HVC-STROM

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BootGod
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HVC-STROM

Post by BootGod »

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This is the most overly complicated looking "NROM" board I have ever seen. Simple 16K PRG/8K CHR game with PRG split into 2 8K ROMs and a big cluster of transistors,resistors, and caps. Anyone have any ideas why this would have been made this way and what the purpose of all the extra parts is?
tepples
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Post by tepples »

Might the split PRG have had something to do with expensive 16 KiB mask ROMs in 1983?
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Bregalad
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Post by Bregalad »

I just guess all transistors & resistors does the decoding for both ROM chips using all discrete componants (combining PRG /CE wth A13 in some weird way).

Plus, like HVC-SROM already seems to does, mix the two enables /RD and /A13 of the CHR ROM into one single one (with a transistor-resistor-made OR gate), to have reducted all pin counts to 24 (all single enable mask ROMs I presume). You'd have to check the pinout to be sure.
Great Hierophant
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Post by Great Hierophant »

Is the checksum of the combined PRG ROMs the same as it is in every other known J and U Pinball cart?
BootGod
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Post by BootGod »

Yep it has the same combined checksum as the rest of them.

Cost might have been a factor, you would think using 2 ROMs instead of 1, plus that other stuff would have cost more in the end, but who knows. Family BASIC is the only other cart I've seen split such a small ROM apart like this.

Bregaled, you are probably right, I didn't even notice that they were 24-pin ROMs! :P
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Bregalad
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Post by Bregalad »

By the way, boot god, I know you already are working a lot on buying every FC game out there and all, but I'd really have you tracing pinouts on each Nintndo-made board, and post them on the wiki, or the database, or something.
Standard boards (such as SLROM, TLROM, SKROM, TKROM, etc...) all have known pinouts, but I just discovered recently that AOROM had an additional enable input, that was completely undoccumented before, and I tried to find the differences between AN1ROM and ANROM (wich were AN1ROM is standard pinout while ANROM is Nintendo pinout). There is A LOT of boards, such as SEROM, SBROM, SL1ROM, SH1ROM, TL1ROM, and even more SROM, RROM wich would be nice to known their pinouts, wich are really obscure.
BootGod
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Post by BootGod »

Don't worry, it will get done at some point :)
Great Hierophant
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Post by Great Hierophant »

I believe that this is important to ensure the functionality of the game itself. If a game is uses both a SLROM and an SL1ROM board, then we should ask has the game changed or the rom changed? If the game has not changed, judging by the CRC, that is one less board whose quirks we have to worry about. An emulator can simply add it to the list of supported boards without having to actually worry whether it uses some unknown functionality.
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Bregalad
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Post by Bregalad »

I never had any boards with the infamous "1ROM" termination aside of AN1ROM, wich is ANROM with only 64 KB of PRGROM. I belive SL1ROM is completely different, and that is identical with SLROM, and that CHR ROM has only one /CE input (no /OE), so an additional 74HC32 OR gate should OR A13 and CHR /RD together to feed the single-enable CHR ROM signal.

I don't have any SL1ROM to check this on, tough.
Great Hierophant
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Post by Great Hierophant »

Bregalad wrote:I never had any boards with the infamous "1ROM" termination aside of AN1ROM, wich is ANROM with only 64 KB of PRGROM. I belive SL1ROM is completely different, and that is identical with SLROM, and that CHR ROM has only one /CE input (no /OE), so an additional 74HC32 OR gate should OR A13 and CHR /RD together to feed the single-enable CHR ROM signal.

I don't have any SL1ROM to check this on, tough.
You are right, AN1ROM only supports 64K PRG ROM, which was surprising since every other A*ROM board supported at least 128KB. However, this board is only for R.C. Pro Am. I assume that the MMC1 revision came before the AN1ROM revision. I believe that kevtris said that about the SL1ROM vs. SLROM. However, since several games use the same code with both boards, the hardware differences aren't important.
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Bregalad
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Post by Bregalad »

Yes, AN1ROM is the same as ANROM, but only 64 KB, and yes, it's as far we known only used in *early* revisions of R.C. pro-am. Later revisions used MMC1 (at least in america). However, you never known when another totally unknown game or another revision will use the same board.
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krzysiobal
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Re: HVC-STROM

Post by krzysiobal »

Schematics:
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sch.png
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aquasnake
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Re: HVC-STROM

Post by aquasnake »

It seems that a line OR logic is implemented with emitter followers.
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