SPU

spu_insert is used to put a scalar value into a specific element of a vector.

spu_rlmaskqw operates on the whole quadword at a time, but only up to 7 bits (it performs a modulus on count to put it in the proper range).

While it would be relatively easy to create a new GDB target for the SPU itself, most users need to debug interaction between PPE and SPE.

This SPU context is treated like a physical SPU, and the current implementation enforces a direct mapping between them.

When the SPU needs to do any standard library calls like printf or exit, it has to call back to the main thread.

The concurrent nature of the processing and data transfer is what gives two-stage pipelining its edge in SPE programming.

The two transmission steps do not involve the SPU at all, but only the MFC (which is part of the larger SPE).

The main communication method of the SPU with other parts of the Cell processor is defined by a number of "channels. "

An SPU uses vector operations itself and can thereby execute up to eight floating point instructions per clock cycle.

It has three mailbox registers for each SPU, and each of those accesses one of the three SPU mailbox channels.

Both of these can be easily avoided by careful selection of SPU intrinsics and good data structure design.

spu_extract pulls out a specific element from a vector and returns it as a scalar.

In this program, since the problem is trivially parallelizable, you can actually have as many buffers as the SPU's local store can support.

The suction tray SPU used for sucking the work pieces with the lubricity appearance.

When an SPU tries to read from an empty mailbox, it will stop execution until some value is written to its memory-mapped register.

Since the SPU instruction set is not directly related to an existing CPU architecture, a new back end was written for both GCC and binutils.

It turns out that several SPU instructions deal with only one of the register's values.

The SPU has no real hardware support for branch hinting.

The SPU intrinsics allow programs to freely switch among high- and low-level code, but all within the semantic framework of the C language.

The SPU actually loads two instructions at a time from a doubleword-aligned boundary.

In the code written so far, the SPU has simply waited for the MFC to finish before processing anything else.

To call a function according to the SPU ABI, all you need to do is put the parameters into registers, and then call brsl $lr, function_name.

An SPU resembles a cross between a simple CPU design and a digital signal processor.

The SPU is built to deal with data in batches, so moving to a buffer-at-a-time model will make the enhancements easier.

When the PPE writes a data word to that address, the SPU can read from its corresponding mailbox read channels.

mbox and ibox are used to read data written to the SPU mailbox write channels and have slightly different semantics.

spu_rl rotates each element of val left by the number of bits specified in the corresponding element of count.

This is critical, as the SPU can only load exactly 16 bytes at a time, aligned to exactly a 16-byte boundary.

spu_splats works like spu_promote, except that it copies the value to all elements of the vector.

SPU processes can be scheduled by the kernel, and all users can create them without interfering with each other.

This makes it possible to replace physical SPUs as the underlying unit of the abstraction from processes running on the SPU.

The SPU intrinsics documentation (see Resources) defines simplified vector type names starting with vec_.

Normally, no relocations need to be applied, since SPU programs are statically linked.

spu_eqv is a bitwise equivalency operation, not a per-element equivalency operation.

An MFC can have multiple concurrent DMA requests to one address space outstanding from both the PPE and the SPU.

Some of the common sources of exceptions are not even possible on the SPU.

spu_mul handles floating point multiplication (single and double precision).

Other challenges are the integration of SPU program execution into existing tools like GDB or OProfile.

However, with the SPU, the results are stored in a general-purpose register -- register 4 in this case.

The memory-mapped registers are used by the PPE to control certain aspects of an SPE, but are not accessible by the SPU code itself.

The SPU queues a DMA GET to pull a portion of the problem data set from main memory to a buffer.

Remember that the SPU registers are 128 bits wide, but our value is only 32 bits long.

Now, the integer multiply instructions on the SPU are somewhat problematic, especially signed multiplication (using the mpy instruction).

The SPU instruction clz (count leading zeroes, called spu_cntlz in the C language intrinsics) is perfect for this.

A different approach to using SPUs is to define a set of system calls.

Also, exceptions resulting from executed code aren't reported to the SPU itself.

Future articles examine SPU programs more in depth, but here's a quick rundown of what is happening.

This requires changes to the OProfile kernel code to sample the SPU instruction pointers regularly.

For addition, spu_add, when given two vector unsigned ints as parameters, will generate the a (32-bit add) instruction.

The solution the LTC team finally chose is to create a virtual file system to externalize the SPUs.

Using spu_mfcstat allows you to both check on the status of DMA requests and wait for them.

As in assembly language, spu_sel looks at each bit in conditional.

Instead of providing an abstraction of logical SPUs, this interface is thread-oriented and behaves in a similar way to the pthread library.

When an SPU thread gets created, the library will create a new thread that manages the SPU context asynchronous to the main thread.

The SPU queues a DMA PUT to transmit the buffer back to main memory.

Previous discussions about the SPU have focused on the SPU's assembly language to help you get to know the processor intimately.

SPU code is compiled separately from the PPC code and gets loaded at run time.

Curing properties of SPU sealant were studied.

When this happens, the SPU is stopped and the ioctl call is interrupted.

Now, there are two compilers currently available for SPU programming, and, as one might expect, they excel in different areas.

A signal might need to be delivered to a thread that is executing SPU code.

If you need to convert between types, use an appropriate SPU intrinsic.

spu_cmpgt performs a greater-than comparison while spu_cmpeq performs an equality comparison.

Before you start to run CPC, you need to find a small SPU application named "simple" in Cell SDK.

spu_rlmaskqwbyte works similarly, except that count is the number of bytes instead of bits, and count is modulus 16 instead of 8.

spu_splats((unsigned int)5) creates a vector of unsigned ints with each element having the value 5.

wbox is used to write into the SPU mailbox read channel.

Instead, the SPU can access any 128-bit word in the local store at L1 cache speed.

The SPU has 128 general-purpose registers, each 128 bits wide.

The best way to store it is as a tag mask so that it can be used directly as your mask for spu_mfcstat.

If a serious error occurs, for example, an invalid opcode, the SPU is stopped and an interrupt is delivered to the PPE.

spu_insert(5, myvec, 0) returns a copy of the vector myvec with the first element (element 0) of the new vector set to 5.

Research and Property Test of Starch Reducing Viscosity Agent SPU

A private memory area within the SPU called the local store (the size of this area on the PS3 is 256K)

Here are some of the more common SPU intrinsics (types are not given as most of them are polymorphic)

Here is the PPU code to make use of the SPU code (enter as ppu_dma_main. c)

Look at one iteration in the loop and see how it performs in the SPU pipeline. I've added no-ops so you can see the pipeline issues better