Todd,
You make a good point to all those people out there with older computers
thinking of doing a cheap upgrade.
Generally, ALL socket 7 based PC chipset have fairly low limits on the
amount of cacheable memory (except Intel's 430HX with a 512MB cache limit).
While you can plug in much more memory, the low cache limits severely limit
the extra performance from the extra memory, especially when considering
Windows OS's load from the top of memory down (into the uncached region).
As stated below, Intel FX, VX, and TX have a hard 64MB cache limit. The ALi
Alladin 5 has a 128MB cache limit with 512KB of L2 cache, and 256MB with 1MB
of L2 cache. The SiS 530 has a 64MB limit with 512KB of L2, and 128MB with
1MB of L2. The VIA MVP3 has 128MB with 512KB of L2, and 256MB with 1MB of
L2.
For those that are not so computer savvy, I'll try to explain why L2 memory
cache is so important. Main memory (SIMMs, SDRAMs, etc.) run considerably
slower (10x-50x) than the processor is able to read data. The L1 memory
cache is quite small and sits directly on the processor, while depending on
the processor, the L2 cache is either in the processor die, on the
motherboard, or in the processor as a separate die (SLOT 1 style). This
cache memory is much much faster for the processor to access, with L1
running at full speed compared to the processor, and L2 generally at half
speed or full speed.. When a byte is needed to be read (writing is slightly
different but also affected), the processor first tries to find it in the
cache (L1 then L2). If this fails, then the processor has to sit and wait
many clock cycles for the main memory access. In the worst case, the byte
location needed has been paged to disk, so now it has to wait for the whole
4k page to be read from disk. When all of a region of memory is "uncached"
due to chipset limitations, there is always the performance penalty of
having to read slow main memory. L1 and L2 cache algorithm policies vary,
but generally they work with small blocks of data (~16 to 64 bytes each),
and if a single byte is needed, the whole block is read, though the byte
needed is given to the processor as soon as it is available. Blocks of
memory that are cached and subsequently used often are not replaced when new
memory is needing cached. Memory locations that haven't been accessed much
or recently or both are discarded from the cache and replaced with the new
memory. The algorithms are quite complex and vary, so this is all just
approximate to give some understanding.
So, the situation today is that all the later processors and chipset support
cacheability of at least 512MB. In the case of the Pentium II/III, where
the L2 cache is on the processor, the chipset has nothing to do with
caching, so the processor limitation is 4GB of cacheable memory. The
chipset might impose a limitation of "addressable" memory or 512MB or 768MB,
or something like that, but that is different than cachability limitations.
This is true for Intel's 815e and 815ep chipsets, which has a strict 512MB
addressability limit.
Older Celeron processors don't have an L2 cache, so they are somewhat
performance limited out of the gate, regardless of which chipset they are
attached to. Newer Celerons are coming out with L2 caches, but smaller than
the PII/PIII. Some Pentium III's have smaller L2 caches than the Pentium
IIs, but they run at twice the speed, so the performance is generally
equivalent in the end.
I don't know much about AMD's Thunderbird and Duron processors, but assume
they have followed similarly to Intels cache and addressability limit
increases.
My suggestions are to stick with SLOT1/Socket 370 (intel) or AMD's
processors for new systems for image editing.
[not responsible for typos, I wrote this in a hurry]
Cheers,
Gerald
----- Original Message -----
From: "Todd Stanley" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Monday, February 05, 2001 9:13 AM
Subject: Re: OT: Going semi-digital; advice needed
>
> I think you are confused with the Intel FX, VX, and TX chipsets that were
> around back when Windows 95 was new. With these chipsets the L2 cache
> would not cache the ram over 64MB and that could slow you down (though the
> gains of adding more ram usually made up for the difference plus more). I
> don't see this problem with my computer (VIA chipset, Windows 95, 128MB of
> ram) or any other Win 95 computer with 64+ MB of ram that has a suitable
> chipset.
>
> Todd
>
> At 06:36 AM 2/5/01 -0800, you wrote:
> >It's actualy worse than that while windows 95 will
> >handle 512, preformance for most applications suffers
> >when you use anything over 64. Windows 98/ME will
> >give preformance gains, in general use with 128, but
> >preformance begins to degrade with more memory than
> >that installed. (Graphics software like Photoshop
> >seem to be a special case).
> >
> >--- Todd Stanley <[EMAIL PROTECTED]> wrote:
> >>
> >> Yeah, but operating systems may not be able to
> >> properly handle that much
> >> memory. I don't know the limits but I think 512 is
> >> the limit for Windows
> >> (not NT/2000). It's like hows Windows could only
> >> handle drive partitions
> >> up to 2GB, no matter how large the drive was, until
> >> they came up with FAT32
> >> in Windows 95 OSR2.
> >>
> >> Todd
> >>
> >> At 02:36 PM 2/4/01 -0600, you wrote:
> >> >The amount of memory supported by a PC is a
> >> function of the slots, size of
> >> >each memory simm, and the mother board.
> >> >
> >> >My ABit VL6 supports 768 meg of memory in three
> >> slots. (256*3)
> >> >
> >> >Cy Galley - editor, B-C Contact!
> >> >Bellanca-Champion Club
> >> >Visit us at:
> >> http://www.bellanca-championclub.comAnyone
> >> >
> >> >who knows all the answers...simply doesn't know all
> >> the questions.
> >> >
> >> >
> >> >
> >> >----- Original Message -----
> >> >From: "Aaron Reynolds" <[EMAIL PROTECTED]>
> >> >To: <[EMAIL PROTECTED]>
> >> >Sent: Sunday, February 04, 2001 12:10 PM
> >> >Subject: Re: OT: Going semi-digital; advice needed
> >> >
> >> >
> >> >>
> >> -
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> >>
> >
> >
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