3 ms·

It was earlier than the 90s, and came with popular 8-bit CPUs in the 80s. The Z-80 microprocessor could address 64kb (which was 65,536 bytes) on its 16-bit addr

It was earlier than the 90s, and came with popular 8-bit CPUs in the 80s. The Z-80 microprocessor could address 64kb (which was 65,536 bytes) on its 16-bit address bus. Similarly, the 4104 chip was a "4kb x 1 bit" RAM chip and stored 4096 bits. You'd see this in the whole 41xx series, and beyond.

pdw 8mo ago
Even then it was not universal. For example, that Apple I ad that got posted a few days ago mentioned that "the system is expandable to 65K". https://upload.wikimedia.org/wikipedia/commons/4/48/Apple_1_Advertisement_Oct_1976.jpg https://upload.wikimedia.org/wikipedia/commons/4/48/Apple_1_...
- wvenable 8mo ago
  Seems like a typo given that the ad contains many mentions of K (8K, 32K) and they're all of the 1024 variety.
  - duskwuff 8mo ago
    If you're using base 10, you can get "8K" and "32K" by dividing by 10 and rounding down. The 1024/1000 distinction only becomes significant at 65536.
    - wvenable 8mo ago
      Still the advertisement is filled with details like the number of chips, the number of pins, etc. If you're dealing with chips and pins, it's always going to base-2.
- kstrauser 8mo ago
  Someone here the other day said that it could accept 64KB of RAM plus 1KB of ROM, for 65KB total memory. I don't know if that's correct, but at least it'd explain the mismatch.
magicalist 8mo ago
> The Z-80 microprocessor could address 64kb (which was 65,536 bytes) on its 16-bit address bus. I was going to say that what it could address and what they called what it could address is an important distinction, but found this fun ad from 1976[1]. "16K Bytes of RAM Memory, expandable to 60K Bytes", "4K Bytes of ROM/RAM Monitor software", seems pretty unambiguous that you're correct. Interestingly wikipedia at least implies the IBM System 360 popularized the base-2 prefixes[2], citing their 1964 documentation, but I can't find any use of it in there for the main core storage docs they cite[3]. Amusingly the only use of "kb" I can find in the pdf is for data rate off magnetic tape, which is explicitly defined as "kb = thousands of bytes per second", and the only reference to "kilo-" is for "kilobaud", which would have again been base-10. If we give them the benefit of the doubt on this, presumably it was from later System 360 publications where they would have had enough storage to need prefixes to describe it. [1] https://commons.wikimedia.org/wiki/File:Zilog_Z-80_Microprocessor_ad_May_1976.jpg https://commons.wikimedia.org/wiki/File:Zilog_Z-80_Microproc... [2] https://en.wikipedia.org/wiki/Byte#Units_based_on_powers_of_10_(SI_Prefixes) https://en.wikipedia.org/wiki/Byte#Units_based_on_powers_of_... [3] http://www.bitsavers.org/pdf/ibm/360/systemSummary/A22-6810-0_360sysSummary64.pdf#page=6 http://www.bitsavers.org/pdf/ibm/360/systemSummary/A22-6810-...

pdw 8mo ago

Even then it was not universal. For example, that Apple I ad that got posted a few days ago mentioned that "the system is expandable to 65K". https://upload.wikimedia.org/wikipedia/commons/4/48/Apple_1_Advertisement_Oct_1976.jpg https://upload.wikimedia.org/wikipedia/commons/4/48/Apple_1_...

wvenable 8mo ago
Seems like a typo given that the ad contains many mentions of K (8K, 32K) and they're all of the 1024 variety.
- duskwuff 8mo ago
  If you're using base 10, you can get "8K" and "32K" by dividing by 10 and rounding down. The 1024/1000 distinction only becomes significant at 65536.
  - wvenable 8mo ago
    Still the advertisement is filled with details like the number of chips, the number of pins, etc. If you're dealing with chips and pins, it's always going to base-2.
kstrauser 8mo ago
Someone here the other day said that it could accept 64KB of RAM plus 1KB of ROM, for 65KB total memory. I don't know if that's correct, but at least it'd explain the mismatch.

magicalist 8mo ago

> The Z-80 microprocessor could address 64kb (which was 65,536 bytes) on its 16-bit address bus. I was going to say that what it could address and what they called what it could address is an important distinction, but found this fun ad from 1976[1]. "16K Bytes of RAM Memory, expandable to 60K Bytes", "4K Bytes of ROM/RAM Monitor software", seems pretty unambiguous that you're correct. Interestingly wikipedia at least implies the IBM System 360 popularized the base-2 prefixes[2], citing their 1964 documentation, but I can't find any use of it in there for the main core storage docs they cite[3]. Amusingly the only use of "kb" I can find in the pdf is for data rate off magnetic tape, which is explicitly defined as "kb = thousands of bytes per second", and the only reference to "kilo-" is for "kilobaud", which would have again been base-10. If we give them the benefit of the doubt on this, presumably it was from later System 360 publications where they would have had enough storage to need prefixes to describe it. [1] https://commons.wikimedia.org/wiki/File:Zilog_Z-80_Microprocessor_ad_May_1976.jpg https://commons.wikimedia.org/wiki/File:Zilog_Z-80_Microproc... [2] https://en.wikipedia.org/wiki/Byte#Units_based_on_powers_of_10_(SI_Prefixes) https://en.wikipedia.org/wiki/Byte#Units_based_on_powers_of_... [3] http://www.bitsavers.org/pdf/ibm/360/systemSummary/A22-6810-0_360sysSummary64.pdf#page=6 http://www.bitsavers.org/pdf/ibm/360/systemSummary/A22-6810-...