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Re: Larger memory option for VAXstations

On 2015-08-19 14:50, Felix Deichmann wrote:
2015-08-19 14:29 GMT+02:00 Johnny Billquist <bqt%update.uu.se@localhost>:
That don't make sense. 36 x 4mx1 would mean 32 megs of memory. My VX4000/90
have 128M of memory, and that was DEC original. So obviously DEC also made
16Mx1 based memory modules.

Pardon, but 36 x 4Mx1 means 16 MB of usable memory (considering
parity, i. e. 9 bit per byte).

Yeah, I was also assuming parity on each byte.

36 x 4Mx1 = 150994944 bits, and 150994944 bits / (9 bit / byte) = 16
MB. Or am I completely wrong now?

You are right. I don't know how I managed to count to 32M. Sorry.

And your VS4000/90 has the max. 128 MB from using 8 DEC original
modules with 16 MB each, right? At least my /96 is configured that
I thought that for the VS4000, the 16 MB module was the largest
original one available.

I think so too. And to correct the math, the 128M means that they must be using 32Mx1.

For 512 meg, why not locate 64Mx1 memory chips? Or did those not exist?

Might be even rarer than 4Mx1 or 16Mx1. And maybe the larger (and
therefore later) ones are only available as EDO, which could introduce
new trouble when the machine expects "plain" DRAM and its timing.
Don't know.

Well, correcting my math. If we want 512MB with 36 chips means that each chip needs to be 128Mx1.

But this whole idea will require serious effort, fiddling and money...
Why not just buy a MicroVAX 3100/88 or /98, which is NVAX and seems to
support 512 MB by design? :)

The CPU do, but does the motherboard? That was what Nemonix was replacing...


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