DSP - Architecture Past, Future

DSP  ::  Architecture Past, Future

1. The dinosaurs (70s)
1. Computers only (MIT Lincoln)
2. The first chips (TRW, AMD bit slices, other bit slices)
2. The first steps (79-80)
1. Intel 2920
2. Bell Lab internal
3. DSP of the First Kind (80-95) : A good compromise between application specific and General Purpose (GP)
1. The PSI
2. NEC 7811
3. AMI2811
4. TI 320C10
1. TI C10,C20,C25
5. Motorola 56000
6. And a lot many more
7. ADI enters the fray (21xx)
8. ATT becomes public (16xx)
9. TI starts a revolution every 4 years 
1. FP (89)
2. MP (93)
3. VLIW (97)
10. Motorola weathercock: 24/24 16/24 24/16 16/16
11. ADI "one day I will be bigger"
    
12. ATT "only the professional" 
13. Refer to BDT 1995 for summary
14. Smelling the RISC takeover
15. DSP group "the revenge of the trees"
16. Carmel "the last honest DSP!" 
    
4. DSP of the Second Kind: Back into CPU mainstream (95-05)
1. TriCore
2. ARM9E
3. Hitachi SH
4. Extensions to CPU ISA (ARM, MIPS, PPC, Intel, HP, SUN)
5. TI: from C62 to C66
6.  ZSP, Starcore
7. Blackfin, Tiger Sharc
5. DSP of the Lost Kind? What shall we try now? (05-10)
1. Customized DSP
1. Wireless DSP
2. Customisable DSP
3. Customizable Core: TenSilica, Arc,3-DSP
2. Multi-PE (Processing Elements)
1. Impact of MM architecture
3. MP, MC (Multi channels), MT
4. Re-configurable computing
5. Heterogeneous Platforms
6. Matlab and Custom DSP
7. Is GPU the latest smoking pot? Or is it Cell? 
6. DSP of Any Kind
1. DSP boards
2. DSP custom Chips
3. FPGA platforms
   
7. DSP of the Third Kind (10-20?)
1. Back to the future: Coprocessor seen as a low complexity DSP
1. ASP DSP
2. COP DSP
3. A platform to build the platform: the framework
   
2. Added complexity: Matlab to implementation

Architecture evolution

For simplification sake, we will use the terms archi80 (DSP of the first kind),  archi 90 (DSP of the second kind) and archi 2000 (DSP of the lost kind).

• The typical archi80 is made of 3 blocks (DAU, AGU, PCU ) , buses and memories. These 3 blocks correspond respectively to  the Data Arithmetic Unit, the Address Generation Unit and the Program Control Unit. The terminology matches the architecture previously developed in bit slice designs.To be more precise the architecture was centered on designing datapaths with a microcode memory in the control plane.
• The typical archi90 turns the concept by 90 degrees so that now everything is seen from the  instruction perspective. To that, a new central block is added: the Register File. Hence the 3 afore mentioned blocks became respectively (IP, LS, Fetch/Decode). There is no doubt that archi90 is much more sophisticated than archi80 and allows a solid foundation. But it is also so complex that it needs  a scientific foundation (Computer architecture) and specialized engineers( Architect)...
• When Risc proponents mention the simplicity of the Risc model (as for instance the DLX, MIPS1) they refer to CPU debate of RISC versus CISC (in which they misplaced DSPs). But implementing a DSP with Risc principles is not an average ARM7 design.
• The archi2000 opened new directions in architecture but none of them was a major change. 
• Many new directions (such as multi-core) have very little to do with cores. They are just platform choices. 
• Configurable cores (TenSilica, Arc) boils down to a finer grain way of building a SOC.
• Reconfigurable computing is a real breakthrough since it combines (re)build and run in hardware. Unfortunately it is still in its infancy.
• And so are similar concepts like JIT interpreter (Transmeta) .
• Because of its popularity, the C6x with its VLIW and its 2 cluster datapath is a real breakthrough. But TI is kind of going backward. Firstly their VLIW looks more and more like static SuperScalar and the 2 cluster never expanded into 4,8,16 clusters. Instead they rely on clock speed, multiple multi-level caches and MP for performance. Hardly original...
• All similar attempts (Multi Media CPU) are now dead. 
• For a times there was a revival with the IBM cell and Nvidia GPU but difficult to see the future of DSP when looking at these beasts.
• We had a series of gizmos such as stream processors which petered out like the rest. 
• Now none of these new trends were useless. All will have some impact on future DSP architectures.
• For our purpose our favorite trend are configurable computing. For instance a DSP which includes a Matlab JIT or a DSP which reconfigures its operating units on the fly.
• The archi2010 makes a simple constat
• All effort are now on platform design.
• Software (the lack of it, the price to develop it) is the main killer for a platform
• Developing a new GP core is useless.
• Only customized core can justify the investment. And not even a full core because of the price of developing new tool and software.
• The space remaining for DSP is either coprocessing or a DSP core so simple that the tool development effort is minimal.
• the second case is for simple apps (1K-2K code)

REFERENCES -Found in the garage - Filed under DSP 

1. Floating Point DSP

REFERENCES -Found in the garage - Filed under CPU

1. MultiMedia MM CPU
2. DLX