DRAM cache

By: wumpus (wumpus.delete@this.lost.in.a.hole), April 8, 2021 8:24 am
Room: Moderated Discussions
Heikki Kultala (heikki.ku.ltala.delete@this.gmail.com) on April 7, 2021 12:38 pm wrote:
> Ganon (anon.delete@this.gmail.com) on March 25, 2021 5:56 pm wrote:
> > My prediction for the immediate future is similar to what is happening today already.
> > Not everyone buys the SKUs with the most core count: it would be silly to pay for cores roughly
> > beyond what you need to saturate the memory bandwidth in aggregate for your workload.
> > DDR5 will allow you to use effectively 2x the core count because it will eventually result in
> > ~2x bandwidth (3200 -> 6400 and bandwidth efficiency improvements). Not sure what will happen
> > after DDR5 though.
> >
> > Don't think a L4 is cost-effective, though IBM does have it in their mainframes. You would probably
> > better off buying 2+ machines with modest core count and
> > DDR5, rather than 1 complex one with L4 cache, HBM, etc.
>
> There is no memory technology called "L4".
>
> L4 just means fourth layer of cache. It can be made with any technology, and
> if it's on separate die, it can be DRAM, which is very cost-effective.
>
> And Intel has it's SRAM-based LLC working as L4 cache for their iGPUs for ages.

I'd expect any DRAM cache to be a custom chip (or at least designed specifically around cache). With a custom chip, you would have all the cachelines of each "way" available and the tag lines all at once. Then the chip would send just the right cacheline.

With standard DRAM (possibly GDDRn or something fast), you'd likely be stuck with a single way (presumably a slew cache or something), but perhaps with a big enough L4 it would justify such a cache.
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TopicPosted ByDate
Intel's IDM 2.0 announcementJon Masters2021/03/23 03:31 PM
  Intel's IDM 2.0 announcementRayla2021/03/23 03:45 PM
    Intel's IDM 2.0 announcementdmcq2021/03/23 04:30 PM
    commitment to foundry, shutting down fabless talkDaniel B2021/03/23 04:46 PM
      commitment to foundry, shutting down fabless talkKester L2021/03/23 04:56 PM
        commitment to foundry, shutting down fabless talkanonymou52021/03/24 12:57 AM
          commitment to foundry, shutting down fabless talkme2021/03/24 03:25 AM
            commitment to foundry, shutting down fabless talkJoe2021/03/24 05:56 AM
              commitment to foundry, shutting down fabless talkMichael S2021/03/24 06:47 AM
                commitment to foundry, shutting down fabless talkme2021/03/24 07:04 AM
      commitment to foundry, shutting down fabless talkJames2021/03/24 03:39 AM
        Intel gutted 7 nmme2021/03/24 03:48 AM
          Intel gutted 7 nmDoug S2021/03/24 08:20 AM
            Intel gutted 7 nmanon2021/03/25 12:43 PM
              Intel gutted 7 nmeh2021/03/26 02:36 AM
                Intel gutted 7 nmAdrian2021/03/26 08:58 AM
                  Intel gutted 7 nmwumpus2021/03/26 09:53 AM
                  Intel gutted 7 nmme2021/03/26 10:11 AM
                  Intel gutted 7 nmMaxwell2021/03/26 02:21 PM
                    Intel gutted 7 nmYoav2021/03/29 01:06 AM
              Intel gutted 7 nmDoug S2021/03/26 09:43 AM
                Intel gutted 7 nmanon2021/03/26 03:39 PM
                  Intel gutted 7 nmNoSpammer2021/03/26 08:46 PM
                    Intel gutted 7 nmAdrian2021/03/26 11:57 PM
                      Intel gutted 7 nmAndrey2021/03/28 06:18 PM
                    Intel gutted 7 nmanon2021/03/27 05:52 AM
                    Intel gutted 7 nmwumpus2021/03/27 12:16 PM
                  Intel gutted 7 nmDoug S2021/03/27 05:08 PM
                    Intel gutted 7 nmanon2021/12/13 03:05 PM
                      Intel gutted 7 nm---2021/12/13 04:31 PM
                      Intel gutted 7 nmDoug S2021/12/13 09:34 PM
                        Intel gutted 7 nmanon2021/12/13 10:41 PM
                          Intel gutted 7 nmDoug S2021/12/14 11:38 AM
                            Intel gutted 7 nmanon2021/12/14 11:58 AM
                            Feed the Troll less (unless you are enjoying it!)Mark Roulo2021/12/14 01:52 PM
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                  Intel gutted 7 nmme2021/03/27 12:22 PM
                  Intel gutted 7 nmDoug S2021/03/27 05:14 PM
                    Intel gutted 7 nmDavid Kanter2021/04/07 09:06 PM
                      Intel gutted 7 nmDoug S2021/04/08 12:38 PM
        commitment to foundry, shutting down fabless talkDaniel B2021/03/24 08:08 AM
      commitment to foundry, shutting down fabless talkDoug S2021/03/24 08:12 AM
      commitment to foundry, shutting down fabless talkMaxwell2021/03/25 11:16 AM
        commitment to foundry, shutting down fabless talkme2021/03/25 11:38 AM
          commitment to foundry, shutting down fabless talkAdrian2021/03/25 01:01 PM
            commitment to foundry, shutting down fabless talkme2021/03/27 12:57 PM
    A lot has changed since thenDoug S2021/03/24 08:01 AM
    Intel's IDM 2.0 announcementGabriele Svelto2021/03/25 03:17 AM
  Intel's IDM 2.0 announcementBeastian2021/03/23 05:39 PM
    Intel's IDM 2.0 announcementJames2021/03/24 03:14 AM
      Intel's IDM 2.0 announcementme2021/03/24 03:37 AM
        Intel's IDM 2.0 announcementJames2021/03/24 03:53 AM
      Intel's IDM 2.0 announcementanonymou52021/03/24 08:39 AM
    Intel's IDM 2.0 announcementJukka Larja2021/03/24 06:05 AM
    Intel's IDM 2.0 announcement - Hyper-scalers as customersBjörn Ragnar Björnsson2021/03/24 06:19 PM
  5nm the end of DRAM?Brett2021/03/25 05:17 PM
    What is next after DDR5?Ganon2021/03/25 05:56 PM
      What is next after DDR5?wumpus2021/03/26 09:10 AM
        What is next after DDR5?Brett2021/03/26 04:39 PM
          What is next after DDR5?wumpus2021/03/28 10:44 AM
      What is next after DDR5?Brett2021/03/27 04:27 PM
        What is next after DDR5?Doug S2021/03/27 05:18 PM
      What is next after DDR5?Anononymous Coward2021/03/30 07:03 AM
        What is next after DDR5?Andrey2021/03/30 09:09 AM
          What is next after DDR5?David Hess2021/04/04 08:52 PM
      What is next after DDR5?David Hess2021/04/04 08:45 PM
        What is next after DDR5?Doug S2021/04/05 06:57 AM
          What is next after DDR5?David Hess2021/04/05 10:45 AM
          Same costAnon2021/04/05 11:31 AM
            Same costDavid Hess2021/04/05 08:26 PM
            Same costMaxwell2021/04/06 07:17 PM
              Same costDavid Hess2021/04/07 02:35 PM
          What is next after DDR5?wumpus2021/04/07 09:06 AM
      L4 is not a memory technologyHeikki Kultala2021/04/07 12:38 PM
        DRAM cachewumpus2021/04/08 08:24 AM
        Intel iGPU memory was eDRAM, not SRAMMark Roulo2021/04/08 11:31 AM
          I am not talking about the eDRAM. I am talking about the cache that is L3 for CPUHeikki Kultala2021/04/08 11:09 PM
            I am not talking about the eDRAM. I am talking about the cache that is L3 for CPURobert Williams2021/04/09 11:24 AM
              This STILL has NOTHING to do with the eDRAM. I am talking about the SRAM LLCHeikki Kultala2021/04/09 12:57 PM
                This STILL has NOTHING to do with the eDRAM. I am talking about the SRAM LLC---2021/04/09 01:40 PM
    5nm the end of DRAM?Rayla2021/03/26 09:28 AM
      5nm the end of DRAM?riy2021/04/08 06:26 AM
        5nm the end of DRAM?Michael S2021/04/08 11:51 AM
    5nm the end of DRAM?Doug S2021/03/26 09:52 AM
      5nm the end of DRAM?wumpus2021/04/07 09:10 AM
        5nm the end of DRAM?Robert Williams2021/04/07 11:05 AM
    Totaly misunderstanding of DDR SDRAM memory interfaces and DRAMHeikki Kultala2021/04/07 12:36 PM
      Totaly misunderstanding of DDR SDRAM memory interfaces and DRAManonymou52021/04/07 01:13 PM
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