What are this Blank Sockets for?

mjelic · 10-05-2022, 08:37 PM

(07-05-2022, 01:02 AM)Ernest Wrote: by replacing ROM 1 with Microworld Basic V5.22 burnt into a 128K EPROM the board will boot up and behave as a standard 32K ROM Basic machine. Add into the ROM2 location, Wordbee or EDASM (or any of the ROMs designated for the C000h - DFFFh PAK location) and you can call this with the PAK command from basic, just as you would in a normal ROM base machine.

Now that IS, interesting... But I assume the standard Basic ROM has no understanding of how to work with floppies?

How about this: With one ROM and a switch (to flick one of the address lines high or low) would you be able to flick between a Standard 32K Basic, vs 128K Premium machine?

Ernest · 10-05-2022, 10:27 PM

You are correct, ROM BASIC knows nothing of disk drives, the floppy access routines are in the Boot ROM you are replacing.

However, I see no reason why you could not use a 256k ROM and bank switch between the Boot ROM bank and the ROM Basic bank selected by a switch.
Don't forget if you switch between banks with the power on the system will just hang, so a RESET will be required, best to just power down, switch and power back up.

Ernest

mjelic · 10-05-2022, 11:17 PM

Yep, agreed... Would never switch roms while machine is running. That's like doing a brain transplant with the patient still conscious. Smile

OK, so both the basic ROM and the Boot ROM are 128k jobs?? Holy mackerel that's a LOT of ROM to use up!! Aren't those things normally 8K or such?

I'm liking this bank switch idea, along with EDASM in there somewhere.

Ernest · 11-05-2022, 12:10 AM

(10-05-2022, 11:17 PM)mjelic Wrote: OK, so both the basic ROM and the Boot ROM are 128k jobs?? Holy mackerel that's a LOT of ROM to use up!! Aren't those things normally 8K or such?

I'm liking this bank switch idea, along with EDASM in there somewhere.

No they are not both 128k.

The Boot ROM is 64kbit or if you like 8KByte & Basic is normally 2x 64kbit or 2x 8KByte ROM's but can be burnt into one 128k (16KByte) to fit here.
So to make the bank switching work you would need to use a 256kbit (32KByte) ROM and switch between the upper and lower 128kbit (16KByte) halves with A14.
As the Boot ROM is only 64kbit (8KByte) you would leave the second half of the lower 128k empty then into the upper 128kbit (16KByte) you would place the two 64kbit (8KByte) ROM images into there.
Switching between Boot ROM and ROM Basic would be a case of changing pin 27 (A14) between a logic low and a logic High.

EDASM (if you like) will be in ROM2 position and would be ignored when booting with the normal Boot ROM. You may even be able to put TELCOM into ROM 3 but that is something I have not tried myself, as all my MB8342 Coreboards have my 512k MOD fitted, which encroaches over the ROM 3 location.

Ernest