SRAM compatibility

Discussion in 'General Electronics Chat' started by EdGs, Mar 10, 2011.

  1. EdGs

    Thread Starter New Member

    Mar 10, 2011
    Are faster SRAM chips backwards-compatible with their slower counterparts in the same series? For example: a 6116LP-3 in place of a 6116LP-4?

    Does the same hold true for 2114's, 6514's, etc.?

    If they are, is there a limit? I got a bit confused when comparing datasheets. I am working on an old synthesizer and trying to build up an assortment of spare parts for the future. It has a Z80 running at 2.5 MHz. as the processor. It has an HM6116LP-4, a couple D444C-5614's, and a couple M5L-2114LP-3.

    In the case of the 6514's I came across some D444C-6514-2 chips and it got me a bit curious about this.

  2. SgtWookie


    Jul 17, 2007
    Interesting that they used SRAM, as the onboard DRAM refresh was a feature of the Z80's; allowing easy use of the much less expensive dynamic RAM.

    In modern PC's you can frequently use faster DDR memory than called for; the bottleneck will be the slowest RAM installed. I tried using some faster DRAMs (4164's) in an old TRS-80 Model 4P; 150nS vs 200nS, but after a few minutes of operation, the faster DRAM would lose it's memory.

    Your timing for asking these questions couldn't be worse, because after dragging all of my old Z80 and TRS-80 books around for the last 20-30 years, I donated them to a school about 3 hours ago. Sorry about that.
  3. tom66

    Senior Member

    May 9, 2009
    This doesn't apply to modern computers as each RAM is given a separate clock. I know I use 800 MHz memory in one of my gaming computers, it's so fast it has a little heat spreader on it. But there is also a 333 MHz cheapie RAM in there in place of one of the 800's that died, and it still runs full speed.
  4. EdGs

    Thread Starter New Member

    Mar 10, 2011
    Thanks, I'll have to dig into the service manual for this some more. This machine was built in 1982, so very old tech. It was very advanced for its time, and still very sought after. I believe the 6116 stores the sound patches and the 2114's act as a scratchpad for the knobs, keys,etc. The 6514's transfer their settings to the 2114's. I did already use a 6116lp-3 instead of lp-4 and it appears to work fine, I just got a bit curious the more I thought about things.