[Techtoolslist] James has been busy!

[Phillip Eaton]

A checksum is a simple addition of all the bytes with the top bits chopped off to
give you a 4 digit hex number e.g. EA46

A signature starts with a seed (e.g. 0000) and each byte is sort of xor'd and
shifted into the seed, to give you a result.

A checksum will miss double errors in different bytes, where they cancel each
other out, whearas a signature (depending on the xor function used to create it)
can be statistically proven to spot certain patterns of errors.

If a signature is right, you're virtually guaranteed the ROM is OK. Checksums are
a bit dodgy by comparion.

Phil 



On Wed Sep 14  9:38 , 'Matt Rossiter' <matt at verio.net> sent:


>By the way, can someone explain the difference between a fluke signature and

>a checksum?  Sometimes my fluke reports a bad rom signature, but that

>doesn't necessarily mean the rom is bad does it?

>

>Matt

>

>-----Original Message-----

>From: techtoolslist-bounces at flippers.com

>[techtoolslist-bounces at flippers.com] On Behalf Of John Robertson

>Sent: Tuesday, September 13, 2005 4:32 PM

>To: Technical Tools Mail List

>Subject: RE: [Techtoolslist] James has been busy!

>

>Let me sell off my 9010A bases before someone makes a PC interface 

>for the pods!

>

>Sigh.

>

>I agree though, that would be best - a number of people have looked 

>into it and said they were going to do it...nothing so far though.

>

>John :-#)#

>

>At 7:25 PM -0400 9/13/05, James Bright wrote:

>>Yeah, that's his name. The source code was there... or mostly there....

>>if I recall. It's not really all that tough to do because the scripts

>>that are delivered to the 9010A are really just keystrokes encoded a

>>specific way. The tedious part is that implementing a parser/syntax

>>checker/compiler and that is really not a whole lot of fun from a

>>programming perspective... BTW, by looking at his code was how I figured

>>out a little bit about "thunking down" to the z80 code.

>>

>>A much more interesting project would be an adapter to control the pods

>>from a PC. Quite a bit of work to get that completed (which is why I've

>>been keeping my eye on some of the Fluke emulation work), but it would

>>open up the possibility of using a more structured language to write

>>scripts. For example, wouldn't it be nice to use a CRC check instead of

>>a Signature check for ROMs... which is a little hard to implement with

>>existing script language.

>>

>>I'll start thinking about what enhancements I can do with

>>tech.quarterarcade.com.

>>

>>JB

>>

>>

>>--James Bright

>>www.QuarterArcade.com

>>Restored Arcade Games for your Home

>>

>>>  -----Original Message-----

>>>  From: techtoolslist-bounces at flippers.com [mailto:techtoolslist-

>>>  bounces at flippers.com] On Behalf Of John Robertson

>>>  Sent: Tuesday, September 13, 2005 2:12 PM

>>>  To: Technical Tools Mail List

>>>  Subject: Re: [Techtoolslist] James has been busy!

>>>

>>>  No, there is another one, written by a Fredric L. Rice that he gave

>>>  to the Fluke community (it's on the FTP somewhere) back in 2002. I

>>>  don't think he included the source code though. I have sent him a

>>>  note to see if he is interested in parting with that - assuming his

>>>  email still works!

>>>

>>>  John :-#)#

>>>

>>>  At 6:50 PM +0100 9/13/05, Martin White wrote:

>>>  >Don't forget that the compiler is just the command line one that

>>>  >came with the 9010a. Therefore proprietry.

>>>  >

>>>  >I think!

>>>  >

>>>  >On 13 Sep 2005, at 18:32, Christopher X. Candreva wrote:

>>>  >

>>>  >>On Tue, 13 Sep 2005, John Robertson wrote:

>>>  >>

>>>  >>>The scripts run on the Fluke 9010A (Z80)...or are you speaking

>>about

>>>  the

>>>  >>>compiler?

>>>  >>>

>>>  >>

>>>  >>I was, sorry.

>>>  >>

>>>  >>

>>>  >>==========================================================

>>>  >>Chris Candreva  -- chris at westnet.com -- (914) 967-7816

>>>  >>WestNet Internet Services of Westchester

>>>  >>http://www.westnet.com/

>>>  >>_________________________

>>>

>>>  _______________________________________________

>>>  Techtoolslist mailing list

>>>  Techtoolslist at flippers.com

>>>  http://seven.pairlist.net/mailman/listinfo/techtoolslist

>>

>>

>>

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