CURRENT PROTOTYPE STATUS (SEC 64MHz 68000)

[exxos]

Had to resolder the CPU as was a iffy joint somewhere.. but now running at 50MHz

as said previously, this is not much faster than 32MHz on the STE.. basically because the ROM IC itself is bottlenecked to 32MHz speeds. but there are things in the pipeline to overcome that limitation.. But more on that some other time..

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Next to plug this in and do the firmware & software to enabled it

These are 45ns SRAMs, so I doubt I will get past maybe 40MHz speeds with it.. but its a start...

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[exxos]

Iffy connections aside...

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[exxos]

Now I realise I have done something dumb , probably out of force of habit with only dealing with ROMs for the past 25 years..

I will leave this little puzzle here for everyone

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[stephen_usher]

The READ/WRITE is the wrong way around?

[olivier.jan]

With the RAM chip always enabled, how you prevent it being written when the CPU writes to other devices ?

[exxos]

With the RAM chip always enabled, how you prevent it being written when the CPU writes to other devices ?

[exxos]

Started a new SRAM board.. this one will be 3.3V only to speed things up with the PCB. Using 2 chips means I am 2 RAM OE lines free, so I can reuse them for the 2 missing CE lines...

Mouser only sell the chips it seems, almost £20 a pop, but still a lot cheaper than the 5V board. Also had to do a new lib for it

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[exxos]

Other than running DRC 500 times.. should be done..

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[exxos]

I've had a thought that I'll need some pull ups on the 4 control lines to 3.3v. As the SEC booster has to run on the 5v bus, I can't feed 5v into the SRAM lines.. So pull ups to 3.3v and open collector drive on the booster should fix the problem.

I hope to order these boards on Monday along with the SRAM. Once its all working , I will try and build a few for stock, though I'm not planning on making many of either as time and cost will be pretty high..plus the board will only work on the H5.. I do hope to move to SDRAM type board in the future. Though with things going at a snail pace all the time, I don't think that board will get done this year.

[exxos]

I've patched up the current SRAM board.. The chips are to slow for 50MHz+ speeds, so had to add some waitstates..

Considering the TF536 pushes around 800% without caches and is 32bit, It makes sense that a 68000 Can operate around 400% as its 16bit. Though I think once I get the new SRAM board built, I can easily run 64MHz. So 400%-500% speeds should really be reachable.

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I have had it also at 359% but this is only a quick patch up to see things are working as expected.