VA503+: maximum installable memory? DIMM size limitation?

I'm just wondering, can the 504+ handle more than 256MB of memory? Every
time I've tried (with one 256MB stick and assorted other sticks of PC100 and
PC133 flavors and sizes), the system boots but will not run through memtest
without erroring out. If I run the sticks by themselves memtest runs fine.
Will the 503+ work w/256MB PC100 DIMMs? I've noticed the Tyan s1590 (also
based on the VIA MVp3 chipset) doesn't recommend any DIMMs over 128MB in
size. Is this also true of the 503+? All my 503+ manual states about 256MB
DIMMs is that none were available for testing.

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there is no .sig

The VA-503+ can handle up to 768 MB RAM, consisting of 3 256 MB DIMMs.
The MVP3 chipset can handle a memory density of up to 16 MB per memory
chip. That would mean a 256 MB DIMM must consist of 16 memory chips,
each one containing 16 MB. The 256 MB DIMMs that are more common these
days usually consist of only 8 chips, which will not work because they
consist of 32 MB chips. (In the case of ECC RAM, one extra chip per
side is allowed for the ECC function, so a 256 MB ECC DIMM would have a
total of 18 chips).

Other chipsets from this time period also have the same size
limitations. For example, the Intel 440BX. When these chipsets first
came out, they were designed to handle up to 16 MB/chip, but only 8 MB
chips were available at the time. When the 16 MB chips started coming
out, they worked fine in most of these boards, but some required BIOS
updates to sort out compatability problems.

As for your problems getting the DIMMs to run together, this is often a
result of more memory modules placing more burden on the memory
controller. I do not recall the particulars of the VA-503+ off the top
of my head, but here are some general tips:

Loosen memory timings in BIOS. Set CAS Latency to the highest number,
which would be 3. Also, set the Memory Timings (I forgot the exact
name) more towards "Slow" and away from "Turbo".

If the VA-503+ gives you a way to adjust the memory voltage or I/O
voltage, try bumping it up a notch. The normal DIMM voltage for regular
SDRAM is 3.3 V. Try bumping it up to 3.4 V.

While you are at it, you may check for any BIOS updates in case any
memory issues have been addressed.

By the way, you may hear that the MVP chipset has a maximum *cacheable*
memory size of 255 or 256 MB. Basically, what this means is that if you
put more memory than this in your computer, the overall performance will
actually go down. In practical terms, this means that unless you
actually need more physical RAM than 256 MB, you are better off staying
with 256 MB. On the other hand, if you regular need more than 256 MB,
then you will still benefit from the added RAM, because the it is still
way faster than having your computer access the swapfile on your hard drive.

I hope this helps.

--Alex




Doug wrote:
> I'm just wondering, can the 504+ handle more than 256MB of memory? Every
> time I've tried (with one 256MB stick and assorted other sticks of PC100 and
> PC133 flavors and sizes), the system boots but will not run through memtest
> without erroring out. If I run the sticks by themselves memtest runs fine.
> Will the 503+ work w/256MB PC100 DIMMs? I've noticed the Tyan s1590 (also
> based on the VIA MVp3 chipset) doesn't recommend any DIMMs over 128MB in
> size. Is this also true of the 503+? All my 503+ manual states about 256MB
> DIMMs is that none were available for testing.
>