antiRepublicrat: Duh, that's the definition of a PROM.
Actually you are confused on two counts.
First I was replying to your statement:
antiRepublicrat: ...to be placed on a ROM (or EPROM, can't remember)
Second: EPROM's are PROM's
Actually, they reverse-engineered an entire published specification, of which the software was a part.
Not true. First, the IBM bios was proprietary - it was not a published specification. Second, the hardware was a published standard so reverse-engineering was not needed.
This all started because you wanted to make a mountain out of a molehill. You lost the main argument, so you started delving into semantics and definitions.
You made an incorrect statement when you claimed Compaq reverse-engineered that hardware and you have spent days unsuccessfully trying to spin it into truth - bringing use to the core nonsense statement of firmware<>software.
A mountain has been made, but is looks like you were the builder.
I know these days most BIOSes are on EEPROMS, I just couldn't remember whether what type of chip the original IBM PC BIOS was on. I don't remember anybody flashing a BIOS in the early days, so I guess either ROM or PROM.
Second: EPROM's are PROM's
Wrong again. You truly do not know this subject you accused me of not knowing. Remember that you're talking to somebody who used to program these.
PROMs (Programmable Read-Only Memory) are written by overloading fuses built into the chip. When shipped, all the fuses are intact, representing 1s. Selectively overloading the fuses will blow them, thus changing them to represent 0s. Thus in the end you have a bunch of 1s and 0s representing what you wanted to be in the chip. This is a one-time only process, as you can't un-blow the fuses.
EPROMs (Erasable Programmable Read-Only Memory) use floating gates and capacitors to hold charges even when no power is applied. When erased, each cell holds a charge, counting as a 1. Writing is accomplished by applying high voltage to the various gates, dissipating the charge, and a gate with no charge is read as a 0. The erasing is done by exposure to UV light, which re-charges all of the gates. This is why if you you've ever seen an old chip with a quartz window on the top, it was an EPROM, the window being there to expose the chip to UV light (and no, opening your case and leaving an EPROM exposed to office light for a few days isn't enough to erase one).
There is a slight exception, as some people have packaged EPROMS in windowless cases, making them effectively PROMS in function only, but not design. The reason for this is that PROMs are cheap, while EPROMS are expensive, but lots of people with EPROM burners didn't always need the chips to be reprogrammable. Enter a cheaper, windowless EPROM, cheaper than an EPROM (that quartz window isn't cheap), and definitely cheaper than buying a PROM burner in addition to your EPROM burner. These are called OTP (One Time Programmable) EPROMs. They are not PROMs because the underlying technology is different, and you could still pop open the case and erase the chip with UV.
So you can't play logic games later: PROM and EPROM technology are radically different. The set PROM is distinct from the set EPROM, with no overlap.
BTW, EEPROMs (Electrically Erasable Programmable Read-Only Memory) can be erased using electrical signals, and are what's normally used today for BIOSes. Acutally, BIOSes tend to use a subset of the set "EEPROM," called a "flash EEPROM," because bits aren't erased selectively, but all at once.
Not true. First, the IBM bios was proprietary - it was not a published specification.
Absolutely true. It was published in IBM technical manuals for all to read, and most engineers in the PC hardware business had read them. This put a kink in Compaq's attempt to reverse-engineer, because they had to find engineers for the second team who had never come into contact with the published manuals and could faithfully swear an affidavit stating so.
You made an incorrect statement when you claimed Compaq reverse-engineered that hardware
And I've already told you that I admit that was technically incorrect, although the general meaning (Compaq freed the hardware through reverse engineering) is correct. I wan't careful with the exact words I used, and you jumped all over it.
And lastly, would you please quit making PROM and EPROM possessive with those apostrophes. It's annoying.