Re: Star Wars mathbox math

Hi,

>From the man who designed the mathbox is an explanation of how 4000 hex
represents 1.000, so 1.000 x 1.000 = 1.000

http://www.jmargolin.com/uvmath/uvmath.htm#What Is

I've looked at the mathbox myself, it's clever stuff:

http://www.wardclan.f9.co.uk/Star%20Wars%20Mathbox.html

Hope that helps.

> PPS. Setting bit 8 of the instruction PROMs loads the accumulator, but
> what does it mean to set bit 9 and 'Road' the accumulator?

It's a typo!! Should be "Read Accumulator" If you look at the schematics
'Instruction Strobe Gates' you can see that IP9 produces 'READACC' signal,
which enables Accumulator outputs and writes to Math RAM.

Good luck fixing your board!

Regards,
Neil

----- Original Message -----
From: "Douglas Gauck" <douglas@gauck.com>
To: <vectorlist@vectorlist.org>
Sent: Thursday, September 26, 2013 6:40 AM
Subject: VECTOR: Star Wars mathbox math

> Working on two SW main boards that complain about bad RAM at 5F and 5H
> even when replaced with known good chips. I think it's elsewhere as they
> also fail four of the six matrix tests (15, 16, 18 and 20), all the
> divider tests, and tests A, B, C and D. I would love to know how the math
> works as shown in the SP-225 Troubleshooting Guide for example:
>
> test 17 (passes) performs (5555-0000) x 4000 = 5555
>
> test 18 (fails) performs (0000-5555) x 0000 = 5555 if you go by the test
> or (0000-5555) x C000 if you go by the first diagram on page 12
>
> test 19 (passes) performs (2AAA-0000) x 4000 = 2AAA
>
> test 20 (fails) performs (0000-2AAA) x C000 = 2AAA
>
> test C performs ACC = (1B2C-0000) x 4000 + (196A-0000) x 4000 whose result
> should be 3496
>
> test D performs ACC = (2696-1B2C) x 4000 whose result should be 0B6A
>
> I understand binary and hex but neither is helping me understand how any
> of the above operations could calculate the way the guide says they do.
>
> Can anyone explain this?
>
> -Douglas
>
> PS. seems my Accumulator seems to hold onto the first value it gets, which
> is why 17 and 19 pass but 18 and 20 fail with 0000, A with 0001, C with
> 196A and D with 2696 which is interesting. Test 15 and 16 fail with 1B2C
> which I can't explain and B ends with 0000.
>
> PPS. Setting bit 8 of the instruction PROMs loads the accumulator, but
> what does it mean to set bit 9 and 'Road' the accumulator?
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Received on Thu Sep 26 18:21:44 2013