Sunday, 2023-09-03

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markos_lkcl, thought about that, reg. the the double-width-shift, maddrs/msubrs could be used for that purpose, for left shifts we coudl either a) use left shifts with negative immediate values, or b) provide maddls/msubls11:26
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openpowerbot[irc] <sadoon[m]1>
openpowerbot[irc] <sadoon[m]1> Another good resource re: DDR4, will read it later today11:51
openpowerbot[irc] <sadoon[m]1> Sorry IRC guys, let me fix that11:51
openpowerbot[irc] <sadoon[m]1>
openpowerbot[irc] <sadoon[m]1> Another good resource re: DDR4, will read it later today11:51
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openpowerbot[irc] <sadoon[m]1> Just read it, the more I read about modern DRAM architectures, it seems the best option14:37
openpowerbot[irc] <sadoon[m]1> Is to implement an older version14:37
openpowerbot[irc] <sadoon[m]1> There aren't massive changes between revisions from a controller standpoint, but it did get more complicated with DDR414:38
openpowerbot[irc] <sadoon[m]1> If we have DDR2/3 for example, DDR4 would be say 20-30% more work?14:39
openpowerbot[irc] <sadoon[m]1> Etc14:39
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openpowerbot[irc] <cesar[m]1> sadoon, interesting find about the low clock speed DDR3 controller.15:36
openpowerbot[irc] <sadoon[m]1> Yes that's definitely useful15:37
openpowerbot[irc] <cesar[m]1> The repository as a whole doesn't have a license file, but the header in each file indicates the Apache2 license.15:37
openpowerbot[irc] <sadoon[m]1> But again we can't use it easily without contacting the developer15:37
openpowerbot[irc] <sadoon[m]1> cesar[m]1: Ah, nice catch!15:38
openpowerbot[irc] <sadoon[m]1> If that's the case then good15:38
markos_well, even then, we can use it, internally, and see if it's working, and if it does, then we can contact the developer and get a friendly open source license to libresoc15:40
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openpowerbot[irc] <sadoon[m]1> And DDR3 is dirt cheap anyways16:17
openpowerbot[irc] <programmerjake> Apache 2 is explicitly compatible with GPLv3 iirc, so we wouldn't need to ask them to relicense it16:46
openpowerbot[irc] <programmerjake> since our HDL is all LGPLv316:46
openpowerbot[irc] <sadoon[m]1> Cesar was also right, it's indeed Apache but the maintainer forgot to put a LICENSE file16:48
openpowerbot[irc] <programmerjake>
openpowerbot[irc] <sadoon[m]1> It's been abandoned so we might have to pick up where they left off16:48
openpowerbot[irc] <sadoon[m]1> "currently supports Xilinx 7 series (Artix, Kintex) and Lattice ECP5 FPGAs"16:49
openpowerbot[irc] <sadoon[m]1> Also very good for us16:49
cesarHey, I've arranged to give you a nice demontration of that CNC machine we've been building, for the next Tuesday meeting.17:52
openpowerbot[irc] <programmerjake> nice!17:56
cesarIt seems we were able to iron out most of the kinks.17:56
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openpowerbot[irc] <sadoon[m]1> Awesome19:15
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lkclcesar, oooo!19:49
lkclmarkos_, fantastic.19:50
lkclbtw when you create those bugreports (specific for ed25519) i can provide the relevant insights, i don't want to... well i could mention them here19:51
lkclbasically the "low-level primitives" - jacob and i did Knuth Algorithm D and M - are already there19:51
lkclwe just didn't get round to doing an actual port/demo of Knuth D or M19:51
lkclbut unit test demos *of* the actual instructions *for* implementing long-multiply and long-divide by using SVP64 to do *all* of one of the inner-loops19:52
lkcl(thus reducing M and D to a single outer-loop if you have a fixed register-width)19:53
lkclare all done (almost a year ago now)19:53
lkclaw doh19:53
lkcl1 sec19:53
lkclvector-vector add (and correspondingly vector-vector sub) is brain-dead-simple.19:55
lkclthis is double-width-shift-left:20:02
lkclRB - the amount to shift20:02
lkcl    (RA || RC) << RB => (RS || RT)20:06
lkcland when chained-together, RS is the carry-out which becomes the 64-bit-wide carry-in to RC20:06
lkcli'm not entiiirely sure how to express that RA || RC should be an *addition*... ermermerm...20:07
lkclit *could* be as simple as:20:08
lkcl  87     RT <- (v[0:63] & mask) | ((RC) & ¬¨mask)20:08
lkcl  87     RT <- (v[0:63] & mask) | (RC)20:08
lkcl  87     RT <- (v[0:63] & mask) + (RC)20:08
lkclhonestly i have been slightly caught off-guard by the Haskell ed25519 routine because it is in what is known as "carry-save" format20:10
lkcli.e. rather than what you normally do in long-multiplication, when you do each digit multiply you always always right there right then do a carry-ripple right the way through the intermediary result20:11
lkclyou instead save *both* digits of each of the 1-digit long-multiply (9x9==81 for example, you save *81* rather than "write down the 1 and ripple-carry-the-8")20:12
lkclthen perform all of the needed adds *afterwards* as a completely separate step.20:13
lkcli never analysed that algorithm so have no idea what arithmetic primitives are actually needed20:14
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lkcl edited20:27
lkclnggggh.... yyyeahhh...
lkcladd128_64 is simply being used as a standard 64-bit-carry-aware-add (where "carry" is a single bit)20:37
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lkclno wait...20:40
lkclit's a 128-bit in, plus a 64-bit in, where the result is 128-bit BUT the hi-half obviously only rolls over by a single bit carry-in20:41
lkclfor which, i think, annoyingly, we'd need like... 4-in 3-out to cover that with 64-bit regs20:42
lkclbecause it's a 128-bit input (2in) plus a 64-bit input (1-in) shifted by a fixed-amount (hmmm ok just 3-in) producing a 128-bit result (2-out) but with a... a... oh hang on it *might* be possible20:44
lkcljust incredibly expensive in terms of operands (because the shift-amount as an immediate is another 5 bits)20:45
openpowerbot[irc] <sadoon[m]1> Guys there's someone offering their Blackbird with an 8-core for sale20:46
openpowerbot[irc] <sadoon[m]1> It's cheseman on Talos_Workstation20:46
openpowerbot[irc] <sadoon[m]1> If you have the funds do pick it up, will be very useful20:46
lkcltoshywoshy ^20:47
openpowerbot[irc] <sadoon[m]1> I wish I could take it myself but I don't have the budget rn20:47
openpowerbot[irc] <sadoon[m]1> Speaking of which, toshywoshy:  your 8-core should be in the UK within a week or so20:48
openpowerbot[irc] <sadoon[m]1> Missed my brother's flight but luckily his roommate leaves soon so I'll hand it to him instead20:48
openpowerbot[irc] <sadoon[m]1> I skimmed through the DDR3 source from the repo I sent, looks good so far20:49
openpowerbot[irc] <sadoon[m]1> We might be in luck if this works20:49
openpowerbot[irc] <sadoon[m]1> Especially since it's designed with Xilinx boards in mind20:50
openpowerbot[irc] <lkcl_> sadoon[m]1,
openpowerbot[irc] <lkcl_> already done. multiple times.20:51
openpowerbot[irc] <sadoon[m]1> Wow, another gold mine20:51
openpowerbot[irc] <lkcl_> and associated firmware for training
openpowerbot[irc] <sadoon[m]1> Can these run at very low clocks though like the DDR3 one?20:53
openpowerbot[irc] <lkcl_> please - really - don't spend excessive time on this, apart from learning/confirming that yes, it is an absolutely massive costly project whatever the route chosen20:54
openpowerbot[irc] <lkcl_> that's what LPDDR4/5 are specifically designed to do, yes.20:54
openpowerbot[irc] <sadoon[m]1> If the bulk of the work has already been done, we might just be in luck Luke :)20:54
openpowerbot[irc] <lkcl_> there are *additional commands* added over-and-above the DDR3 command-set that crank the clock rate down20:54
openpowerbot[irc] <sadoon[m]1> No need to reinvent the wheel20:54
openpowerbot[irc] <lkcl_> no... you're not quite following and i have spent too long explaining this multiple times, so please don't keep asking me to do it, please "prune this branch of investigation"20:55
openpowerbot[irc] <lkcl_> *even the verification and testing* is itself massively-expensive20:55
openpowerbot[irc] <lkcl_> when you have a "working" PHY *just getting it up and running* - no modifications just doing simulations and FPGA bringup - is incredibly costly20:56
openpowerbot[irc] <lkcl_> you normally think in terms of a software library, "just built it, read the API, plug it in to my app and get going"20:58
openpowerbot[irc] <lkcl_> that's nooowheeerre near an appropriate "handle / assumption" to begin from, unfortunately: it's a yawning chasm20:58
openpowerbot[irc] <lkcl_> plus in that particular case, "PHY" is just the "interface to the DRAM IC". it is *not* also the *controller*.21:01
openpowerbot[irc] <sadoon[m]1> If someone has created a fully functional memory controller for board X, we could use Jacob's idea of interfacing and then all the testing we need to do would be to connect up the two boards21:01
openpowerbot[irc] <lkcl_> there is an interface called... DFI21:01
openpowerbot[irc] <sadoon[m]1> The DDR3 one is fully features21:01
openpowerbot[irc] <sadoon[m]1> Featured*21:01
openpowerbot[irc] <lkcl_> you also need to track down a DFI-to-Wishbone or DFI-to-AXI or DFI-to-whatever "Controller"21:01
openpowerbot[irc] <sadoon[m]1> They even ran Linux using it21:01
openpowerbot[irc] <sadoon[m]1> It would at least give us 1GB of real RAM to test with21:02
openpowerbot[irc] <lkcl_> i have removed that task from #961. it wasn't authorized and we have far higher priority tasks to get completed before we can go anywhere near a new NLnet Grant request21:02
openpowerbot[irc] <lkcl_> in one year's time, yes.21:02
openpowerbot[irc] <sadoon[m]1> That sounds good, one year's time yeah21:03
openpowerbot[irc] <lkcl_> one year from now, at least - because there is approx 6 months of *existing* grant work to get done before i am comfortable applying for a new grant21:03
openpowerbot[irc] <sadoon[m]1> Yeah no I do agree there of course21:03
openpowerbot[irc] <lkcl_> at which point from experience it will be about 4-6 months from application to MoU signing21:03
openpowerbot[irc] <lkcl_> and then there is 6 months work21:03
openpowerbot[irc] <lkcl_> so actually about.... estimated.... 14-18 months from now the goal "1 GB of real RAM to test with" is achieved21:04
openpowerbot[irc] <lkcl_> and in the meantime there is HyperRAM which is easy and far less costly.21:04
openpowerbot[irc] <lkcl_> *and* i can persuade NLnet to put it into someone else's *existing* Grant.21:04
openpowerbot[irc] <lkcl_> (to get the higher-capacity HyperRAM PMODs)21:05
openpowerbot[irc] <lkcl_> see how that works?21:05
openpowerbot[irc] <lkcl_> don't let me discourage you from finding things - please make certain to always edit the wiki to include any new PHY/Controller research and/or actual FOSSHW implementations21:08
openpowerbot[irc] <lkcl_>
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openpowerbot[irc] <programmerjake> implementing the ram via another computer idea is likely less expensive than getting custom hyperram boards and shipping them to everyone...21:11
openpowerbot[irc] <sadoon[m]1> lkcl_: Will do21:13
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