Definitely a mistake

By: anon (spam.delete.delete.delete@this.this.this.spam.com), December 22, 2018 2:30 pm
Room: Moderated Discussions
Michael S (already5chosen.delete@this.yahoo.com) on December 22, 2018 7:45 am wrote:
> David Kanter (dkanter.delete@this.realworldtech.com) on December 21, 2018 8:09 am wrote:
> > Michael S (already5chosen.delete@this.yahoo.com) on December 21, 2018 6:39 am wrote:
> > > anon (spam.delete.delete.delete@this.this.this.spam.com) on December 21, 2018 5:30 am wrote:
> > > > Michael S (already5chosen.delete@this.yahoo.com) on December 21, 2018 3:46 am wrote:
> > > > > Maynard Handley (name99.delete@this.name99.org) on December 20, 2018 6:43 pm wrote:
> > > > > > itsmydamnation (no.delete@this.way.com) on December 20, 2018 2:02 pm wrote:
> > > > > > > Anon (Anon.delete@this.anon.com) on December 20, 2018 11:07 am wrote:
> > > > > > > > https://newsroom.ibm.com/2018-12-20-IBM-Expands-Strategic-Partnership-with-Samsung-to-Include-7nm-Chip-Manufacturing
> > > > > > >
> > > > > > > This was the thing i actually wondered about most when GF made the 7nm abandonment announcement.
> > > > > > > How much process development capability does IBM have left? Will IBM work with Samsung
> > > > > > > to develop things like edram for their 7nm process, can it already do it?
> > > > > > >
> > > > > > > Its going to be interesting to exactly what the 7nm power chips look like.
> > > > > >
> > > > > > There are many ways to skin a cat. IBM may perhaps have to give up on-chip eDRAM, but as a replacement they
> > > > > > may be able to use some sort of die-die stacking to put
> > > > > > a massive L3 cache as a separate die under the logic
> > > > > > die. (To goose the performance a little, you could also do mid-90s things like have on-logic-die tags for
> > > > > > the L3, with the L3 data on the separate die, but I don't know if that's worth the hassle.)
> > > > > >
> > > > >
> > > > > There are many ways to skin a power cat. Not so many way for skinning cat360.
> > > > >
> > > > > Traditionally S/360 designer don't trust SRAM for long-term storage.
> > > > > For years their SRAM caches were write-through (their preffered term is store-through)
> > > > > and most recently (z14) they got rid of SRAM caches completely.
> > > >
> > > > I'm pretty sure the L1 is still SRAM.
> > >
> > >
> > > From my copy of "IBM z14 Technical Guide".
> > >
The cache hierarchy (L1, L2, L3, and L4) is implemented with
> > > embedded dynamic random access memory (eDRAM) caches.

> > >
> > > Do you think that's a mistake in the Guide ?
> >
> > Yes. That is 100% a mistake.
>
> My previous copy was draft, but now I downloaded a final version. It says the same.
>
> > DRAM isn't fast enough for the L1 cache.
> >
> > David
> >
>
> The very next sentence: "Until recently, eDRAM was considered to be too slow for this use.
> However, a breakthrough in technology made by IBM has eliminated that limitation."
>
> Also on p.91: "L1 and L2 caches use eDRAM, and are private for each PU core".
>
> p.455 sounds weird: "14nm FINFET SOI technology with IBM embedded
> dynamic static random access memory (eDRAM) technology".
>

It's marketing.
The L2 uses eDRAM and is faster than before because the TLB setup changed and it's all mixed up into one marketing blurb.

My money is on the document that was written by the engineers who designed and built the thing being correct rather than this one.
< Previous Post in ThreadNext Post in Thread >
TopicPosted ByDate
IBM Going with Samsung after dumping GlobalFoundriesAnon2018/12/20 12:07 PM
  IBM Going with Samsung after dumping GlobalFoundriesitsmydamnation2018/12/20 03:02 PM
    IBM Going with Samsung after dumping GlobalFoundriesanon2018/12/20 04:50 PM
    IBM Going with Samsung after dumping GlobalFoundriesMaynard Handley2018/12/20 07:43 PM
      IBM Going with Samsung after dumping GlobalFoundriesMichael S2018/12/21 04:46 AM
        IBM Going with Samsung after dumping GlobalFoundriesanon2018/12/21 06:30 AM
          IBM Going with Samsung after dumping GlobalFoundriesMichael S2018/12/21 07:39 AM
            IBM Going with Samsung after dumping GlobalFoundriesanon2018/12/21 08:24 AM
            Definitely a mistakeDavid Kanter2018/12/21 09:09 AM
              Definitely a mistakeMichael S2018/12/22 08:45 AM
                Definitely a mistakedmcq2018/12/22 11:26 AM
                Definitely a mistakeRobert Williams2018/12/22 11:40 AM
                Definitely a mistakesomeone2018/12/22 01:46 PM
                L1 caches are SRAMDavid Kanter2018/12/22 02:27 PM
                Definitely a mistakeanon2018/12/22 02:30 PM
                Definitely a mistakecarop2018/12/22 08:09 PM
                L1 caches are SRAMjuanrga2018/12/23 05:23 AM
    IBM Going with Samsung after dumping GlobalFoundriesDavid Kanter2018/12/20 09:28 PM
      IBM Going with Samsung after dumping GlobalFoundriesKevin G2018/12/21 08:57 AM
        Samsung fabbed Alpha 21164A chips in 1996/7Mark Roulo2018/12/21 05:24 PM
          Samsung fabbed Alpha 21164A chips in 1996/7Kevin G2018/12/25 03:03 PM
      IBM Going with Samsung after dumping GlobalFoundriesAdrian2018/12/21 11:55 PM
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