[J-core] Synthesis for Silicon?

D. Jeff Dionne jeff at SE-Instruments.com
Tue Sep 10 22:02:00 EDT 2019

On Sep 10, 2019, at 5:43, Joh-Tob Schäg <johtobsch at gmail.com> wrote:

>>> Can you tell me and the community more about this?
>> J2 was designed for a mixed signal grid monitor chip, on a TSMC 152nm process.  It came in at about 40k gates, and about 0.45mm^2 in this process.
> This is just the J2 or including the DSP?

This is just the J2 CPU core, not an SoC.

> Any estimates for the J1 already?

Probably around 15-18k gates.

>>> How expensive are the fixed and per chip costs?
>> Depends on if it's a multi project wafer or a full mask set.  180nm full mask set is about $100k US.
> I have no idea what the difference between multi project wafer or a full mask set is. Can someone explain?
A MPW, also called a shuttle run, is a shared wafer.  The mask sets, that is tooling, and wafer cost, is shared between us and a bunch of other (unrelated) customers.  A full mask set is the up front tooling to produce full wafers full of chips.

>>> What clock rates are possible at the targeted node?
>> We're still optimizing.  We can for sure hit 125MHz in 180nm, and probably 500MHz in 45nm.
> Mhh i looked at some processors i could find at the same node.
> Wikipedia mentions
> - the PowerPC 7455 “Apollo 6” was produced with Motorola's 0.18 µm
> (180 nm) HiPerMOS and it is said to clock >1GHz.
> - the second generation Athlon, the Thunderbird, clocked between 600
> MHz to 1.4 GHz and was made using 180nm
> - the Celeron Willamette was clocked at 1.7 GHz also produced at 180nm
> - the PS2 emotion engine at 294 MHz being a vector processor

These are all so called ‘full custom’ layouts, not synthesizable soft cores.  A good comparison is ARM M4, where we are roughly equivalent in equivalent process.

> For 45nm i could find several x86 chips in the 2~3GHz, a PowerPC at
> 1.243 GHz and for ARM the OMAP4 at 1.2 and a Samsung Exynos 3110 at
> 1.0~1.2 GHz. There was also an outlier the z196 which clocked up to
> 5.2 GHz

We are closer here.  J2 is a 5 stage pipeline.  These are significantly deeper, and therefore the clock speed is faster… each stage is simpler.

> Why is J-Core clocked so much slower at the same node size than
> commercial chips which eyed for performance or performance per Watt?
> Is it in the ISA or just in your design which does not prioritize performance?

It’s not the ISA, it’s the choice of implementation methodology.  Squeezing 1GHz out of 180nm is just not necessary (or done) anymore.  We are not slower than other soft cores, synthesized to standard cell.  The ISA does make a difference though, we perform better at a given clock speed.

>> Not right now, no.  The chip SEI was doing was about 1 to 2W power budget.  But it had 16 DSP cores and 32 hardware accelerators for power system measurements, and 6 high speed LVDS SERDES.
> Are looking into releasing the DSP design too?
> Will it under the J-Core name too?

Yes.  It is tentatively called S-Core DSP.  It’s a very traditional DSP, and so the audience is slightly different.  The design is 2 stage, 5 way issue, 18bit, X Y P Harvard memory space design, with 4 way multithreading… which is necessarily a bear to program.  But if you need to to signal processing on chip, it’s really something :)

>> Cheers.  A little vague, but we're getting there.
> Any details get the community excited. It is probably good that not all information is released at once any way.

Not meaning to drip it out… we’re just running flat out on making things happen, technical and non technical :)

> Cheers Johann-Tobias

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