TI MSP430
in [Embedded]
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From: CBFalconer on 10 Apr 2006 08:53 Mark Borgerson wrote: > In article <4438F445.5EF07B7D(a)yahoo.com>, cbfalconer(a)yahoo.com says... >> larwe wrote: >>> Gary Reichlinger wrote: >>> >>>>> basis of its similarity to the PDP-11(1). >>>> >>>> Do you guys belong to AARP? >>> >>> Not yet, but the curmudgeonliness flux density is high in the >>> engineering field, so it's forgivable that you would ask the >>> question :) >> >> What we really need is a PDP-8 on a chip. >> > "He who does not study is doomed to repeat it." > (couldn't track down the author). > > Intersil 6100. IIRC that was three chips :-) PMOS at 12 V ? -- "If you want to post a followup via groups.google.com, don't use the broken "Reply" link at the bottom of the article. Click on "show options" at the top of the article, then click on the "Reply" at the bottom of the article headers." - Keith Thompson More details at: <http://cfaj.freeshell.org/google/> Also see <http://www.safalra.com/special/googlegroupsreply/>
From: Roberto Waltman on 10 Apr 2006 17:17 CBFalconer <cbfalconer(a)yahoo.com> wrote: >>> What we really need is a PDP-8 on a chip. >> Intersil 6100. >IIRC that was three chips :-) PMOS at 12 V ? No, the 6100 and its successor, the 6120, were one chip implementations of the PDP-8. The FAQ is here, http://www.cs.uu.nl/wais/html/na-dir/dec-faq/pdp8.html And a modern PDP-8 can be found here, http://www.sparetimegizmos.com/Hardware/SBC6120-2.htm
From: Jonathan Kirwan on 10 Apr 2006 17:53 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
From: Jim Granville on 10 Apr 2006 19:25 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. That's pretty much true for any uC you choose to analyse. There are always things they "could have done better", or areas where a core has been pushed into applications the original design brief did not cover. The best cores are those designed to be microcontrollers from the ground up. Remember the MSP430 is quite old, and so the silicon yeild and design cost of 'just another mode' will have been quite high. It was more important for them to meet targets in die area and price, and ROM is one of the cheapest areas in a die design. Assembler will have dominated. Still, if there are large savings to be made with your changes, then perhaps a Soft-CPU for FPGA would be one way to actually implement them ? - then you have a delay in Software support, as it catches up to the new features. -jg
From: Clifford Heath on 11 Apr 2006 08:54
SMS wrote: > You can buy the development tool (USB > stick) for 1/2 price ($10), with the coupon code MS681LXD. Ok, I give up. Where do I enter the coupon code? ti-estore is happy to let me order at $20, but $10? |