Subject: Re: Mips Chips from NEC

From: Andreas Busse <[email-masked]>
Date: Thu, 29 Jul 93 16:51:03 +0200

> Any reason the R4200 is being compared to the SC chips and not the PC?
> Based on pin count alone I'd expect the PC at 179 pins to be a fair 
> amount cheaper then the SC at 447 pins.  Or is the 4200 a SC??

I don't know. So far I know is the R4200 a PC version.
It's *very* difficult to get informations about the R4200.
An engineer at NEC asked "no problem, how many do you want to buy ?"
while a distributor told me that he had never heard about that part
and that NEC doesn't produce it !
Seems we are a bit ahead of the technology...

However, I've got a data sheet for the NEC VRX / uPD30450. It looks
like that this is what we call the R4200. At least the detail that
this CPU has a 5-stage pipeline instead of the 8-stage pipeline used
in the R4000 and R4400 makes it very probably that it is the R4200.

Some Specs quoted from the sheet (Feb. 93):

Input Clock: 		40 MHz
Operating Clock:	80 MHz
I-Cache:		16 kB
D-Cache:		 8 kB
Power Consumption:	 2 W

System interface compatibel with the Vr4000 series.
Instruction set compatibel with the Vr4000 series.

So far, so good. But there's one important thing, probably a great
disadvantage for some of the group: The VRX has ***NO*** FPU !!!

Again, qouted from the data sheet:

All floating point instructions, as defined in the MIPS ISA for
the floating-point coprocessor CP1, are processed by the same
hardware as for the integer instructions. That is to say, there
is no separate floating point coprocessor. However, the execution
of floating point instructions can still be disabled via the
coprocessor usability CU bit defined in the CP0 status register.
[end of qouted material]

Here are some examples of floating point instruction timings:
(in pipeline clock cycles)

Insn		S	D
--------------------------
Add.fmt		3	3
Sub.fmt		3	3
Mul.fmt		11	20
Div.fmt		28	57
Sqrt.fmt	28	57
Abs.fmt		1	1
[...]
S=single prec., D=double prec.

So far I understand the data sheet, these instructions
are executed in parallel to loads, stores and so on.
The CPU stalls when, for example, an int-multiply is
in progress and a second multiply, no matter what format,
is to be executed.
I would say, except of Mul and Div, this is the same
timing as the R4000 and R4400 have. I can't decide
if the performance of Mul and Div satisfies the requirements
of the group. All I can say is: It's ok for *me*.

Any comments ? Please - if we really want to make hardware
instead of vapor-ware, wakeup, guys. Here's something to discuss.

Cheers,
Andy

-------------------------------------------------------------------------------
        Waldorf Electronics GmbH        | Phone:  +49 (0)2636-80294
              R&D Department            | Fax:    +49 (0)2636-80188
Neustrasse 9-12, 53498 Waldorf, Germany | email:  [email-masked]
-------------------------------------------------------------------------------

---

From: Amos Shapira <[email-masked]>
Date: Thu, 29 Jul 1993 18:32:14 +0300

In message <[email-masked]> Andreas Busse writes:

 [ lots of info,  bottom line is that the R4200 doesn't have a FPU ]

|Any comments ? Please - if we really want to make hardware
|instead of vapor-ware, wakeup, guys. Here's something to discuss.

Ok,  so shall we take a vote or what?

I am not a hardware type but the R4200 seems to be enough for me it and it
eats 486/66 raw even as it is (here is the table again:

Vendor          Clock   Chip    Price   SPECint92       SPECfp92
unspecified     100     R4000SC 640     61.7            63.4
unspecified     150     R4400SC 1120    88(est)         97(est)
NEC             80      R4200   70      55              30
                                                        ^^
And, for comparison
Intel           66      486     542     32.2            16.1
                                                        ^^^^
Intel           66      Pentium 965     64.5            56.9
)

and the Pentium is out of the question price-wise as far as I'm concerned,
not to mention that going for it must mean waiting for another year at least.

Especially when you take the price/performance and at what price do we want
the system to end up with, I vote for the R4200 and let's go on with the rest
of the design.

Only one question (not that it is going to change my view): you mention
a possibility of a separate FPU.  Is it possible to leave space for a socket
for it a-la the 386/387 combo?  (again,  I'm not a hardware type so please
bear with me if this is a stupid question).

I hope I'm doing the right thing but I propose that others on the list who
kept quite so far (like me) and followed the discussion for the last couple
of weeks will let us all know what they think (is there an echo out here ? :).

Maybe the "core" of this list should appruve of this before things get out
of hand, ok?

|
|Cheers,
|Andy
|
|------------------------------------------------------------------------------
|-
|        Waldorf Electronics GmbH        | Phone:  +49 (0)2636-80294
|              R&D Department            | Fax:    +49 (0)2636-80188
|Neustrasse 9-12, 53498 Waldorf, Germany | email:  [email-masked]
|------------------------------------------------------------------------------
|-

Bye,

--Amos

--Amos Shapira (Jumper Extraordinaire) |  "It is true that power corrupts,
C.S. System Group, Hebrew University,  |   but absolute power is better!"
Jerusalem 91904, ISRAEL                |
[email-masked]                    |          -- the Demon to his son

---

From: Bill Broadley <[email-masked]>
Date: Thu, 29 Jul 1993 11:35:45 -0500 (EDT)

> disadvantage for some of the group: The VRX has ***NO*** FPU !!!

As far as I'm concerned we shouldn't worry about implementation as
much as the benchmarks.   Whatever has the best price performance
sounds good to me.  Although the fact that a 4000 can be upgraded
to a 4400 sounds like a good advantage to me.

The 4200 is around 55/30 specint/specfp
    4000 is around 62/63
    4400 is around 94/105
    601 is around 50/80

Of the chips we have prices for (4[04]00SC and 4200) the 4200 sounds the most
attractive, but (PC) prices may make the 4000 much more attractive.

I think another critical issue is whether we go with the ARC 100/150 
manufacturing kits.  If we do we can do 50 Mhz or higher, and have to use the 
mips chip.

Powerpc seems to be in the running as far as price/performance and
running gcc+gas is concerned.

> instead of vapor-ware, wakeup, guys. Here's something to discuss.

The cost difference between a 4000PC and the 4200 is the only thing I need
to decide.

-- 
Bill					1st>	[email-masked]
[email-masked] <2nd 	3rd> 	             [email-masked]
Linux is great.         Bike to live, live to bike.                      PGP-ok