Forums

hi guys this is the first time ive tryed to create a schematic so i dont know if i have it right is there anyone who can take a look at it and let me know what you think thats.

it is for a dual bios board for the master system which slots into place where the original bios would have been and lets you toggle between 2 bios chips which will be flashed M27C256B eeproms.

thanks

update:
files removed because updated.

RazorX wrote

hi guys this is the first time ive tryed to create a schematic so i dont know if i have it right is there anyone who can take a look at it and let me know what you think thats.

it is for a dual bios board for the master system which slots into place where the original bios would have been and lets you toggle between 2 bios chips which will be flashed M27C256B eeproms.

thanks

I'm not an expert but it seems good to me, All the pins should be common apart from the chip enable pin which is the selector.

You could go one step further and allow the circuit to select between 4 different BIOS's in one EPROM, 4 8kb chunks.

A13 Ground 1st 8kb
A14 Ground

A13 Ground 2nd 8kb
A14 +5v

A13 +5v 3rd 8kb
A14 Ground

A13 +5v 4th 8kb
A14 +5v

That way you can have the Prototype BIOS, 1.3, 2.0,.2.1

Thanks once I have this schematic right and can order 1 or 2 for testing I will see about doing that.

I'm just new to schematics so I don't know what size the holes should be for stuff or if the holes are already added as part of the eeprom section and where I added the through hole bit ect.

Is there some sort of app that will create a basic 3d render from the schematic?

ive updated schematic and board, i think it should work now but if anyone who knows about schematics could take a look and see if its correct thanks

update:
here is a 3d render of rev1 of the board.

update 2:
files removed because updated.

was having issues with the schematic so i changed a bit of it and better layed out the board so its smaller, i just need someone who can look over it for me and tell me what spacing i need between the holes for it too slot into a ic socket soldered to the master system motherboard and what size holes for the ic socket i need thanks.

here is the new improved 3d render and board.

update:
files removed because updated.

I've ordered what will hopefully be the final version of this board, once it is installed and tested I will post pictures and info for it.

Do it the easy way and use a 16KB EPROM or even a bigger (cheaper, easier to source and still pin compatible) EPROM chip.

Use the address lines to bank which "chip" you want to use. Cheaper and easier. If it's just two BIOSes you only need one wire (one address line) to select them.

On my system, I took a 128KB flash and partitioned it in two 32KB windows and left the rest unused. On the first partition I have SMS BIOS 1.3 and on the other partition I have the Japanese SMS BIOS. When I switch the region to Japan it boots with the Japanese BIOS.

i mainly wanted to do it for fun and to make it easier to replace either bios in the future also one of the bioses im using is an original alex the kidd bios so thats why i wanted to go down this route

RazorX wrote

i mainly wanted to do it for fun and to make it easier to replace either bios in the future also one of the bioses im using is an original alex the kidd bios so thats why i wanted to go down this route

Oh I see.

Well, on a sidenote, to make a BIOS with mapper work from EPROM, it's more involved work, though. Many years ago I did it on one SMS and it took like five logic chips to mimic the basic operation of the 315-5208 mapper chip. Too many wires, too.

my rev3 boards finally arrived so i have took some pics with my phone to show you guys what it looks like im pretty happy with the overall scale and look of it.

i just need to remove my old board and test this one but i dont think i will have any issues but i will let you know.

Author	Message
RazorX Joined: 27 Jul 2015 Posts: 11 Location: United Kingdom	SMS Dual Bios Schematic Posted: Mon Jul 27, 2015 8:47 pm Last edited by RazorX on Thu Jul 30, 2015 5:06 pm; edited 3 times in total
	hi guys this is the first time ive tryed to create a schematic so i dont know if i have it right is there anyone who can take a look at it and let me know what you think thats. it is for a dual bios board for the master system which slots into place where the original bios would have been and lets you toggle between 2 bios chips which will be flashed M27C256B eeproms. thanks update: files removed because updated.

Whitesnake Joined: 22 Dec 2004 Posts: 43 Location: UK	Posted: Tue Jul 28, 2015 11:39 am
Whitesnake Joined: 22 Dec 2004 Posts: 43 Location: UK	RazorX wrote hi guys this is the first time ive tryed to create a schematic so i dont know if i have it right is there anyone who can take a look at it and let me know what you think thats. it is for a dual bios board for the master system which slots into place where the original bios would have been and lets you toggle between 2 bios chips which will be flashed M27C256B eeproms. thanks I'm not an expert but it seems good to me, All the pins should be common apart from the chip enable pin which is the selector. You could go one step further and allow the circuit to select between 4 different BIOS's in one EPROM, 4 8kb chunks. A13 Ground 1st 8kb A14 Ground A13 Ground 2nd 8kb A14 +5v A13 +5v 3rd 8kb A14 Ground A13 +5v 4th 8kb A14 +5v That way you can have the Prototype BIOS, 1.3, 2.0,.2.1

RazorX Joined: 27 Jul 2015 Posts: 11 Location: United Kingdom	Posted: Tue Jul 28, 2015 11:45 am
	Thanks once I have this schematic right and can order 1 or 2 for testing I will see about doing that. I'm just new to schematics so I don't know what size the holes should be for stuff or if the holes are already added as part of the eeprom section and where I added the through hole bit ect. Is there some sort of app that will create a basic 3d render from the schematic?

RazorX Joined: 27 Jul 2015 Posts: 11 Location: United Kingdom	Posted: Tue Jul 28, 2015 3:39 pm Last edited by RazorX on Thu Jul 30, 2015 1:11 am; edited 1 time in total
	ive updated schematic and board, i think it should work now but if anyone who knows about schematics could take a look and see if its correct thanks update: here is a 3d render of rev1 of the board. update 2: files removed because updated.

RazorX Joined: 27 Jul 2015 Posts: 11 Location: United Kingdom	Posted: Wed Jul 29, 2015 2:56 pm Last edited by RazorX on Thu Aug 06, 2015 5:15 pm; edited 4 times in total
	was having issues with the schematic so i changed a bit of it and better layed out the board so its smaller, i just need someone who can look over it for me and tell me what spacing i need between the holes for it too slot into a ic socket soldered to the master system motherboard and what size holes for the ic socket i need thanks. here is the new improved 3d render and board. update: files removed because updated.

RazorX Joined: 27 Jul 2015 Posts: 11 Location: United Kingdom	Posted: Mon Sep 28, 2015 8:39 am
	I've ordered what will hopefully be the final version of this board, once it is installed and tested I will post pictures and info for it.

l_oliveira Joined: 29 Jan 2014 Posts: 95 Location: Brasilia, Brazil	Posted: Mon Sep 28, 2015 7:31 pm
	Do it the easy way and use a 16KB EPROM or even a bigger (cheaper, easier to source and still pin compatible) EPROM chip. Use the address lines to bank which "chip" you want to use. Cheaper and easier. If it's just two BIOSes you only need one wire (one address line) to select them. On my system, I took a 128KB flash and partitioned it in two 32KB windows and left the rest unused. On the first partition I have SMS BIOS 1.3 and on the other partition I have the Japanese SMS BIOS. When I switch the region to Japan it boots with the Japanese BIOS.

RazorX Joined: 27 Jul 2015 Posts: 11 Location: United Kingdom	Posted: Mon Sep 28, 2015 7:39 pm
	i mainly wanted to do it for fun and to make it easier to replace either bios in the future also one of the bioses im using is an original alex the kidd bios so thats why i wanted to go down this route

l_oliveira Joined: 29 Jan 2014 Posts: 95 Location: Brasilia, Brazil	Posted: Mon Sep 28, 2015 7:44 pm
	RazorX wrote i mainly wanted to do it for fun and to make it easier to replace either bios in the future also one of the bioses im using is an original alex the kidd bios so thats why i wanted to go down this route Oh I see. Well, on a sidenote, to make a BIOS with mapper work from EPROM, it's more involved work, though. Many years ago I did it on one SMS and it took like five logic chips to mimic the basic operation of the 315-5208 mapper chip. Too many wires, too.

RazorX Joined: 27 Jul 2015 Posts: 11 Location: United Kingdom	Posted: Mon Oct 12, 2015 1:43 pm
	my rev3 boards finally arrived so i have took some pics with my phone to show you guys what it looks like im pretty happy with the overall scale and look of it. i just need to remove my old board and test this one but i dont think i will have any issues but i will let you know.

Forums

View topic - SMS Dual Bios Schematic