stiles@MULTI.EE.USU.EDU (G. S. Stiles) (06/21/91)
Does anybody know if it is possible to boot transputers from byte-wide ROMs?? Thanks - Dyke Stiles stiles@cc.usu.edu
csa@SPOCK.BYU.EDU (lyle bingham) (06/22/91)
Yes - See the Transputer Data Book 2nd edition p73 (T805) If BootFromRom is connected high the transputer starts to execute code from the top two bytes in external memory, at address #7FFFFFFE. This location should contain a backward jum should contain a backward jump to a program in ROM. Following this access, BootFromROM may be taken low if required. The processor is in the low priority state, and the W resty and the W register points to MemStart. The above is quoted from the databook It may require some smart circuitry, but it can be done best regards lyle
davidb@brad.inmos.co.uk (David Boreham) (06/25/91)
In article <9106210142.AA05933@multi.ee.usu.edu> stiles@MULTI.EE.USU.EDU (G. S. Stiles) writes: >Does anybody know if it is possible to boot transputers from byte-wide >ROMs?? > Sure, if you have a T225...but I guess that's not your question ? The T4/T8 devices were not designed with byte-wide ROM in mind. However rumours persist of various tricks which can be used to achieve the desired effect. I should add that I have no evidence for any of these ideas ever having been properly tested. We always hang ROMs off T225's or use large amounts where 32-bits is an advantage. 1. Make a demultiplexor which assembles a 32-bit wide word from four ROM accesses. This one gets plenty of mentions but almost certainly costs more than four ROMs, no matter how you do it ! 2. Put the ROM with a state machine, connected to a link adaptor. This works. The SM addresses the ROM and counts up, sending byte-by-byte down the link. You connect the link adaptor to the transputer and boo from link. (Wastes a link). 3. By some devious cunning with the op-codes, you hang an 8-bit ROM on _ONE_ byte of the 32-bit memory interface. Program the ROM with a clever program which only needs one byte to read different data. The rest of the bus can be pulled high/low to fake no-ops or whatever. Never seen this done but heard rumors. You only need a program which copies a bootstrap into RAM and then runs that so we're not talking about anything too complex. This would be neat if it works except for the bus pulling which is going to screw up the loading and cover the board in resistors. (Was that the thing you were mentioning Lyle ?) 4. Order 200,000 parts and we'll put a mask ROM on the chip :) Cheers, David. David Boreham, INMOS Limited | mail(uk): davidb@inmos.co.uk or ukc!inmos!davidb Bristol, England | (us): uunet!inmos.com!davidb +44 454 616616 ex 547 | Internet: davidb@inmos.com
cary@esl.com (Cary Jamison) (06/25/91)
The transputer system I worked on at BYU booted of byte-wide ROMs, so it is possible. However, it was all custom hardware. They had four ROMs sitting side-by-side to get the 32-bit words. I can't tell you much more than that. If you want more information, though, I can supply you with the e-mail address of the professor in charge of the project there. Cary Jamison cary@esl.com