Fitting a Minerva EEPROM to a Issue 5 QL

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Vyper68
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Fitting a Minerva EEPROM to a Issue 5 QL

Postby Vyper68 » Wed Mar 11, 2020 8:25 am

Hi
I have finally picked up a QL after thinking about it for a long time and the one I took a punt on turned out to be a working model ( after a fashion ). I need a new bubble mat as some keys stick down and also the CTRL key doesn't work. So I have ordered a new membrane from RWAP. So this is a Issue 5 PCB and the serial says it's a D11 build standard with JM Mask ROM's fitted.

I would like to fit a Minerva EEPROM to update it and right now I cannot afford to get a new Disk I/F with Minerva fitted and the Kempston I/F works pretty well. So I have a few Winbond 27c512 EEPROM's and have seen that it can be done but involves changing some Jumpers and/or fitting some wires so is there someone who can give me some help to make this happen?

I have read some threads on fitting 27c512's but I need a bit more information.


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martyn_hill
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Re: Fitting a Minerva EEPROM to a Issue 5 QL

Postby martyn_hill » Wed Mar 11, 2020 9:23 am

Hi Vyper68 :-)

You have a few options and the final approach would be determined by a few factors, namely:

a) Whether or not your Issue5 board has IC17 still fitted (later builds - I forget which build-standard - settled on ROMs and dispensed with IC17 - originally a quad 2 i/p NAND)
b) How much you want to modify your mainboard
c) Availability and confidence with a soldering iron and/or ability to prepare/etch a simple PCB.
d) Availability of a Minerva carrier-board from eBay or SMR (much preferred option.)

Option d) is at one end of the spectrum, in terms of ease of fitting and maintaining the mainboard as-is, but relies on availability of Minerva carrier-board.

At the other end, you have the approach that I took with one of my Iss5 boards that still had the IC17 (and the 'piggy-back-EPROM-with-flying-lead' arrangement.) Not recommended nor for the faint of heart, but very DIY-able with minimal specialist equipment...

In the middle, you have the option to prepare and etch your own EPROM carrier-board using the design files available or linked elsewhere on the forum.

All options assume that you have the equipment to erase and then reprogram a 512kb EPROM.

Before diving-in, which of the factors above are available or important to you?


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Re: Fitting a Minerva EEPROM to a Issue 5 QL

Postby Chr$ » Wed Mar 11, 2020 11:35 am

Have you seen these from Vitaliy in Russia?

https://www.sellmyretro.com/offer/detai ... ches-30375

I have them in my working QL's. Plug and play with no faff and really not that expensive. I don't have the adapter to program them and I needed one with a Finnish ROM, so just asked Vitaliy to supply one with Italian removed and the Finnish version in it's place.


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Re: Fitting a Minerva EEPROM to a Issue 5 QL

Postby Vyper68 » Wed Mar 11, 2020 11:46 am

Chr$ wrote:Have you seen these from Vitaliy in Russia?

https://www.sellmyretro.com/offer/detai ... ches-30375

I have them in my working QL's. Plug and play with no faff and really not that expensive. I don't have the adapter to program them and I needed one with a Finnish ROM, so just asked Vitaliy to supply one with Italian removed and the Finnish version in it's place.


Do these drop straight into an Issue 5 PCB without mods do you know?


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tofro
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Re: Fitting a Minerva EEPROM to a Issue 5 QL

Postby tofro » Wed Mar 11, 2020 11:52 am

Vyper68 wrote:
Do these drop straight into an Issue 5 PCB without mods do you know?


As long as you don't have the 3-chips version (that's a simple identification, two of the ROMs are stacked in the socket), it should plug right into an issue5.

Tobias


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Re: Fitting a Minerva EEPROM to a Issue 5 QL

Postby Vyper68 » Wed Mar 11, 2020 11:59 am

martyn_hill wrote:Hi Vyper68 :-)

You have a few options and the final approach would be determined by a few factors, namely:

a) Whether or not your Issue5 board has IC17 still fitted (later builds - I forget which build-standard - settled on ROMs and dispensed with IC17 - originally a quad 2 i/p NAND)
b) How much you want to modify your mainboard
c) Availability and confidence with a soldering iron and/or ability to prepare/etch a simple PCB.
d) Availability of a Minerva carrier-board from eBay or SMR (much preferred option.)

Option d) is at one end of the spectrum, in terms of ease of fitting and maintaining the mainboard as-is, but relies on availability of Minerva carrier-board.

At the other end, you have the approach that I took with one of my Iss5 boards that still had the IC17 (and the 'piggy-back-EPROM-with-flying-lead' arrangement.) Not recommended nor for the faint of heart, but very DIY-able with minimal specialist equipment...

In the middle, you have the option to prepare and etch your own EPROM carrier-board using the design files available or linked elsewhere on the forum.

All options assume that you have the equipment to erase and then reprogram a 512kb EPROM.

Before diving-in, which of the factors above are available or important to you?


Hi & Thanks for the reply,

My QL is a model that does not have IC17 fitted, just the two mask JM ROM's and some Zero Ohm resistors in the Jumper links and you are correct regards EEPROM/EPROM programming I have one to hand. I also have good experience with a soldering iron and working on old computers. My main hobby is repairing old 8-Bits for friends or to add to my collection and making the odd interface from existing Gerber files. I have no experience in making my own PCB's but maybe that is something I should have a look at. I have the time these days, either that or make something with Veroboard. I have no problem modifying the QL or should I say Tinkering? :)
My main objective was to upgrade the OS to a more modern version and Minerva seems to be one of the most popular ones that everyone uses. So I was wanting to change it before I start using the QL properly.


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Re: Fitting a Minerva EEPROM to a Issue 5 QL

Postby Pr0f » Wed Mar 11, 2020 1:13 pm

There was another thread on this recently.

From what I remember with an issue 5 board :

1) A15 on your Eprom is on pin 1 - but sinclair have tied that to pin 28 (5v) so you need to reroute the actual A15 signal which is on either the OE or CE pin of the ROM sockets (CE probably, as the 2 masked ROMS have opposite polarity pin selects and A15 is used to gate them.

2) OE is opposite polarity to what you want - as it's active high not active low which is what your eprom is looking for.

You could drive /OE and /CE together from an inverted copy of ROMOEH signal (you'll need to either bend the eprom pins out or use an adaptor), and pin 1 on the Eprom needs to see A15 signale currently languishing on what would be your /CE pin on the Eprom.


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Re: Fitting a Minerva EEPROM to a Issue 5 QL

Postby martyn_hill » Wed Mar 11, 2020 2:28 pm

Hi agan!

Being reminded of Vitaly's 'multi-ROM' availability, I'd recommend like Chr$ to go that route as the path of least resistance :-)

However, should you want to 'tinker', just let us know - several options, depending upon your taste...


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Re: Fitting a Minerva EEPROM to a Issue 5 QL

Postby Pr0f » Wed Mar 11, 2020 3:08 pm

martyn_hill wrote:Hi agan!

Being reminded of Vitaly's 'multi-ROM' availability, I'd recommend like Chr$ to go that route as the path of least resistance :-)

However, should you want to 'tinker', just let us know - several options, depending upon your taste...


+1 on that - you get to have 8 different ROMS available, at the flick of some dip switches, and can toggle your Toolkit 2 or other 16K top of the ROM area image on and off as well.

That way you can have JM / JS and several versions of Minerva, or even try Tyche - I would not recommend earlier ROM versions of the QL except out of curiosity - lot's of stuff broken there...


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Re: Fitting a Minerva EEPROM to a Issue 5 QL

Postby Derek_Stewart » Thu Mar 12, 2020 9:37 am

Hi,

I fitted on of these Teroid ROM Switchers to Issue 5,6,7 boards, all worked as expected.

The only thing I find limiting is if the ROM images in a certain location on the switcher unit needs changed, than the unit has to be put into an eprom programmer. It would be nice if the rom images could be software updated from the QL.

I remember in the 1990s some one in the Newcastle QL group had board in his QL, which he could change the ROM image with a manual read/write switch. Pity I did not get one.


Regards,

Derek

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