns memory, although I have changed some of the ram chips for 80ns since they where broken. Otherwise all is pretty much the same as the other Mega 1. IMP on both Shifter and DMA on this one as well but without the 4,5V fix on them.

The TF536 worked on this one and produced similar specs in GemBench as the other Mega 1.

What kind of PSU do you use on yours? You use the IDE board that exxos and Icky did right? What speed on the rom is it?

[PhilC]

@DoG im using the decoder board that exxos made and a 70ns rom in an adaptor on the motherboard.

I remember talking with Pakman about this Mega and he mentioned 120ns is too slow.

The psu is a recapped dsp508y if i remember. Steady voltage out.

I have an exxos 4mb ram adaptor which I will try and that will rule things out.

[exxos]

I remember talking with Pakman about this Mega and he mentioned 120ns is too slow.

It can't be respecting DTACK timings if it needs faster RAM. I did try speeding up DRAM access on a booster (with 70ns DRAM) and it can't be done. There must be something else going on there.

[PhilC]

I don't know why I didn't try this before But the TF536 I was using to text the Mega has developed a fault. Unfortunately I only found this out by trying a different board.

So I'm happy to report that with a 100pf cap on CLK to GND and a 1k pullup on CLK as well and we are good to go.

Just running Gembench a few times

[Icky]

Glad you got it working @PhilC