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Last night I opened up one of my SMS1s (3010-A) to determine what kind of VDP it had (315-5124). To my surprise IC6 and IC7, which is where the 16KB of video RAM are normally socketed, had some unusual chips. IC6 was a SEGA 315-5330. IC7 was another chip, half as wide, and was different from the normal NEC RAM chips used. I don't remember the markings other than "JAPAN 8809".

My question is, does anyone know anything about the 315-5330? It appears to be some kind of memory controller (based on the fact that it's in socket IC6).

--
Eric Quinn

Quote

> Last night I opened up one of my SMS1s (3010-A) to determine what kind of VDP it had (315-5124). To my surprise IC6 and IC7, which is where the 16KB of video RAM are normally socketed, had some unusual chips. IC6 was a SEGA 315-5330. IC7 was another chip, half as wide, and was different from the normal NEC RAM chips used. I don't remember the markings other than "JAPAN 8809".

> My question is, does anyone know anything about the 315-5330? It appears to be some kind of memory controller (based on the fact that it's in socket IC6).

Not exactly, according to a list I have the 315-5330 is used in the 4 and 8 cartridge versions of the Mega Play arcade board, which is a Genesis connected to a subset of the SMS hardware which manages menus and game selection. (having it's own SMS VDP to drive a seperate monitor)

I think this system had one RAM chip for the VDP instead of two - perhaps the 3150-5330 takes care of interfacing them. I will try to confirm this if I can find my old Mega Play notes.

It's a shame the RAM doesn't have any other markings, otherwise I could try to find a datasheet to get an idea of the capacity.

Does it look like the board originally supported 2 RAMs and it was then modified to include the two new chips, or is the board layout different from the normal SMS?

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Quote

> It's a shame the RAM doesn't have any other markings,
> otherwise I could try to find a datasheet to get an idea of
> the capacity.

It does have more info, I just don't remember it now (I'm at work). I'll check it tonight.

Quote

> Does it look like the board originally supported 2 RAMs and it
> was then modified to include the two new chips, or is the
> board layout different from the normal SMS?

The layout is roughly the same as my other SMS1, but I believe the 315-5330 has more pins than the normal NEC RAM that went in that socket (IC6). Socket IC7 is also unusual: It has three rows for pins. Obviously, socket IC7 is intended to support chips of two different widths. My other SMS1 has a NEC RAM in that socket which is "full-width" (like a normal ROM chip). The SMS1 with the 315-5330 has a "halfwidth" chip (like a 7400 series chip).

I'll check pin-counts tonight and provide more information about the chip markings tomorrow.

--
Eric Quinn

I have more information about the system that includes the 315-5330. I've placed a scan (sorry the scan is a little dark, I don't have a digital camera) of the board at:

http://home.att.net/~e-quinn/sms.jpg

I've also listed the chip numbers in 5 SMS1 systems (3 of which are mine) at:

http://home.att.net/~e-quinn/pcb_chip.txt

The last entry is for the board scan linked to above.

Looking closely at the top left of the scan, you'll notice that IC7 is 28-pin and half-width . Also notice that the board can handle a full-width 28-pin ROM in IC7. Other SMS1 boards I have contain two full-width 28-pin NEC RAM chips. They do not have the capability of containing a half-width part. Furthermore, IC6 is 42 pins on this board, whereas on most boards it is 28 pins. Obviously, this is a new revision of the board designed to support a different VPD memory implementation.

--
Eric Quinn

Quote

> I've also listed the chip numbers in 5 SMS1 systems (3 of which are mine)

The HM65256BLSP-10 is a 32Kx8 SRAM chip made by Hitachi. Weird that it would be used for the VDP. I have the datasheet (including pin assignments) of it at my website in the System 24 arcade section, if you ever wanted to see if the high order address line was used for anything. (though I'd bet the latter 16K is simply unused)

Nice scan, the board does look a bit different from some pictures of a regular SMS that I have seen.

Quote

> Looking closely at the top left of the scan, you'll notice that IC7 is 28-pin and half-width . Also notice that the board can handle a full-width 28-pin ROM in IC7. Other SMS1 boards I have contain two full-width 28-pin NEC RAM chips. They do not have the capability of containing a half-width part. Furthermore, IC6 is 42 pins on this board, whereas on most boards it is 28 pins. Obviously, this is a new revision of the board designed to support a different VPD memory implementation.

I wonder what kind of memory arrangement the SMS models with the 'SMS2' VDP have, I'd assume those were the latest versions of hardware.

BTW, I couldn't make out where the missing IC8 location was on the SMS board, is it big enough to hold anything interesting?

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Quote

> BTW, I couldn't make out where the missing IC8 location was on
> the SMS board, is it big enough to hold anything interesting?

There's nothing on the board, that I can find, marked IC8 at all. The socket itself is missing. They skipped from IC7 to IC9. I can only speculate that the reason the IC8 socket is missing is due to historical reasons. As the board moved from prototype to production, the need for IC8 was dropped. Or, perhaps IC8 was intended for a separate PSG (before production 315-5214's were available with integrated PSG) or FM unit.

I'll update my doc to be more clear about IC8.

--
Eric Quinn

Author	Message
Eric R. Quinn Joined: 18 Sep 1999 Posts: 498 Location: Portland, Oregon USA	315-5330 Posted: Thu Feb 07, 2002 4:59 pm
	Last night I opened up one of my SMS1s (3010-A) to determine what kind of VDP it had (315-5124). To my surprise IC6 and IC7, which is where the 16KB of video RAM are normally socketed, had some unusual chips. IC6 was a SEGA 315-5330. IC7 was another chip, half as wide, and was different from the normal NEC RAM chips used. I don't remember the markings other than "JAPAN 8809". My question is, does anyone know anything about the 315-5330? It appears to be some kind of memory controller (based on the fact that it's in socket IC6). -- Eric Quinn

Charles MacDonald Joined: 28 Sep 1999 Posts: 1197	Posted: Thu Feb 07, 2002 5:44 pm
Charles MacDonald Joined: 28 Sep 1999 Posts: 1197	Quote > Last night I opened up one of my SMS1s (3010-A) to determine what kind of VDP it had (315-5124). To my surprise IC6 and IC7, which is where the 16KB of video RAM are normally socketed, had some unusual chips. IC6 was a SEGA 315-5330. IC7 was another chip, half as wide, and was different from the normal NEC RAM chips used. I don't remember the markings other than "JAPAN 8809". > My question is, does anyone know anything about the 315-5330? It appears to be some kind of memory controller (based on the fact that it's in socket IC6). Not exactly, according to a list I have the 315-5330 is used in the 4 and 8 cartridge versions of the Mega Play arcade board, which is a Genesis connected to a subset of the SMS hardware which manages menus and game selection. (having it's own SMS VDP to drive a seperate monitor) I think this system had one RAM chip for the VDP instead of two - perhaps the 3150-5330 takes care of interfacing them. I will try to confirm this if I can find my old Mega Play notes. It's a shame the RAM doesn't have any other markings, otherwise I could try to find a datasheet to get an idea of the capacity. Does it look like the board originally supported 2 RAMs and it was then modified to include the two new chips, or is the board layout different from the normal SMS? My Homepage

Eric R. Quinn Joined: 18 Sep 1999 Posts: 498 Location: Portland, Oregon USA	Posted: Thu Feb 07, 2002 6:21 pm
	Quote > It's a shame the RAM doesn't have any other markings, > otherwise I could try to find a datasheet to get an idea of > the capacity. It does have more info, I just don't remember it now (I'm at work). I'll check it tonight. Quote > Does it look like the board originally supported 2 RAMs and it > was then modified to include the two new chips, or is the > board layout different from the normal SMS? The layout is roughly the same as my other SMS1, but I believe the 315-5330 has more pins than the normal NEC RAM that went in that socket (IC6). Socket IC7 is also unusual: It has three rows for pins. Obviously, socket IC7 is intended to support chips of two different widths. My other SMS1 has a NEC RAM in that socket which is "full-width" (like a normal ROM chip). The SMS1 with the 315-5330 has a "halfwidth" chip (like a 7400 series chip). I'll check pin-counts tonight and provide more information about the chip markings tomorrow. -- Eric Quinn

Eric R. Quinn Joined: 18 Sep 1999 Posts: 498 Location: Portland, Oregon USA	More Information Posted: Fri Feb 08, 2002 4:20 pm
	I have more information about the system that includes the 315-5330. I've placed a scan (sorry the scan is a little dark, I don't have a digital camera) of the board at: http://home.att.net/~e-quinn/sms.jpg I've also listed the chip numbers in 5 SMS1 systems (3 of which are mine) at: http://home.att.net/~e-quinn/pcb_chip.txt The last entry is for the board scan linked to above. Looking closely at the top left of the scan, you'll notice that IC7 is 28-pin and half-width . Also notice that the board can handle a full-width 28-pin ROM in IC7. Other SMS1 boards I have contain two full-width 28-pin NEC RAM chips. They do not have the capability of containing a half-width part. Furthermore, IC6 is 42 pins on this board, whereas on most boards it is 28 pins. Obviously, this is a new revision of the board designed to support a different VPD memory implementation. -- Eric Quinn

Charles MacDonald Joined: 28 Sep 1999 Posts: 1197	Re: More Information Posted: Fri Feb 08, 2002 6:37 pm
Charles MacDonald Joined: 28 Sep 1999 Posts: 1197	Quote > I've also listed the chip numbers in 5 SMS1 systems (3 of which are mine) The HM65256BLSP-10 is a 32Kx8 SRAM chip made by Hitachi. Weird that it would be used for the VDP. I have the datasheet (including pin assignments) of it at my website in the System 24 arcade section, if you ever wanted to see if the high order address line was used for anything. (though I'd bet the latter 16K is simply unused) Nice scan, the board does look a bit different from some pictures of a regular SMS that I have seen. Quote > Looking closely at the top left of the scan, you'll notice that IC7 is 28-pin and half-width . Also notice that the board can handle a full-width 28-pin ROM in IC7. Other SMS1 boards I have contain two full-width 28-pin NEC RAM chips. They do not have the capability of containing a half-width part. Furthermore, IC6 is 42 pins on this board, whereas on most boards it is 28 pins. Obviously, this is a new revision of the board designed to support a different VPD memory implementation. I wonder what kind of memory arrangement the SMS models with the 'SMS2' VDP have, I'd assume those were the latest versions of hardware. BTW, I couldn't make out where the missing IC8 location was on the SMS board, is it big enough to hold anything interesting? My Homepage

Eric R. Quinn Joined: 18 Sep 1999 Posts: 498 Location: Portland, Oregon USA	Re: More Information Posted: Fri Feb 08, 2002 7:00 pm
	Quote > BTW, I couldn't make out where the missing IC8 location was on > the SMS board, is it big enough to hold anything interesting? There's nothing on the board, that I can find, marked IC8 at all. The socket itself is missing. They skipped from IC7 to IC9. I can only speculate that the reason the IC8 socket is missing is due to historical reasons. As the board moved from prototype to production, the need for IC8 was dropped. Or, perhaps IC8 was intended for a separate PSG (before production 315-5214's were available with integrated PSG) or FM unit. I'll update my doc to be more clear about IC8. -- Eric Quinn

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