Talk:Intel MCS-48

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8048 Oral Panel[edit]

Interview with 8048 designers. Is the link worthwhile enough to be included in the 8048 page? I leave the decision to wikipedia maintainers (this note added 2010-01-16)

8048 the 1st µC?[edit]

Was it really _the_first_ microcontroller? Are the ROM and RAM both on-chip?--Anonymous

Thanks for the highly relevant questions. The 8048 was Intel's first µC but the TMS 1000 is reported to have been the first µC as such. And the ROM was in fact external; this is now corrected in the article. --Wernher 16:15, 5 Apr 2004 (UTC)

8049's internal ROM[edit]

To my best knownledge the 8049 DOES have internal ROM, consult the relevant Intel device datasheets if you don't believe me (note that IBM AT Keyboards manufacturered before 1996 usually have this MCU, and i have never encountered a KB with ROM on-board :-D :lol:) -- BKiL 19:41, 12 Nov 2004 (UTC)
Device  Internal     Memory
8035AHL none         64 x 8 RAM
8039AHL none        128 x 8 RAM
8040AHL none        256 x 8 RAM
8048AH  1K x 8 ROM   64 x 8 RAM
8049AH  2K x 8 ROM  128 x 8 RAM
8050AH  4K x 8 ROM  256 x 8 RAM
P8748H  1K x 8 PROM  64 x 8 RAM
P8749H  2K x 8 PROM 128 x 8 RAM

*note:  PROM = Programmable ROM

Thanks for the table; I guess we'll have to fix the article (again) then... :-) --Wernher 21:34, 12 Nov 2004 (UTC)
According to the IBM documentation for the original PC (available from the Retrocomputing Archive - - the original IBM PC keyboards actually have an 8048 in them for generating the scan-codes. -- Dshadowwolf (talk) 04:45, 25 March 2009 (UTC)

Table added --JWBE (talk) 16:31, 4 September 2010 (UTC)


Arnim, are you sure they had EPROM? I am aware of manufacturers selling EPROM ICs as OTP PROM to save packaging costs, but the datasheet I had didn't mention anything about UV lignt, nor EPROM! Of course they _could_ have made enhanced versions since, but this would require us to make note of this fact, wouldn't it? Like the original i8051 had external ROM, but a (much) later clone named AT89C2051 had Flash. -- BKiL 22:03, 26 Dec 2004 (UTC)

Yes, there is one with EPROM. I took a picture of one a put it on the page. - Bryce

Haven't checked back for quite a while, sorry. Just for completeness, now that Bryce posted the picture: Intel (and others) manufactured the 8749 with EPROM in ceramic packages with UV window. I have several of these 8748/8749 (both Intel and NEC) floating around here. Intel also documented this capability in their data sheet(s). Nevertheless, it is possible that there are variants with OTP EPROM or even "real" PROM. I agree that PROM should be mentioned if we have information about such devices. - Arnim
Finally found a datasheet which mentions an 8648 with "One-Time Factory Programmable EPROM". I had a 8648 for years but never had a clue what it might be. Interesting to see that it has a ceramic package with UV window [1]. Unfortunately, the datasheet does not tell anything more about this one, the above description is all I have.
My understanding is that it was used like an 8048 by the customer but Intel programmed the OTP EPROM before delivery. Why this when there's an 8748? Maybe they intended to stock blank chips and quickly provide 8048-like samples. Fabricated 8048 always contain the ROM mask thus being specific for the customer (in contrast to "general purpose" 8648). - Arnim

Further Derivatives[edit]

The hunt for the PROM version revealed information about other derivatives. The updated table contains additional UPIs. -- Arnim

Device  Internal           Memory       Remarks
8021    1K x 8 ROM         64 x 8 RAM   Subset of 8048, 28 pins
8041    1K x 8 ROM         64 x 8 RAM   Universal Peripheral Interface (UPI)
8041AH  1K x 8 ROM        128 x 8 RAM   UPI
8741A   1K x 8 EPROM       64 x 8 RAM   UPI, EPROM version of 8041
8741AH  1K x 8 OTP EPROM  128 x 8 RAM   UPI, OTP EPROM version of 8041AH
8042AH  2K x 8 ROM        256 x 8 RAM   UPI
8742    2K x 8 EPROM      128 x 8 RAM   UPI, EPROM version
8742AH  2K x 8 OTP EPROM  256 x 8 RAM   UPI, OTP EPROM version of 8042AH
8648    1k x 8 OTP EPROM   64 x 8 RAM   Factory OTP EPROM

Table added --JWBE (talk) 16:31, 4 September 2010 (UTC)

"OTP EPROM"?[edit]

This seems like very odd language - an EPROM that can actually only be programmed once screams "PROM" to me. Unless we're getting our acronyms mixed up, it's electronically programmable, and someone's therefore knocked out the second E ("erasable") of EEPROM rather than the first?

Given the discussion above, does anyone mind if I'm "bold" and just change that? If the Intel spec sheets actually do say "OTP EPROM" then feel free to revert it... (talk) 11:05, 16 March 2014 (UTC)

You're right, the "OTP" makes the EPROM a "PROM" (but it's not derived from an EEPROM, but rather from an UV-erasable EPROM). The term "OTP EPROM" provides more information than just PROM, because there's many technical variants of a PROM (e.g. bipolar fusable...). Here we're talking about an EPROM (which could be erased optically!), but since it does not have an opaque window, the UV-light could not reach the memory cell. Hence it's an "OTP". --Wosch21149 (talk) 10:14, 17 March 2014 (UTC)


OTP = One Time programable's are a form of mask programmable rom that are written one time and cannot be written again.

OTP's use byte width fusible links (8 fuse links per byte per memory location) which are blown "open to create logic "0" and unblown to maintain a logic "1", these are known More commonly as PROMS and were the earliest form of permanent code/data storage for micro controllers & microprocessors until UV erased memory devices called eproms came along in the mid 1970's and remained the standard for programmable devices up till the early 1990's.

At which time a newer memory device type called EEPROM that used electrical current to both program and erase a memory device instead of UV light. these devices gave birth to what we see today Serial EEPROM & Serial Flash memories etc — Preceding unsigned comment added by (talk) 08:10, 25 February 2015 (UTC)


MIPS usually refers to performance relative to a VAX 11/780 not literal instructions, and most instructions don't execute in one cycle anyway. (talk) 01:43, 23 May 2017 (UTC)