TI MSP430
in [Embedded]
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From: John Perry on 11 Apr 2006 22:32 Gene S. Berkowitz wrote: .... >>The coupon expires on April 15th, so hurry. > > > ..but be aware that it's severely backordered. > I placed my order (full price) on 25-February; I'm still waiting... > Well, they just told me in the verification email that it was to be shipped at the end of April. Here's hoping... John Perry
From: DJ Delorie on 11 Apr 2006 23:25 John Perry <jp(a)no.spam> writes: > Well, they just told me in the verification email that it was to be > shipped at the end of April. Did they say *which* April?
From: John Perry on 11 Apr 2006 23:47 DJ Delorie wrote: > John Perry <jp(a)no.spam> writes: > >>Well, they just told me in the verification email that it was to be >>shipped at the end of April. > > > Did they say *which* April? :-) jp
From: Jonathan Kirwan on 12 Apr 2006 00:22 On Tue, 11 Apr 2006 21:39:27 -0400, Gene S. Berkowitz <first.last(a)comcast.net> wrote: >> The coupon expires on April 15th, so hurry. > >..but be aware that it's severely backordered. >I placed my order (full price) on 25-February; I'm still waiting... I ordered some in mid-February, as well. Received the two on March 13th. I've got a _bunch_ more on order, though. Just placed last week. We'll see. Jon
From: David Brown on 12 Apr 2006 05:39
Jonathan Kirwan wrote: > On 10 Apr 2006 09:13:11 +0100, David Brown > <david(a)westcontrol.removethisbit.com> wrote: > >> Jonathan Kirwan wrote: >>> On Sun, 09 Apr 2006 00:16:04 GMT, Marc Ramsey <marc(a)ranlog.comREMOVE> >>> wrote: >>> >>>> larwe wrote: >>>>> MSP430 is a truly elegant architecture, there's no denying it. von >>>>> Neumann simplicity, totally transparent handling of registers and >>>>> addressing modes; I really can't find much to fault with it (except >>>>> maybe the way info memory is handled). But: >>>> Of course, the architecture is a simplified version of the TMS9900 CPU, >>>> which was derived from the TI 990 minicomputer, which was in turn a >>>> rip-off of the PDP-11 ISA, with slight changes (fewer addressing modes, >>>> allowing twice as many registers) to avoid patent issues... >>> I have a few comments about a pdp-11 comparison at: >>> >>> http://users.easystreet.com/jkirwan/new/msp430.html >>> >>> Jon >> Your comments are (as far as I can tell) factually correct, but the >> reaction that springs to mind is "so what?". > > hehe. No problem. > >> As an embedded programmer, >> I really do not care how a particular embedded micro compares to an old >> minicomputer cpu (other than for historic interest, of course - in which >> case it definitely is interesting). And as for possibly misleading >> marketing from TI - it's not exactly new or unusual! > > I did point that out but that wasn't the point, which it appears I > didn't communicate well enough on the page. My fault. > >> What is much more relevant is whether the register set and addressing >> modes of the msp430 really are appropriate for their target >> applications, or whether they would have been better off with the PDP-11 >> arrangement. I'm far from convinced - certainly, the example you gave >> (PC-relative CALL) is obscure indeed, and I think the benefit of more >> registers well outweighs this missing feature. > > I completely disagree. There is no question in my mind that the price > paid was too high -- for embedded applications, I mean. > >> One thing that is definitely missed, however, is all four addressing >> modes as the destination for two-operand instructions. At the very >> least, there should have been a hack in the MOV instruction to allow @Rn >> and @Rn+ modes in the destination. > > The destination side is terrible. And it leads to expanded code size > as well as slower execution on normal and common tasks. I've looked > at weighing various algorithms (I write a LOT of assembly code, in my > practice) which I've hand-written both for the existing MSP-430 as > well as a hypothetical MSP-430 which was closer in instruction design > to the PDP-11 and it's almost always the case that the PDP-11 > arrangement pays off in spades. > > They made the wrong choice. IMHO, of course. > >> As for the missing PDP-11 addressing modes, they are not such a great >> loss. The indirect modes are almost entirely superfluous when you have >> enough registers to hold pointers in registers, rather than having to >> have them in memory or on the stack. It's not often that pointers to >> pointers turn up, at least not in embedded programming. Auto-decrement >> modes are nice, but how often are they used in practice? *(p++) far >> outweighs *(--p), as long as you have a stack pointer and push/pop >> instructions. Perhaps it would be a useful mode for MOV, but not otherwise. >> >> So if you want to say that the msp430 is not as close to the PDP-11 as >> TI marketing seems to think, then I fully agree. But if you think >> that's a bad thing, then I disagree. > > Well, I use the MSP-430 and like it. It's just sad to see how badly > an early choice demolished what might have been. Especially, because > it wouldn't have required the invention of anything new at all and > also because there is ample code experience which, in my opinion, > argues very well against this choice. The additional advantages of > having extra registers is more than offset by the damage caused by > loss of addressing modes. The reduction in memory spills doesn't pay > for itself. > > Jon I agree entirely on the issue of the destination addressing modes (especially for MOV - it's not nearly as important for other instructions). As for the other differences, I'm not convinced (although the fact that *you* are convinced is an influence). I'd have to look at it in a lot more detail some time. The trouble is, 16 bits is not quite enough to make a good instruction set, at least not with 16 registers. With 18 bits, you could get the best of both worlds. Of course, that leads to complications during program updates, and could cause marketing folks to lose their tenuous grip on reality (like Microchip's "14-bit microcontroller"). |