JS ROM creation

[Paul]

Thanks! That´s interesting stuff to know.

Just wonder why Sinclair made it that complicated, having e.g. a ROM upgrade of a SAM Coupe in mind?

That's pretty easy to answer. As always with Sinclair: make it as cheap as possible

[1024MAK]

Well...

• if SuperBASIC and QDOS had been able to keep within the allocated 32k bytes
• and time had allowed for bug free fully functional code to be ready

Then all production QL's would have been supplied with one 32k byte mask ROM chip, or two 16k byte mast ROM chips (that is after all what the board was supposed to have), it would have been a lot simpler

Alternatively, if Sinclair had allowed for 128k bytes of ROM space, with 64k bytes allocated to SuperBASIC and QDOS (could have been in two 32k byte ROM chips), and 64k bytes allocated to the cartridge port (a much more realistic amount compared to the 16k bytes we ended up with, or the planed for 32k bytes)...

But then, these are retrospective thoughts...

As indicated above, Sinclair wanted the cost kept low, but with as much functionality as possible from the code in the ROM. But it did not fit...

Mark

[chriskgnr]

About the spreadsheet, what is the difference between the ' Chip ' and ' PCB ' colums? If i burn and use two 27(C)256, for the 0000 and 8000 parts of firmware, the same moding is needed?

[Derek_Stewart]

Hi,

Both sockets are electrical the same, so a single eprom large enough to take the rom image.

I would use Minerva, rather than JS. Because the graphics are faster, there is multi-tasking basic, most of the bugs in the rom have been removed, selectable second screen available on power up, Better 128K ram test.

[1024MAK]

About the spreadsheet, what is the difference between the ' Chip ' and ' PCB ' colums? If i burn and use two 27(C)256, for the 0000 and 8000 parts of firmware, the same moding is needed?

The chip column electrically is the same as the PCB column. The reason for the two columns is the signal name. The PCB column tells you which 68008 or Sinclair named logic signal is present, while the Chip column tells you the name of the function as far as the chip is concerned.

Both sockets are the same unless the board has been modified.

When using EPROM's, the /OE inputs have to be driven via some extra logic because they are active low (the ROM chips use an active high signal) and some logic is needed to correctly select just one EPROM chip at a time. It may be easier to use a single 64k byte EPROM 27C512 chip.

I did work it out, but have misplaced the details

If you do want to use two EPROM chips and wire it like the picture I posted earlier in the thread, shout out and I will either work out the wiring, or post the rest of the photos (the QL in the photo is one of mine).

Mark

[chriskgnr]

I'll try to figure it out. If not i will shout out loud for your help!

[QLObi]

Hallo Stefan,
das ist im deutschen Forum aber auch schon veröffentlicht worden.

Detlef