Date : Sat, 24 Nov 2012 14:27:24 -0000
From : rgcolem.myorg@... (Rob Coleman)
Subject: Upgrading a 32016 co-processor to 10MHz
On 24/11/2012 9:40 AM, Rob Coleman wrote:
> On 24/11/2012 12:43 AM, Jules Richardson wrote:
> > I don't have my notes handy, but I think there's a jumper you'll need to
> > fit in order to insert a wait state when doing RAM access; a 150ns cycle
> > time equates to 6.67MHz, so is fast enough to do one access per clock
> > cycle
> > at 6MHz, but not at 8 or 10.
>
> Could this be the LK7? Looking at the schematic from John K.'s site, it
> chooses which output of a LS393 binary counter to use for ram refresh.
Looking at this more closely, the ACW Service Manual mentions link MLW1A:
MLW1A Wait state on all RAM cycles [Link if Xtal is > 16Mhz]
This would seem to map to LK3 on the co-pro as the affected signal is on pin
21 of the TCU. From my reading of the circuit diagram, making the BW1 link
to PW1 looks like having the same effect as making MLW1A on the ACW.
Fitting the link certainly slows things down, at least in a simple BAS32
test:
10START=TIME
20 FOR I%=0 TO 10000:NEXT
30 PRINT TIME - START
gives:
6MHz (no link) 93
8MHz (no link) 70
10MHz (with link) 63
10MHz (no link) 56
Thanks again for all the help,
Rob
-----Original Message-----
From: Rob Coleman
Sent: Saturday, November 24, 2012 9:40 AM
To: bbc-micro@...
Subject: Re: [BBC-Micro] Upgrading a 32016 co-processor to 10MHz
On 24/11/2012 12:43 AM, Jules Richardson wrote:
> I don't have my notes handy, but I think there's a jumper you'll need to
> fit in order to insert a wait state when doing RAM access; a 150ns cycle
> time equates to 6.67MHz, so is fast enough to do one access per clock
> cycle
> at 6MHz, but not at 8 or 10.
Could this be the LK7? Looking at the schematic from John K.'s site, it
chooses which output of a LS393 binary counter to use for ram refresh.
However, pictures and schematics for the ACW show this in the 'B' position
which is the same as in my 6MHz 32016. I may just try it as is to see how
stable it is at 10MHz - I've found a cheap supplier of suitable 100ns ram
but don't fancy the idea of removing 32 ram chips!
Thanks to everyone for all the helpful suggestions.
Rob
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