Re: what ho?
On Fri, 7 Mar 1997, Eugene Leitl wrote:
> Anybody noticed TI's new TMS C6x family (at http://www.ti.com )?
> At $96 in large quantities, it's a lot bang for the buck. It's not a
> minimalistic design, but it's there, and it's supported. And 1 MBit
> on-die core plus 1.2 GOPs is a nice thing to have for under $100.
Remember, that F21 could be $1-2 in 25K lots, so $100 buys you a lot of
F21s. Right, Jeff?
The C6x does 8 instruction every 5 ns, and the F21 -- 4 instruction every
22ns (out of SRAM), therefore being only about 8 times slower. Granted,
one needs to buy the SRAM in addition. Can one buy 3x8Kx8 12ns SRAM for
under $11?
On the other hand, executing off DRAM, F21 is only about 20 times slower,
and without the need for SRAM is the clear price/performance leader.
The C6x boasts 2 multiplications per 5ns (not 8). Even at that speed, it
it is not exactly clear how will the data be fed at that rate through the
regular 32-bit interface. Two F21 have 40 bits interface, and four have
80. The memory bandwidth being usually the bottleneck, more often than
not the C6x will spend its time waiting for data, as is the case for the
high-end machines.
Granted, the C6x is impressive with its .25u technology, 250K transistors
and 1Mbit SRAM. On the other hand, the price point is much higher than a
similar price/performance F21, leaving it to high-end applications.
Also, it is not clear whether the memory bandwidth is enough to saturate
the processing power, and in such cases several F21s with wider total bus
might do a better job because of better resource utilization.
Not to mention, that the F21 die is 3/4 empty and I bet that Chuck is
working on putting memory there, which will raise the throughput at least
twice -- to the true 400 MIPs. Jeff, is that right?
--
Penio Penev <Penev@pisa.Rockefeller.edu> 1-212-327-7423
