13 replies to this topic

[Wonder007]

I know masked roms are expensive and would only be used to mass produce games (most of the time). Are there any Atari 2600 protos that use masked roms? There is somebody trying to sell me a prototype and says that it is a masked rom....


What do you guys think????

[CPUWIZ]

Wonder007, on Wed Aug 16, 2006 9:41 PM, said:

I know masked roms are expensive and would only be used to mass produce games (most of the time). Are there any Atari 2600 protos that use masked roms? There is somebody trying to sell me a prototype and says that it is a masked rom....


What do you guys think????

A lot of the Activision protos are like that, it's not a proto per se', but a preview or review cart.

[Wonder007]

CPUWIZ, on Wed Aug 16, 2006 11:44 PM, said:

Wonder007, on Wed Aug 16, 2006 9:41 PM, said:

I know masked roms are expensive and would only be used to mass produce games (most of the time). Are there any Atari 2600 protos that use masked roms? There is somebody trying to sell me a prototype and says that it is a masked rom....


What do you guys think????

A lot of the Activision protos are like that, it's not a proto per se', but a preview or review cart.

Oh, but I WONDER why some companies like Activision would invest more money in using a masked rom as opposed to an EPROM??

[CPUWIZ]

They knew the game was finished and sent out "protos" of the cart (before the label, manual and box was done) to reviewers, no need to make an EPROM cart, when your mask ROM run is already done and the game is ready for manufacturing.

[Wonder007]

CPUWIZ, on Wed Aug 16, 2006 11:57 PM, said:

They knew the game was finished and sent out "protos" of the cart (before the label, manual and box was done) to reviewers, no need to make an EPROM cart, when your mask ROM run is already done and the game is ready for manufacturing.

Oh, fascinating!!!!

[supercat]

Wonder007, on Wed Aug 16, 2006 11:41 PM, said:

I know masked roms are expensive and would only be used to mass produce games (most of the time). Are there any Atari 2600 protos that use masked roms? There is somebody trying to sell me a prototype and says that it is a masked rom....

Out of curiosity, how often were OTPs used back then? Even in some third-party production games I've seen cerdip EPROMs; the cost of the silicon was sufficiently high compared with the cost of packaging that I don't think OTPs were as common then as today.

[Wonder007]

supercat, on Thu Aug 17, 2006 2:02 AM, said:

Wonder007, on Wed Aug 16, 2006 11:41 PM, said:

I know masked roms are expensive and would only be used to mass produce games (most of the time). Are there any Atari 2600 protos that use masked roms? There is somebody trying to sell me a prototype and says that it is a masked rom....

Out of curiosity, how often were OTPs used back then? Even in some third-party production games I've seen cerdip EPROMs; the cost of the silicon was sufficiently high compared with the cost of packaging that I don't think OTPs were as common then as today.

Good question supercat......btw, I don't want to sound dumb ...... what is a cerdip EPROM? what are OTP's?

[CPUWIZ]

supercat, on Thu Aug 17, 2006 12:02 AM, said:

Wonder007, on Wed Aug 16, 2006 11:41 PM, said:

I know masked roms are expensive and would only be used to mass produce games (most of the time). Are there any Atari 2600 protos that use masked roms? There is somebody trying to sell me a prototype and says that it is a masked rom....

Out of curiosity, how often were OTPs used back then? Even in some third-party production games I've seen cerdip EPROMs; the cost of the silicon was sufficiently high compared with the cost of packaging that I don't think OTPs were as common then as today.

About 90% of Froggo carts use a 2764 OTP. with only the bottom half utilized for their 4K games, the rest are the blob-style. I have also seen some Spectravision carts with OTP's.

[Wonder007]

This is a very interesting topic. I may sound dumb but I never knew there were variations with masked roms.

INTERESTING!!!

[CPUWIZ]

Wonder007, on Thu Aug 17, 2006 7:31 PM, said:

This is a very interesting topic. I may sound dumb but I never knew there were variations with masked roms.

INTERESTING!!!

There aren't, we were referring to PROM's.

EPROM = Erasable Programmable Read Only Memory
OTPROM = One Time Programmable Read Only Memory

[supercat]

Wonder007, on Thu Aug 17, 2006 7:41 AM, said:

Good question supercat......btw, I don't want to sound dumb ...... what is a cerdip EPROM? what are OTP's?

A cerdip EPROM is an embedded-charge programmable read only memory chip which is packaged in a ceramic dual-inline package with a quartz window on top. Information is written into the memory by depositing charges on the gates of the bits. Bits with charged gates read as "zero"; other bits read as "one". Although it's possible to electrically deposit charges on the gates, they cannot be removed in that way. On the other hand, exposing those gates to ultraviolet light will dislodge the charges, thus erasing the memory (turning all the bits to "1"'s).

An OTP ("one time programmable") is an inexpensive windowless opaque package (typically plastic) containing an embedded-charge programmable read only memory cihp, just like an EPROM. Although the silicon chip would be erasable if somehow exposed to ultraviolet light, there's no quartz window and no way to shine ultraviolet light into the package. Thus, if a bit is programmed as a "zero", it is for all practical purposes stuck that way. Nowadays, OTP chips cost quite a bit less than EPROMs, but the relative price differential was not always so great. Given a choice between an $8 chip that can be erased if the contents become unwanted versus a $7 chip that can't, one might decide to spend the extra dollar as insurance. Even if there's only a 10% chance that it will be necessary to reburn a chip, that extra dollar may be worth it.

If, however, the choice is between a $1 chip and a $2 chip, there's no longer as much reason to use the EPROM. Even if you're looking at burning 100 chips that have a 50% chance of needing to be redone, one would be better off buying 200 OTP chips than buying 100 EPROMs. If the code doesn't work the first time, you'd spend $200 for EPROMs plus the labor of erasing all of them, versus spending $200 for OTPs with no labor required to ready the second set for programming. And if the code does work the first time, your $200 has bought you 100 spare OTPs.

[Wonder007]

Hey supercat...thanks for the information. That is very interesting information. I never knew there was so much to learn with eprom chips and masked roms. Thanks again- Wonder007

[Wonder007]

Hey supercat...thanks for the information. That is very interesting information. I never knew there was so much to learn with eprom chips and masked roms. Thanks again- Wonder007

[Bruce Tomlin]

I think OTP plastic EPROMs were just coming into fashion around 1982 or so. They are cheaper than ceramic windowed EPROMs, and more expensive than a large production run of mask ROM, but you can burn only as many as you need without a commitment to a Q10K production run.

They would have made plastic windowed EPROMs, but it wasn't possible to get the necessary hermetic seal between plastic and quartz.