Lunar Modules and cellphones

November 30, 2012 8:34 AM

1) How much memory did the Apollo Lunar Module (LM) have and 2) when was the first cellphone with the same amount of memory introduced to the public? 3) Where there any other publicly available products that had the same amount of memory? 4) If so, when were they introduced to the market?

This may be a bit of a tricky question in terms defining what computer memory and the fact that that the Apollo Flight Guidance Computer (AGC) had two kinds of memory, fixed and erasable.

My understanding is that the software to run the LM was in the fixed type of memory on the craft. So I'm specifically looking for which cellphone had a similar amount of memory to run its OS. It may have had more for the user to store numbers or later photos, but I'm just interested in the amount of memory that would be needed to store the OS that ran the phone.

posted by Brandon Blatcher to Technology (6 answers total)

So Wikipedia's article on the Apollo Guidance Computer says that the Lunar Module had "a single DSKY for its AGC", from which I extrapolate that the Lunar Module had an AGC. That article says 2k words of rewritable memory, and 36k words of read only memory. Words were approximately 16 bits, so that's 4k bytes of rewritable and 72k bytes of read-only.

So now the question is how to compare that to phones. In looking at cell phone technology, it looks as though you could build an AMPS phone with strictly analog components. Looks like GSM and SMS emerged at about the same time, 1991 to 1992. That's an era where I could imagine embedded devices still only having 16k or so of ROM, but 4k is less than 25 stored SMS messages, so the first SMS phone (circa 1992) probably had more rewritable storage, and may or may not have had as much read-only memory.
posted by straw at 8:46 AM on November 30, 2012

Apollo Guidance Computer had 2 k RAM and 36 k ROM.

In 1975, the Altair 8800 was available as a kit, with 256 bytes memory up to 64 k.

The first cell phone was demonstrated in 1973 and became a commercial product in 1982. Its memory could store 30 phone numbers ... so that's less than 1 K; I suspect that the memory for the operating system (in rom) was significantly higher.
posted by aroberge at 8:49 AM on November 30, 2012

3) Where there any other publicly available products that had the same amount of memory?

This thread had some information on memory in arcade/Atari gaming systems.
posted by doctord at 9:55 AM on November 30, 2012

aroberge, as I noted the 2k and 36k were 16 bit words, double-bytes. And that first cell phone could have been built with discrete logic. Even with the A-D DTMF keys (keys that occurred occasionally in those days) that's 150 bytes, and recall and dial are just a counter shifting that data out to display drivers and modulators, respectively.

I did a little exploratory work for a POCSAG pager in 1992, and I think we were talking about an 8051 compatible chip with 16k bytes of ROM doing the thinking, though it may have been 4k. The microcontroller revolution was just starting then, the BASIC Stamp hit in 1992, Atmel's 8051 compatible device with integrated flash didn't hit 'til 1993, so it was still a matter of "as little external ROM as you can possibly squeeze your application into".

Which may actually argue for slightly later than '92.
posted by straw at 9:58 AM on November 30, 2012

AC powered or battery/portable?

General purpose computers usually had only enough ROM to boot from floppy, then lots of RAM for code & data. 64K might have been max for a boat anchor in 1975, but it wasn't long before you could get more than 72K bytes for your S-100 bus machine in 1982 (CompuPro RAM 21 with 128K. Bank switched for 8 bit data bus/16 bit address bus CPUs).

Looks like programmable calculators and "pocket computers" were ahead of cell phones & pagers in the "max RAM in pocket size + battery powered" category: HP-75 in 1982 had "48 KiB system ROM and 16 KiB RAM" but could hold 3 more ROM modules.

If you insist on 36k x16 of ROM rather than 76K bytes total of any kind of storage, fixed-function devices like a Gameboy + cartridge had 16K RAM + minimum 256K ROM in 1989.
posted by morganw at 5:11 PM on November 30, 2012

Engine controllers in the early 80's had around 8 KB of ROM and 256 bytes of RAM. The ones I worked with had custom Motorola 8 bit micros.
posted by rfs at 7:15 PM on November 30, 2012