MFX mass-storage add-on

Modern, Memotech inspired, hardware projects
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gunrock
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MFX mass-storage add-on

Post by gunrock »

Hope you didn't mind Dave, but I was excited to read about the forthcoming (perhaps) and (not-yet) imminent release of the MFX mass-storage option for our MTX machines, so I thought I'd create a placeholder thread for when there are more details out there.

I'm in the market for one (maybe two! - yes, I bought another MTX 512. Promise I'll update the hardware survey soon :lol: ). However, heeding your severe warning, I shan't ask about when it's ready or the mystery surprise functionality (lootboxes come to the MTX at last? You might have one that works, or one that works sometimes! :D )

For those wondering what this is all about, see here:

http://www.primrosebank.net/computers/m ... fx/mfx.htm
Steve G
Danish-keyed Memotech MTX 512, CFX II and loving it
Martin A
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Re: MFX mass-storage add-on

Post by Martin A »

Pleae don't get too excited. Yet.

Yes there is a prototype.

Yes the onboard memories work, so there's 512k ram and paged roms where the contolling software can go.

And there's a VGA test card display based on the 80 column board and a pre-loaded image.

At the moment that's all there is. The current focus is on getting reliable signals from the 5v 4mhz Z80 to and from the 3v 50mhz FPGA without damaging it. Having the VGA display is nice, but having it programmable would be nicer :)

Test builds of Andy's VHDL code for the VDP sugguest there should be no problems space wise fitting it into the FPGA we're using.

Other that that, I've not really looked at the SD card or the VDP or anything else yet. (being vague there so there's no premature disclosure of the super secret extras in case they never make it).

It a promising start, but only a start. Hence Dave's warnings about maybe Q3 or maybe never !
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gunrock
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Re: MFX mass-storage add-on

Post by gunrock »

No, no, I get it Martin. :D

Just wanted to draw out a few more tidbits from you both!

Is the chip shortage a factor, if you do finalise your design? I know the creator of the Ultimate 1541 products for the C64 has totally redesigned the (very stable) design of his successful product based purely on which parts (smaller FPGA for starters) he can source.
Steve G
Danish-keyed Memotech MTX 512, CFX II and loving it
Martin A
Posts: 594
Joined: 09 Nov 2013 21:03

Re: MFX mass-storage add-on

Post by Martin A »

The availability of chips is an issue. As is the availability of suitable dev boards. Hand soldering 144 pin TQFP packages is not my idea of fun, and those are about the "easiset" PFGA packages to work with. I don't even want to THINK about BGA parts! So something pre-assembled, giving access to sufficient I/O pins is a must.

The board I'm using however has one of the smaller FPGAs in terms of resources and I/O pins. If the design fits that it should also fit a larger chip if thats what chip availability demands we use. There is of course no point going too big on the FPGA dev board. The whole of the MTX hardware would fit in the DE10-nano of MiSTer fame. Attaching one to a real MTX just to do the VGA display would be silly.

Surprisingly another issue is the edge connectors. I can "bodge" fit 31 x 0.1" straight up connector to the 30x 0.1 internal connection for ptotoyping. However those connectors are designed for the old PC ISA slots. Finding a suitable horizontal rather vertical fit connector, that's in production, doesn't require a minimum order of 5000 or a 6 month to a year wait (or both) is not as easy as it might have been in the early 80's when the MTX was designed.
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Dave
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Re: MFX mass-storage add-on

Post by Dave »

On the connector issue . . . .

As Martin knows, I can get a suitable connector (I think), it has a MOQ of 25 but has an 18 week lead time. The connectors alone will require an up front investment of £150!

However, once we’re a little further down the road, I’ll bite the bullet and place an order, otherwise 3Q will soon turn into 4Q - or beyond!

Regards
Dave
Bill B
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Re: MFX mass-storage add-on

Post by Bill B »

Should you get around to placing an order for the connectors, I could have an interest in a few, irrespective of the progress on the MFX. Spread the cost / risk.
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Dave
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Re: MFX mass-storage add-on

Post by Dave »

Hi Bill,

thanks a lot - that's thoughtful of you. PM sent

regards
Dave
Martin A
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Re: MFX mass-storage add-on

Post by Martin A »

One step on from the test card, having cleared a couple of hurdles cause by lack of clear info on the PFGA dev board. The Rememotech CPM boot rom is generating a recognisable display on the VGA monitor.

Slightly worrying is the lack of "OK" after the memory test, and the monitor command to display the start of memory showing ROM contents and not RAM. So that's the next job.

Then I'll moving on to the SD card support. That again will be an import from ReMemotech.
Progress
Progress
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gunrock
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Re: MFX mass-storage add-on

Post by gunrock »

That's great progress, Martin!

Out of interest, do you have much FPGA experience?

I've had a look at some VHDL and whilst the logical notion of a virtual pin, clocks, ram refreshes etc. make sense to me, the actual configuring of gates to simulate hardware just melts my brain. It's so far from procedural or OO programming paradigms, it freak me out. Like in most code you write, concurrency is a special case and introduced with care, yet in FPGA programming every damn thing is concurrent! :shock:
Steve G
Danish-keyed Memotech MTX 512, CFX II and loving it
Martin A
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Joined: 09 Nov 2013 21:03

Re: MFX mass-storage add-on

Post by Martin A »

FPGA experience very little. All I've previously done in Quartus is VGA text displays using the big PLCC CPLDs that might have made a CFX3 if we'd kept going in that direction.

The step up from 128 macrocells to 4000+ logic elelments + memory etc is massive!
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