3 ms·

The whole system was designed for long battery life and standby time. That’s why it didn’t have the backlight LCD, had an enormous battery (reading https://supp

The whole system was designed for long battery life and standby time. That’s why it didn’t have the backlight LCD, had an enormous battery (reading https://support.apple.com/kb/sp140?locale=en_GB https://support.apple.com/kb/sp140?locale=en_GB, it only delivered 5W, tops, though), and used static RAM. I guess this expansion used dynamic RAM with on-board refresh logic, but the page isn’t clear (to me) on that.

duskwuff 3y ago
> I guess this expansion used dynamic RAM with on-board refresh logic, but the page isn’t clear (to me) on that. It's a little bit of both. The RAM on the expansion card is an ISSI pseudo-SRAM: https://www.digikey.com/en/products/detail/issi-integrated-silicon-solution-inc/IS66WVE4M16EBLL-70BLI/6202023 https://www.digikey.com/en/products/detail/issi-integrated-s... In short, it's DRAM on the inside, but all of the refresh logic is internal, so it behaves as if it were static RAM.
- Androda 3y ago
  Hey cool, my RAM card is being mentioned on hacker news! You're right, the card uses PSRAM because non-synchronous SRAM chips basically aren't available new any more. I didn't want to have to troll the depths of (semi-questionable) new old stock parts sites and went with new chips. This design was assisted by my good friend techknight, original designer of the 8 megabyte RAM card for the mac portable.
  - classichasclass 3y ago
    (author) It worked great. You deserve it! Thanks for making it.
  - kjs3 3y ago
    I just bought a dozen new PDIP Alliance AS6C4008 512k x 8 asych srams from Mouser from stock. If you go surface mount, I think there are even more options.
  - rasz 3y ago
    >PSRAM because non-synchronous SRAM chips basically aren't available new any more. AS6C6416 4Mx16. Someone even uses it raw on 5V bus with no level translation, just tiny Lattice LC4064V cpld for address decoding. https://www.amigalove.com/viewtopic.php?f=6&t=1689 https://www.amigalove.com/viewtopic.php?f=6&t=1689 https://hackaday.com/2021/01/08/the-amiga-1000-still-receiving-new-peripherals-35-years-later/#comment-6309849 https://hackaday.com/2021/01/08/the-amiga-1000-still-receivi...
    - Androda 3y ago
      Yeah, I noticed that chip and didn't give it a second look. It's more than 3x the cost of the PSRAM solution, and that would have driven up the price of the RAM card higher than planned. So sure, it exists. And that's about all I have to say about it.
adamzegelin 3y ago
Impressive that Apple keeps support documentation for such old products.

duskwuff 3y ago

> I guess this expansion used dynamic RAM with on-board refresh logic, but the page isn’t clear (to me) on that. It's a little bit of both. The RAM on the expansion card is an ISSI pseudo-SRAM: https://www.digikey.com/en/products/detail/issi-integrated-silicon-solution-inc/IS66WVE4M16EBLL-70BLI/6202023 https://www.digikey.com/en/products/detail/issi-integrated-s... In short, it's DRAM on the inside, but all of the refresh logic is internal, so it behaves as if it were static RAM.

Androda 3y ago
Hey cool, my RAM card is being mentioned on hacker news! You're right, the card uses PSRAM because non-synchronous SRAM chips basically aren't available new any more. I didn't want to have to troll the depths of (semi-questionable) new old stock parts sites and went with new chips. This design was assisted by my good friend techknight, original designer of the 8 megabyte RAM card for the mac portable.
- classichasclass 3y ago
  (author) It worked great. You deserve it! Thanks for making it.
- kjs3 3y ago
  I just bought a dozen new PDIP Alliance AS6C4008 512k x 8 asych srams from Mouser from stock. If you go surface mount, I think there are even more options.
- rasz 3y ago
  >PSRAM because non-synchronous SRAM chips basically aren't available new any more. AS6C6416 4Mx16. Someone even uses it raw on 5V bus with no level translation, just tiny Lattice LC4064V cpld for address decoding. https://www.amigalove.com/viewtopic.php?f=6&t=1689 https://www.amigalove.com/viewtopic.php?f=6&t=1689 https://hackaday.com/2021/01/08/the-amiga-1000-still-receiving-new-peripherals-35-years-later/#comment-6309849 https://hackaday.com/2021/01/08/the-amiga-1000-still-receivi...
  - Androda 3y ago
    Yeah, I noticed that chip and didn't give it a second look. It's more than 3x the cost of the PSRAM solution, and that would have driven up the price of the RAM card higher than planned. So sure, it exists. And that's about all I have to say about it.

adamzegelin 3y ago

Impressive that Apple keeps support documentation for such old products.