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Hello,

Does someone who has access to the USA version of Great Ice Hockey could open it and take detailed photos of both side of the board?

I'd like to confirm the wiring and see if we can decide whether the ROM chip may house 64 KB or 128 KB of memory. The game useful contents is exactly 64 KB, when I dumped it the later region returned 0x00. It is difficult to say if those 0x00 stem from the board wiring/layout of if they are somehow stored in the ROM chip (because 128 KB are way more common).

Thanks!

Hope it will be usefull

SMS-GreatIceHockey-Board-2.jpg (2.56 MB)

SMS-GreatIceHockey-Board-1.jpg (2.44 MB)

Another board revision.

Dumped rom is full of 0x00 @ 0x10000 (until end ; 0x1FFFF)

IMG_20190402_100344.jpg (334.53 KB)

IMG_20190402_100359.jpg (253.66 KB)

Thank you both!

ichigobankai: you means it returns 0x00 untl 0x1FFFF ?
Does it start mirroring at some point, e.g. if you try to access 64 pages up to 1 MB ? or it keeps returning 0x00 ?

Haven't looked at the pinout in details. Most ROM chips are storing 0xFF on unused section but I don't know if that's an artefact of production of is often choosen at the Assembler level. Does anyone knows?

In addition, a prototype cart of Great Ice Hockey that I own sports a 64 KB EPROM chip also unusual.

(The question I am asking is I am tempted to think maybe the official dump should be trimmed to 64 KB.)

yes full of 0x00 from 0x10000 to 0x1FFFF, then back to 0 adr (if you try to read more datas, like 256KB)

0x00 is a "real value" (need to be written), as blank/empty or new rom/eprom are 0xFF ;)

Capture d’écran 2019-04-02 à 10.30.43.png (38 KB)

0x10000

Capture d’écran 2019-04-02 à 10.30.51.png (59.08 KB)

0x20000

I guess it was cheaper to fabricate on a larger chip (some later games had 256KB on a 512KB chip), even though it was an integrated mapper. Knowing this to be the case, it's quite arbitrary what to put in the upper region.

Some preservationists might say it's important to retain this, and even to distinguish dumps where the unused area differs.

Does the checksum include the blank area?

Maxim wrote

Does the checksum include the blank area?

The checksum is for 64 KB.

Wouldn't all-zero data have no effect on the checksum (even infinite zeros)?
At least for simple CRC, I don't know about more advanced/secure hashing methods.

CRC algorithms are designed to be sensitive to that but indeed the Sega checksum is just a sum so zeroes don't affect it.

Author	Message
Bock Site Admin Joined: 08 Jul 2001 Posts: 8651 Location: Paris, France	Great Ice Hockey (USA) board pictures? Posted: Mon Apr 01, 2019 5:44 pm
	Hello, Does someone who has access to the USA version of Great Ice Hockey could open it and take detailed photos of both side of the board? I'd like to confirm the wiring and see if we can decide whether the ROM chip may house 64 KB or 128 KB of memory. The game useful contents is exactly 64 KB, when I dumped it the later region returned 0x00. It is difficult to say if those 0x00 stem from the board wiring/layout of if they are somehow stored in the ROM chip (because 128 KB are way more common). Thanks!

balkry Joined: 22 Feb 2005 Posts: 173 Location: Caen, France	Great Ice Hockey Board Posted: Mon Apr 01, 2019 7:18 pm
	Hope it will be usefull SMS-GreatIceHockey-Board-2.jpg (2.56 MB) SMS-GreatIceHockey-Board-1.jpg (2.44 MB)

ichigobankai Joined: 04 Jul 2010 Posts: 542 Location: Angers, France	Posted: Tue Apr 02, 2019 8:10 am
	Another board revision. Dumped rom is full of 0x00 @ 0x10000 (until end ; 0x1FFFF) IMG_20190402_100344.jpg (334.53 KB) IMG_20190402_100359.jpg (253.66 KB)

Bock Site Admin Joined: 08 Jul 2001 Posts: 8651 Location: Paris, France	Posted: Tue Apr 02, 2019 8:23 am
	Thank you both! ichigobankai: you means it returns 0x00 untl 0x1FFFF ? Does it start mirroring at some point, e.g. if you try to access 64 pages up to 1 MB ? or it keeps returning 0x00 ? Haven't looked at the pinout in details. Most ROM chips are storing 0xFF on unused section but I don't know if that's an artefact of production of is often choosen at the Assembler level. Does anyone knows? In addition, a prototype cart of Great Ice Hockey that I own sports a 64 KB EPROM chip also unusual. (The question I am asking is I am tempted to think maybe the official dump should be trimmed to 64 KB.)

ichigobankai Joined: 04 Jul 2010 Posts: 542 Location: Angers, France	Posted: Tue Apr 02, 2019 8:32 am
	yes full of 0x00 from 0x10000 to 0x1FFFF, then back to 0 adr (if you try to read more datas, like 256KB) 0x00 is a "real value" (need to be written), as blank/empty or new rom/eprom are 0xFF ;) Capture d’écran 2019-04-02 à 10.30.43.png (38 KB) 0x10000 Capture d’écran 2019-04-02 à 10.30.51.png (59.08 KB) 0x20000

Maxim Site Admin Joined: 19 Oct 1999 Posts: 14744 Location: London	Posted: Tue Apr 02, 2019 9:11 am
	I guess it was cheaper to fabricate on a larger chip (some later games had 256KB on a 512KB chip), even though it was an integrated mapper. Knowing this to be the case, it's quite arbitrary what to put in the upper region. Some preservationists might say it's important to retain this, and even to distinguish dumps where the unused area differs. Does the checksum include the blank area?

Bock Site Admin Joined: 08 Jul 2001 Posts: 8651 Location: Paris, France	Posted: Tue Apr 02, 2019 10:00 am
	Maxim wrote Does the checksum include the blank area? The checksum is for 64 KB.

KingMike Joined: 14 Oct 2008 Posts: 511	Posted: Tue Apr 02, 2019 11:24 pm
KingMike Joined: 14 Oct 2008 Posts: 511	Wouldn't all-zero data have no effect on the checksum (even infinite zeros)? At least for simple CRC, I don't know about more advanced/secure hashing methods.

Maxim Site Admin Joined: 19 Oct 1999 Posts: 14744 Location: London	Posted: Wed Apr 03, 2019 7:52 am
	CRC algorithms are designed to be sensitive to that but indeed the Sega checksum is just a sum so zeroes don't affect it.

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