> On Tuesday, April 9, 2002, at 02:31 AM, Xandr wrote:
>
> > Hello, I recently obtained an older 840 quadra and was upgrade the ram
> > and
> > noticed in the process on the Mother Board four addition slots similar
> > to
> > the ram slots towards the center of the board, can someone help me
> > identify
> > what these slots are for. They were empty.
>
> These are for additional Video RAM, you can put 4 256kb VRAM SIMMs in
> here to bump it up to 2MB. I have 2MB in mine and it is pretty cool :).
> The best thing is that 256MB VRAM is dirt cheap and very common because
> people who break LCs and Quadras have tons of the little blighters from
> earlier machines, there 1 in every LC or LCII for example. You can not
> use 512kb SIMMs as the upper 256kb of each SIMM is ignored. AFAIK they
> must be in pairs.
[...]
You have to install them all 4 at a time. According to Apple, they have to
be 80 nanoseconds, & the VRAM SIMMs in the IIvx & LCs with 020/030 CPUs were
100ns, stock.
But I have found that some 100 ns 1s worked just fine in a Quadra 650.
Probably they were a bit over-engineered, seeing as they were Apple-branded
(w/ Toshiba chips) -- Apple's are usually labelled "4*8" VRAM, as that was
the original use, to upgrade an Apple 4*8 nubus card to an 8*24.
I'm not sure as I can say the same about all 3rd-party VRAM, so it's
probably best to ask for 80 ns VRAM, whatever you get.
You can use 512k SIMMs, but, as Mark says, only the bottom half of each chip
will be used, & since 512k-ers are considerably less abundant & cheap than
the 256k-ers, don't bother buying them, unless you somehow get a *really*
good deal (like free).
--
Over,
Jutso
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