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Old 26th Mar 2021, 10:34 pm   #261
Buzby123
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Default Re: I found it! A very sorry looking MK14.

I was interested in find out what this 'testability' is in these PROMs, anyone know ?
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Old 26th Mar 2021, 10:51 pm   #262
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Default Re: I found it! A very sorry looking MK14.

I've never seen that before - I presume it was in National Semiconductor documentation ?

And that it was all for their manufacturing tests, so you wouldn't really be able to do it yourself - Although it might be nice to be able to read these extra test fuses / even program some that weren't blown, to see how good an IC was before programming the data area.
I suppose they had a special test mode that they don't tell you how they entered, in order to do this.
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Old 26th Mar 2021, 11:19 pm   #263
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Default Re: I found it! A very sorry looking MK14.

And there's more !

Today I found in the attic a box with about 30 databooks that I've not seen for years. One of them I think is the same NatSemi Memory Data as linked to a couple of posts ago.

I just had a quick look in it, and page 11-82 looks very interesting.

We MK14 owners know two things. (1) SoC cut every corner possible, (2) the PROMs get @***ing HOT !.

It looks like NatSemi had this heating in mind, and suggested a way to reduce it dramatically. That's what's on page 11-82.

Have any of you seen these PROMs in commercial products, did they get this hot in those applications ?
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Old 26th Mar 2021, 11:33 pm   #264
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Default Re: I found it! A very sorry looking MK14.

They always run very, very hot, alarmingly so. Whenever I programme a set for anyone I always warn them about that because they could be forgiven for thinking they were faulty otherwise. I worked out once that the PROMS consume 2/5ths of the entire current drawn from +5V by a fully populated MK14. You could always try putting little heatsinks on them I suppose but that would give them a non-original appearance. I quite often see heatsinks added to Sinclair ULAs, another famously hot-headed series of ICs.

Just lately I experimented with pin-compatible PROMS from other manufacturers, first the N82S131 from Philips / Signetics which also runs quite warm, possibly not quite as hot as the Nat Semi devices.

Then more recently I bought a pair of the AMD 27S13As offered here on the forum by kan_turk and although they still warm up they don't seem to run anything like as hot as the Nat Semi devices. Tim has those now, but I don't imagine he will have run them for long enough to notice.
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Old 27th Mar 2021, 2:15 pm   #265
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Default Re: I found it! A very sorry looking MK14.

Quote:
Originally Posted by Buzby123 View Post
And there's more !

Today I found in the attic a box with about 30 databooks that I've not seen for years. One of them I think is the same NatSemi Memory Data as linked to a couple of posts ago.

I just had a quick look in it, and page 11-82 looks very interesting.

We MK14 owners know two things. (1) SoC cut every corner possible, (2) the PROMs get @***ing HOT !.

It looks like NatSemi had this heating in mind, and suggested a way to reduce it dramatically. That's what's on page 11-82.

Have any of you seen these PROMs in commercial products, did they get this hot in those applications ?

That's interesting App Note info info, I'd not noticed before - Especially as it was missing from the very abridged 20pgs pdf I'd previously got with the TTL/Bipolar PROM's programming procedure page and just the contents pages (minus the last one, listing the App Notes), and the cross-reference pages.

This 1977 databook 74S571 datasheet on pgs 5-13 to 5-17 also covers the 74S570 Open-Collector version, - as well as seemingly duplicating the Programming procedure for these on page 5-1.
It seems the 4 pages (3-16 to 3-19) later date unknown? one, I'd previously linked to was complete, but that NS had removed the programming procedure duplication from it (so needed other pages from their memory databook), as well as removing details on the internal circuitry - but they had added an extra SM PLCC version, and also that Testability note you'd noticed. So useful to have a copy of both versions.

To be fair to SoC, I don't think it was they who'd cut corners regarding power consumption reduction, as I'd never seen anyone else doing that, but National Semiconductor themselves - As most memory devices have a Chip Select as well as an Output Enable, to save unnecessary power.
If a program was running entirely from RAM, then you could save quite a bit, but if the with the monitor in the PROM's running to update display & scan keys etc. then the PROM's would still be frequently accessed - albeit needing to be selected for rather less than 50% of the time.


But rather than trying to mod the original design to include power-saving, then adding heatsink(s) would probably be simplest to preserve the PROM's a bit, and efficiency is not too important if not left running all day. If D/S thermally-conductive adhesive tape was used, rather than thermally-conductive epoxy etc, then they could be later removed for originality.

Or a metal plate clamped over the PROM etc. IC's, with some thermally-conductive gap-filler silicone rubber sheet underneath (would be easier if they'd laid the board out with PROM's adjacent to each other like others did!) - Just need to make up a suitable non-conductive clamp system, to fit around PCB, without some convenient mounting holes for it.

This does allow you to revert it be just a museum piece / retain resale value, whilst actually being able to use it wit less worries of these IC's failing - Although I'm tempted to just substitute a plug-in EPROM adaptor assembly for the PROM's, and keep the originals safe.

It may also be worth seeing if the bit lower power AMD 27S13A or N82S131 that SiriusHardware has tried could be obtained at a fair price, and are easily-programmable by most 74S571 programmers / supported by some common universal ones.
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Old 27th Mar 2021, 3:22 pm   #266
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Default Re: I found it! A very sorry looking MK14.

For absolute originality I suggest an original machine really does have to have 2 * DM74S571 fitted or at least available to be fitted because SOC never, to my knowledge, supplied alternatives. It wouldn't be a bad idea to have a pair of the cooler running types in whenever the machine is allowed off the leash, but if it ever comes to the day when the machine has to be sold on or given to a museum, there should really be a pair of DMs waiting to be put in it.

My MK14 was heavily used for several years and for most of that time it had the SOC supplied New-OS DM74S571s that it still has now, so although they do run very hot, somehow, generally, they keep working (...usually. One of Buzby's original SOC supplied PROMs failed after maybe 12-15 hours of use after decades of inactivity).

Mark's issue VI has N82S131Ns in it, I would be interested to know if they appear to him to run any cooler than the DM74S571s in his original issue IV. They still run quite warm, but to my mind not as hot as the DMs.
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Old 27th Mar 2021, 3:27 pm   #267
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Default Re: I found it! A very sorry looking MK14.

Micky is not having anymore experiments done on him, he has earned a decent retirement.

Vicky however is going to take his place, and the power reduction mod looks like it's the first to be tried.

Below is the /OE signal on the 571s while scanning keyboard and display. As you can see, it spends the vast majority of it's time in the dis-enabled state. The /OE pulses are 500nS wide, and the gaps are mostly 3uS to 15uS, so a power reduction of 90% is likely.

I'll try this mod next week, in a new thread.

Cheers,

Buzby
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Old 27th Mar 2021, 4:28 pm   #268
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Default Re: I found it! A very sorry looking MK14.

Quote:
Originally Posted by SiriusHardware View Post
Once the SC/MP is running under your program's control it is obviously up to you which row / column nodes you choose to scan and how you choose to respond to them, but I don't think any wiring convention ever got as far as being on paper.

It was arguably the next thing in the pipeline, SOC hinted at their future plans in one or more newsletters which I am sure Tim can effortlessly produce a link to, but instead they made the ZX80, which begat the ZX81 and eventually the Spectrum, so it was probably just as well that they decided to leave the MK14 where it was.

For that reason, I don't think there was ever a 'standard' way of connecting a QWERTY keyboard but that leaves us free to invent one, perhaps utilising an existing standard keyboard such as the ZX81 membrane keyboard, still widely available.

A QWERTY keyboard would only really make good sense with an alphanumeric display permanently fitted, ie, VDU or OrtonView, along with an alternative OS to support them. So once again, we are really veering towards the evolution of the MK14 into a NIBL machine or something like it.
I agree - it is something I plan to do to go with the machine when it has a VDU

The effortless link is:

http://www.computinghistory.org.uk/d...Update-Letter/

which talks about the BASIC board that needs a VDU and the 40Key (4x10 matrix) keyboard.

That matrix will mean that the ZX81 and Spectrum ones cannot be used as they are 5x8 but, I assume it would be logical to use a similar physical layout. We really need to try and contact Nick Toop and see what they actually planned in the way of a keyboard.

Out of interest the May 1980 Computing Today contains a Classified ad for an improved monitor with and Alphanumeric keyboard... so at least one was done by a third party.
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Old 27th Mar 2021, 4:33 pm   #269
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Default Re: I found it! A very sorry looking MK14.

Quote:
Originally Posted by Buzby123 View Post
Micky is not having anymore experiments done on him, he has earned a decent retirement.

Vicky however is going to take his place, and the power reduction mod looks like it's the first to be tried.

Below is the /OE signal on the 571s while scanning keyboard and display. As you can see, it spends the vast majority of it's time in the dis-enabled state. The /OE pulses are 500nS wide, and the gaps are mostly 3uS to 15uS, so a power reduction of 90% is likely.

I'll try this mod next week, in a new thread.

Cheers,

Buzby
Sounds interesting - nice find.
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Old 27th Mar 2021, 5:40 pm   #270
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Default Re: I found it! A very sorry looking MK14.

Quote:
a power reduction of 90% is likely.
Certainly an interesting lead, potentially interesting not only to lower the running temperature of the PROMs but also to take some of the heat off the regulator which, if mounted on board as it is supposed to be, rarely has a big enough heatsink.
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Old 27th Mar 2021, 6:02 pm   #271
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Default Re: I found it! A very sorry looking MK14.

I have a suspicion that the Tesla MH74S571 dissipates less heat, as I don't recall noticing them getting hot on my original prototype. My new r1.2 prototype has DM74S571's (Kindly donated by a very nice man) and I'm thinking of designing a grill attachment for them!
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Old 27th Mar 2021, 6:08 pm   #272
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Default Re: I found it! A very sorry looking MK14.

A couple of things I notice about the document in Tim's link in #268, one is the claim that the VDU is 'full ASCII' which is a bit disingenuous when the reality is upper case only and 64 characters altogether.

Another is the reference to 'adjustment' of issue I, II and IV PCBs to make way for the projected 2K memory expansion (meaning, presumably, removal of the unwanted PROM images on those versions). It's interesting that issue 1 (which I have never yet seen) is mentioned but issue 3 (which I thought I actually had seen) is not.
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Old 27th Mar 2021, 6:21 pm   #273
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Default Re: I found it! A very sorry looking MK14.

Code with a side order of eggy toast: What could be nicer?

The Tesla devices may not have appeared until quite a bit later and I think the AMD 27S... devices are also next-gen - those databooks linked to a few posts back have cross references to quite a few other-manufacturer devices that the Nat Semi devices are equivalents of but both the Tesla and AMD devices are absent from those tables.

I wonder if the Tesla clones came about as a result of a cold-war embargo which prevented US technology from being supplied to iron-curtain countries (pure speculation on my part, but it would explain why so few 'western' programmers support the Tesla devices, which maybe didn't appear on the world market until after the fall of the iron curtain).

The AMD 27S13As I got from kan_turk, being the 'A' version, are the faster version which usually goes hand in hand with being more power hungry, so the 'plain' 27S13 may be even more economical in that respect.
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Old 27th Mar 2021, 7:04 pm   #274
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Default Re: I found it! A very sorry looking MK14.

It seems the programming of the Tesla ones is closer to the Texas Instrument versions. So maybe they were a clone of those (that do seem less common that NS ones), and they have similar power consumption.
It's a pity there never seems to have been an 'L' Low power version, like with some EPROM's etc, before (High-Speed) CMOS versions were available.

It seems there was quite a lot of cloning of Western technology in the Eastern-bloc - Often whole Sinclair computers, including their own ULA.
And apparently they had a series of logic IC's in DIL packages with a metric pitch! (Recently found RS sell 2.5mm pitch veroboard, after someone bought it by mistake, when there's very few metric-pitch leaded connectors etc.)
The only Russian etc. made semiconductors that seem to make it over here back then, were transistors in those 5" B&W Rigonda VL100M TV's, popular with Caravaners etc. as had a bolt on the back PSU plugged into TV's 12V DC input.
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Old 27th Mar 2021, 7:15 pm   #275
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Default Re: I found it! A very sorry looking MK14.

Yes, it's been suggested before that the MH devices could actually be programmed using the hardware method and algorithm for the SN (Texas) prefix devices - only trouble is, Texas don't ever seem to have made an SN74S571 so it's not as though you can just choose 'Texas / SN74S571' on your 'western' programmer to programme MH74S571s.

Texas did make a SN74S287, and here is an article about programming those - the author points out what may be a critical difference between the SN and MH devices (roughly 8th paragraph down) so they may not be as directly programmer-compatible as it first seems.

http://randomvariations.com/2014/09/...87-programmer/
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Old 27th Mar 2021, 10:19 pm   #276
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Default Re: I found it! A very sorry looking MK14.

I hadn't seen that "Christopher" 2014 posting before.
In 2019 I showed that the Tesla PROMs (MH74-188, -S287, and -S571) had those similar part numbers and used exactly the same programming protocol as the earliest TI (SN74-) PROMs. But TI didn't have a '571.
The TI data shows the '287 programs 'the other way'. I'm not sure why "Christopher" believes the MH74S287 does not. He wasn't using them, just warning to check the datasheet.
Later TI PROMs have different prefixes and require other/more voltages in their programming sequence.
How far back do the Tesla chips date? Certainly to 1989.
Remember that rogue "MH74S571" page in German which confusingly indicated 21V?
It's actually a page of Fairchild 93438 from a databook published in DDR, 1989. The MH74S571 was described immediately before that (without programming details). And somebody didn't notice the change.
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Old 27th Mar 2021, 11:09 pm   #277
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Default Re: I found it! A very sorry looking MK14.

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I hadn't seen that "Christopher" 2014 posting before.
In 2019 I showed that the Tesla PROMs (MH74-188, -S287, and -S571) had those similar part numbers and used exactly the same programming protocol as the earliest TI (SN74-) PROMs. But TI didn't have a '571.
The TI data shows the '287 programs 'the other way'. I'm not sure why "Christopher" believes the MH74S287 does not. He wasn't using them, just warning to check the datasheet.
Later TI PROMs have different prefixes and require other/more voltages in their programming sequence.
How far back do the Tesla chips date? Certainly to 1989.
Remember that rogue "MH74S571" page in German which confusingly indicated 21V?
It's actually a page of Fairchild 93438 from a databook published in DDR, 1989. The MH74S571 was described immediately before that (without programming details). And somebody didn't notice the change.
A year ago I translated a data sheet from Czech from the Tesla manual that details the programming procedure in this thread: https://www.vintage-radio.net/forum/...d.php?t=146388 (first post) I have since received details from an actual Czech with experience of programming them that confirms my translation (transliteration?) was broadly correct, along with some designs that I am not at liberty to divulge but I can use to guide my own design.
AFAIK although there are similarities, Tesla 74S571 PROMs need specific programming that is different in the details. One of my many projects in my "in progress" list is a Arduino based programmer for Tesla MH74S571 PROMS.
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Old 27th Mar 2021, 11:12 pm   #278
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Default Re: I found it! A very sorry looking MK14.

Crumbs I just looked at the date, that was nearly 3 years ago!
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Old 27th Mar 2021, 11:16 pm   #279
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Default Re: I found it! A very sorry looking MK14.

Quote:
In 2019 I showed...
It was your work I was referring to in #275. If anyone has a Tesla MH74S287 and a programmer which can natively programme the SN74S287 then it would be great if they could try programming the MH74S287 'as though' it was an SN74S287.

Did you ever complete the conversion of the SOC PROM blower code to the MH... compatible version and compatible hardware which you were pursuing in this thread...?

https://www.vintage-radio.net/forum/...d.php?t=160247

I think you got as far as making a working conversion of the PROM editor code but we never did hear whether you also did that for the PROM blower code.
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Old 27th Mar 2021, 11:21 pm   #280
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that was nearly 3 years ago!
A sobering thought, we have now been going on about the MK14 and related matters for longer than the machine itself lasted as a commercial product.
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