QL ROM switcher

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janbredenbeek
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Re: QL ROM switcher

Postby janbredenbeek » Mon Sep 25, 2017 11:28 pm

tofro wrote:My first QL (unfortunately also bought for the highest possible price in 1985) already had an MG ROM, which still is IMHO the most usable original QL ROM - When prices dropped to low bottom, I bought another one, just for spares. I still have both and never really needed to scavenge the latter, fortunately....

Only much later I obtained a JM version from the UK, which started to annoy me soon, so it was upgraded to JS and later to Minerva (Original ROMs are still somewhere in a drawer, never to be looked at since).

My first QL (bought before the price drop) was a D15 JS, and I got the impression that after the price drop many QLs sold in Holland were older JMs (never saw an official MG because the QLs sold here were plain UK ones apart from the PSU, which was modified for 220V with Euro plug). Which matches the story that Sinclair dropped the price because of huge piles of unsold stock.
I now have 4 QLs, two of them D15 JS and two D09 JM with a mixture of 220V and 240V PSUs...

Jan.


Nasta
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Re: QL ROM switcher

Postby Nasta » Tue Sep 26, 2017 12:49 am

tofro wrote:
Nasta wrote:Sadly, no...
On the QL the ROMOEH line that selects the ROM is only generated for read cycles, and writes are necessary for programming the Flash chip in-circuit.
Even worse, if a GC or SGC is used, the board does not even generate write cycles on the bus when addressing these addresses :(


I maybe mis-formed my question: Can the ROM be programmed in an external programmer (all address lines and control lines accessible from a header). I wasn't actually asking that much ;)

Tobias


Ah... in that case the answer is yes. That's what the extra 3+1 turned pins on the underside are for (great idea, BTW). I'm guessing there is a nice little adapter for the programmer involved, too, since the DIL version of the 29F040 is a 32-pin chip.


tetroid
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Re: QL ROM switcher

Postby tetroid » Tue Sep 26, 2017 3:39 pm

Nasta wrote:
tofro wrote:
Nasta wrote:Sadly, no...
On the QL the ROMOEH line that selects the ROM is only generated for read cycles, and writes are necessary for programming the Flash chip in-circuit.
Even worse, if a GC or SGC is used, the board does not even generate write cycles on the bus when addressing these addresses :(


I maybe mis-formed my question: Can the ROM be programmed in an external programmer (all address lines and control lines accessible from a header). I wasn't actually asking that much ;)

Tobias


Ah... in that case the answer is yes. That's what the extra 3+1 turned pins on the underside are for (great idea, BTW). I'm guessing there is a nice little adapter for the programmer involved, too, since the DIL version of the 29F040 is a 32-pin chip.


Yes, you are right.
Little adapter to DIP32 for EEPROM programmer.

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tetroid
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Re: QL ROM switcher

Postby tetroid » Tue Sep 26, 2017 3:45 pm

dilwyn wrote:This is a good idea for a project, tetroid.

I would suggest including these versions:
JM ( fairly common in UK, useful for testing software, fairly similar to AH)
JS (most common uk rom)
MG - some of the most widely used national variants such as French/German), note that MGUK is a private non Sinclair version and may need permission from John Alexander to be used)
A few versions of Minerva
Tyche rom (although i can't remember if it would fit in QL ROM space and how compatible with BBQL)


Thank yoy, Dilwyn and all.
I think we can find 8 most popular ROM images.
In addition we can make the special ROM set for special languages / countries.


Silvester
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Re: QL ROM switcher

Postby Silvester » Wed Sep 27, 2017 2:10 pm

Sorry to be a bit negative, but I don't get it. I see it of very limited use, it could easily be so much more.

What _would_ be useful would be able to switch between JS, Minerva, and still have 384K Flash left over for SMSQ/E. Removing board to reprogram?, a bit awkward for average user to update.

Both GC and SGC leave aperture of last 128 bytes in OS Rom for hardware control (mk2 Minerva I2C, etc). Instead of 7400 stuck underneath, perhaps something with a little more facility?


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Peter
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Re: QL ROM switcher

Postby Peter » Wed Sep 27, 2017 3:48 pm

Silvester wrote:Sorry to be a bit negative, but I don't get it. I see it of very limited use, it could easily be so much more.

As soon as someone actually creates a piece of QL hardware, ideas come up what else could "easily" have been added. :) Then why not "easily" design it youself? ;)

From QL-SD I remember well the massive signal quality problems we ran into, when using a modern PLD on the PCB in the ROM socket. Really, I can blame nobody who stays on the save side, with simple 74xx there.


tetroid
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Re: QL ROM switcher

Postby tetroid » Wed Oct 25, 2017 10:37 pm

One USA QLer ask me about ROM switcher.

"Do you know if the switcher ROM is compatible with the US version of the QL? For example, I've heard that the JS and Minerva ROMs are not compatible replacements for the JSU ROM."

I have not american QL and I can not check.
Does american QL hardware is different from european and Minerva ROM can not work with american QL ?


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tofro
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Re: QL ROM switcher

Postby tofro » Wed Oct 25, 2017 10:49 pm

On a Rest-of-world QL, a timer tick is 1/50s.

On a US QL, a timer tick is 1/60s.

Video standards are different and the screen resolution is slightly different.

I am not sure what exactly would be affected, as most timings in the QL are measured in tight CPU loops that should be the same, but would assume some of the above would make US hardware incompatible with anything but a JSU ROM, at least in the video output and at least in TV mode (A Minerva ROM, for example, would most probably assume that more pixels fit on the screen than actually do).

Tobias


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Re: QL ROM switcher

Postby tetroid » Thu Oct 26, 2017 9:52 am

tofro wrote:On a Rest-of-world QL, a timer tick is 1/50s.

On a US QL, a timer tick is 1/60s.

Video standards are different and the screen resolution is slightly different.

I am not sure what exactly would be affected, as most timings in the QL are measured in tight CPU loops that should be the same, but would assume some of the above would make US hardware incompatible with anything but a JSU ROM, at least in the video output and at least in TV mode (A Minerva ROM, for example, would most probably assume that more pixels fit on the screen than actually do).

Tobias


Thank you for info, Tobias.
May be anybody of US QL users will respond later.


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Re: QL ROM switcher

Postby RWAP » Thu Oct 26, 2017 11:39 am

I have had a US QL in the past - the ROM switcher will work with it - the problem is the ROM version if you are going to use the QL with an American TV via the aerial socket, you need to use the JSU (american) ROM because of the difference in scan lines and the changes made to the character font to get around this.

Oddly, so far as I know, only War In the East and D-Day contain specific UDG fonts for use on American QLs !!

The US QLs I have seen also all have a small switch underneath the TV modulator, so that you can switch between UK and US output.



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