What could be a complete redesign of a microprocessor if one

G

Gandalf

Guest
I was studying VHDL, when this thought struck me. What features do you think a new microprocessor written in VHDL must possess? If this is the wrong place to ask, kindly redirect me to the relevant group if possible.

-Gandalf
 
On Monday, December 8, 2014 3:54:11 AM UTC+5:30, Dave Higton wrote:
In message <a6f5d2db-2e71-482b-8312-db3426d970ab@googlegroups.com
Gandalf <ankitkulshrestha0912@gmail.com> wrote:

I was studying VHDL, when this thought struck me. What features do you
think a new microprocessor written in VHDL must possess? If this is the
wrong place to ask, kindly redirect me to the relevant group if possible.

Your question makes no sense at all. VHDL is a means to implement
whatever features you wish. It has no limitations that would cause
you to reduce the feature set.

Dave
Click to expand...

Let me rephrase it- If you were to build a microprocessor today which is geared towards microcomputing platforms, what low level feature you would implement in addition to the standard PC,ALU, FPU etc.
 
On Monday, December 8, 2014 3:49:08 AM UTC+5:30, rickman wrote:
On 12/7/2014 1:33 PM, Gandalf wrote:
I was studying VHDL, when this thought struck me. What features do you think a new microprocessor written in VHDL must possess? If this is the wrong place to ask, kindly redirect me to the relevant group if possible.

If you want to know what features to include in a processor design, pick
a processor suitable for the job you want to do and use those. :)

Before you consider rolling your own processor, take a look at the
others out there. There are around 1000 of them so far.

--

Rick
Click to expand...

Hey thanks Rick,
I already went through the MIPS documentation and the ARM documentation. Could you suggest me some more?
 
On 12/7/2014 1:33 PM, Gandalf wrote:
> I was studying VHDL, when this thought struck me. What features do you think a new microprocessor written in VHDL must possess? If this is the wrong place to ask, kindly redirect me to the relevant group if possible.

If you want to know what features to include in a processor design, pick
a processor suitable for the job you want to do and use those. :)

Before you consider rolling your own processor, take a look at the
others out there. There are around 1000 of them so far.

--

Rick
 
In message <a6f5d2db-2e71-482b-8312-db3426d970ab@googlegroups.com>
Gandalf <ankitkulshrestha0912@gmail.com> wrote:

I was studying VHDL, when this thought struck me. What features do you
think a new microprocessor written in VHDL must possess? If this is the
wrong place to ask, kindly redirect me to the relevant group if possible.
Click to expand...

Your question makes no sense at all. VHDL is a means to implement
whatever features you wish. It has no limitations that would cause
you to reduce the feature set.

Dave
 
On 12/7/2014 9:43 PM, Gandalf wrote:
On Monday, December 8, 2014 3:49:08 AM UTC+5:30, rickman wrote:
On 12/7/2014 1:33 PM, Gandalf wrote:
I was studying VHDL, when this thought struck me. What features do you think a new microprocessor written in VHDL must possess? If this is the wrong place to ask, kindly redirect me to the relevant group if possible.

If you want to know what features to include in a processor design, pick
a processor suitable for the job you want to do and use those. :)

Before you consider rolling your own processor, take a look at the
others out there. There are around 1000 of them so far.

--

Rick

Hey thanks Rick,
I already went through the MIPS documentation and the ARM documentation. Could you suggest me some more?
Click to expand...

I meant that home grown CPU designs.

If you are serious about this the question is "why"? I've been down
this path myself designing some number of iterations of MISC type
processors. In the end it was educational, but only moderately useful.
The smallest practical processor I've seen is the picoBlaze from
Xilinx, but it is not HDL, but rather done with Xilinx primitives. So
in that sense my CPU was the smallest I have seen that wasn't also dog
slow, but not by much. There are lots of CPUs of a wide range of sizes
all designed with different goals in mind. The question is, what is
your goal?

--

Rick
 
Hi Gandalf and Rick,

> >>> I was studying VHDL, when this thought struck me. What features do you think a new microprocessor written in VHDL must possess? If this is the wrong place to ask, kindly redirect me to the relevant group if possible.

There are lots of new designs ranging from tiny micros, to DSP/VLIWs, vector processors, embedded multicores etc.

As a shameless plug, you can have a look at my processor, ByoRISC. ByoRISC was conceived some ~8 years ago as a Nios-II or MIPS32 on steroids. Its design is based around cheap, internal, multi-port storage for registers, the kind of one that might be practical in FPGAs (and this depends). It is a scalable design (with full data forwarding from everywhere to everywhere) that can be configured at compile/elaboration-time for a different maximum number of read and write operands for the supported instructions. I was able to use it for at least up to 8 read and 8 write ports. For 8/8, MHz degradation was 15-20% to a RISC-like with 2/1 read/write ports, but overall execution time benefit was around 2.5x-4x for my application set (ByoRISC was better). ByoRISC is a good testbed for exercising custom instructions and stuffing it with additional tightly-coupled functional units.

ByoRISC was also able to sustain better performance than some VLIWs, e.g. the HP Playdoh/VEX that I had used in experiments.

Some readings:
http://www.nkavvadias.com/publications/kavvadias_vlsisoc08.pdf
http://arxiv.org/abs/1403.6632

There was also its sister EDA tool, YARDstick for identifying custom instructions (though not fully integrated into a single flow with ByoRISC development tools):
http://www.nkavvadias.com/yardstick/index.html

The world has moved to embedded multicore of course and ByoRISC might not be too elemental as a brick, but it is a worthy experiment of a scalable ASIP with performance at the 4/8-way VLIW range.


Best regards
Nikolaos Kavvadias
http://www.nkavvadias.com

If you want to know what features to include in a processor design, pick
a processor suitable for the job you want to do and use those. :)

Before you consider rolling your own processor, take a look at the
others out there. There are around 1000 of them so far.

--

Rick

Hey thanks Rick,
I already went through the MIPS documentation and the ARM documentation.. Could you suggest me some more?

I meant that home grown CPU designs.

If you are serious about this the question is "why"? I've been down
this path myself designing some number of iterations of MISC type
processors. In the end it was educational, but only moderately useful.
The smallest practical processor I've seen is the picoBlaze from
Xilinx, but it is not HDL, but rather done with Xilinx primitives. So
in that sense my CPU was the smallest I have seen that wasn't also dog
slow, but not by much. There are lots of CPUs of a wide range of sizes
all designed with different goals in mind. The question is, what is
your goal?

--

Rick
Click to expand...
 
On 08/12/2014 02:42, Gandalf wrote:
On Monday, December 8, 2014 3:54:11 AM UTC+5:30, Dave Higton wrote:
In message <a6f5d2db-2e71-482b-8312-db3426d970ab@googlegroups.com
Gandalf <ankitkulshrestha0912@gmail.com> wrote:

I was studying VHDL, when this thought struck me. What features do you
think a new microprocessor written in VHDL must possess? If this is the
wrong place to ask, kindly redirect me to the relevant group if possible.

Your question makes no sense at all. VHDL is a means to implement
whatever features you wish. It has no limitations that would cause
you to reduce the feature set.

Dave

Let me rephrase it- If you were to build a microprocessor today which is geared towards microcomputing platforms, what low level feature you would implement in addition to the standard PC,ALU, FPU etc.
Click to expand...
The question still doesn't make much sense - the only two valid reasons
I can imagine for developing yet another VHDL processor are:

1) because you want features that you can't get in anything else

2) for research/education

In either case the required features are driving the project.

Michael Kellett
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top