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Via the amount of RAM, one can easily detect if the machine is an SG-1000, SC-3000 or Mark III / SMS.
Is there a way to find out if the SG-1000 is a Mark II?

Philipp

PkK wrote

Via the amount of RAM, one can easily detect if the machine is an SG-1000, SC-3000 or Mark III / SMS.
Is there a way to find out if the SG-1000 is a Mark II?

You could try changing the VRAM size to 4K and waiting for the rest of the VRAM data to stop being refreshed and change to 00/FF/garbage value, on the assumption that the custom VDP the Mark II has doesn't implement the RAM size control (AFAIK no other Sega VDPs do, so we're assuming the Mark II's VDP also doesn't -- but that may not be true)

I think somebody said even the SG-1000 can have the Sega custom the Mark II has, so this isn't foolproof however.

Not to nitpick but it's just "SG-1000 II", not "Mark II".

According to
http://www.rfgeneration.com/PHP/gethwinfo.php?ID=J-143-H-00010-A
Some early SG-1000 II still used the TMS9918 instead of the Sega 315-5066.

Looks like deciding SG-1000 vs SG-1000 II will be hard or impossible.

Philipp

Likewise, SMS1 and SMS2 VDPs are found in opposite models. I guess it's a manufacturing thing, they didn't want to throw away good chips so it makes sense to have some overlap in production parameters. If the purpose of the detection is to match chip capabilities, then it doesn't matter - what you have is a chip detection routine. If you just want to correctly identify the shape of the plastic on the outside, it's rather tricky.

PkK wrote

According to
http://www.rfgeneration.com/PHP/gethwinfo.php?ID=J-143-H-00010-A
Some early SG-1000 II still used the TMS9918 instead of the Sega 315-5066.

That was actually me who wrote that, haha. But yes, some SG-1000 IIs (including mine) use a discrete TMS9918 and SN76489 instead of the 315-5066. Pretty frustrating when you're trying to look for one that you can RGB mod.

Maxim wrote

Likewise, SMS1 and SMS2 VDPs are found in opposite models. I guess it's a manufacturing thing, they didn't want to throw away good chips so it makes sense to have some overlap in production parameters. If the purpose of the detection is to match chip capabilities, then it doesn't matter - what you have is a chip detection routine. If you just want to correctly identify the shape of the plastic on the outside, it's rather tricky.

It is not just about the shape of plastic. SG-1000 and SG-1000 II differ in more than just graphics chips. There are differences in the controller port and cartridge port pinouts.

Philipp

Author	Message
PkK Joined: 07 Aug 2007 Posts: 220 Location: Yach, Germany	Detecting the Mark II Posted: Mon Feb 20, 2017 8:33 am
	Via the amount of RAM, one can easily detect if the machine is an SG-1000, SC-3000 or Mark III / SMS. Is there a way to find out if the SG-1000 is a Mark II? Philipp

Charles MacDonald Joined: 28 Sep 1999 Posts: 1197	Posted: Mon Feb 20, 2017 9:44 pm
Charles MacDonald Joined: 28 Sep 1999 Posts: 1197	PkK wrote Via the amount of RAM, one can easily detect if the machine is an SG-1000, SC-3000 or Mark III / SMS. Is there a way to find out if the SG-1000 is a Mark II? You could try changing the VRAM size to 4K and waiting for the rest of the VRAM data to stop being refreshed and change to 00/FF/garbage value, on the assumption that the custom VDP the Mark II has doesn't implement the RAM size control (AFAIK no other Sega VDPs do, so we're assuming the Mark II's VDP also doesn't -- but that may not be true) I think somebody said even the SG-1000 can have the Sega custom the Mark II has, so this isn't foolproof however.

ApolloBoy Joined: 30 Jan 2007 Posts: 314 Location: San Jose, CA	Posted: Tue Feb 21, 2017 5:59 pm
	Not to nitpick but it's just "SG-1000 II", not "Mark II".

PkK Joined: 07 Aug 2007 Posts: 220 Location: Yach, Germany	Posted: Wed Feb 22, 2017 12:00 pm
	According to http://www.rfgeneration.com/PHP/gethwinfo.php?ID=J-143-H-00010-A Some early SG-1000 II still used the TMS9918 instead of the Sega 315-5066. Looks like deciding SG-1000 vs SG-1000 II will be hard or impossible. Philipp

Maxim Site Admin Joined: 19 Oct 1999 Posts: 14741 Location: London	Posted: Wed Feb 22, 2017 8:22 pm
	Likewise, SMS1 and SMS2 VDPs are found in opposite models. I guess it's a manufacturing thing, they didn't want to throw away good chips so it makes sense to have some overlap in production parameters. If the purpose of the detection is to match chip capabilities, then it doesn't matter - what you have is a chip detection routine. If you just want to correctly identify the shape of the plastic on the outside, it's rather tricky.

ApolloBoy Joined: 30 Jan 2007 Posts: 314 Location: San Jose, CA	Posted: Sat Feb 25, 2017 6:31 pm
	PkK wrote According to http://www.rfgeneration.com/PHP/gethwinfo.php?ID=J-143-H-00010-A Some early SG-1000 II still used the TMS9918 instead of the Sega 315-5066. That was actually me who wrote that, haha. But yes, some SG-1000 IIs (including mine) use a discrete TMS9918 and SN76489 instead of the 315-5066. Pretty frustrating when you're trying to look for one that you can RGB mod.

PkK Joined: 07 Aug 2007 Posts: 220 Location: Yach, Germany	Posted: Mon Feb 27, 2017 11:26 am
	Maxim wrote Likewise, SMS1 and SMS2 VDPs are found in opposite models. I guess it's a manufacturing thing, they didn't want to throw away good chips so it makes sense to have some overlap in production parameters. If the purpose of the detection is to match chip capabilities, then it doesn't matter - what you have is a chip detection routine. If you just want to correctly identify the shape of the plastic on the outside, it's rather tricky. It is not just about the shape of plastic. SG-1000 and SG-1000 II differ in more than just graphics chips. There are differences in the controller port and cartridge port pinouts. Philipp

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