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First post, by reodraca

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As I understand it, early Intel-branded Pentium chipsets (or at least a couple of them) had a maximum cachable memory amount of 64 MB. Did the VLSI SuperCore 590 chipset (82c591/592/593) have any such limitations? I can find next to nothing about this chipset in terms of information.

I am considering upgrading my AT&T Globalyst 620 (which has the aforementioned SuperCore) to its maximum of 192 MB for s***s and giggles, but was wondering if I'd see any major decrease in performance past 64 MB. It already has the 256k COASt it came with and I upgraded it to a 133 MHz processor, but I want to see what this thing can do when maxed out to its limits, aside from soldering in a VRM in order to use an MMX chip (which I find unnecessary for this system) and overclocking (something I don't generally do).

Thanks in advance, Vogons community!

Reply 1 of 14, by Horun

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Depends on the TAG ram size. https://theretroweb.com/chipsets/578#VL82C591
You can check the manuals of other boards with same cache controller: https://theretroweb.com/motherboards/?chipset … 78&showImages=1

Hate posting a reply and then have to edit it because it made no sense 😁 First computer was an IBM 3270 workstation with CGA monitor. https://archive.org/details/@horun

Reply 2 of 14, by dionb

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Actually the early Intel Pentium chipsets had much higher cacheable limits - i430NX could cache 512MB of RAM. It was only after Pentium moved into the mid/low-end with i430FX in 1995 that Intel cost-cut that to 64MB max.

As for the VLSI 590 - it seems to be the same as with the i430HX: with one tag it's limited to 64MB, with a second tag it can go up to 512MB.

If unsure about your board, install >64MB and run the CTCM tool (not to be confused with the Creative utility of same name). It should tell you how much of your RAM is cacheable.

Be aware that more RAM than your programs need never increases performance (at least not with vintage PC OSs), so as a rule it's fastest to stay under cacheable limits unless you're very sure you need more RAM (i.e. you are thrashing to HDD).

Reply 3 of 14, by reodraca

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Horun wrote on 2023-04-18, 02:45:

Depends on the TAG ram size. https://theretroweb.com/chipsets/578#VL82C591
You can check the manuals of other boards with same cache controller: https://theretroweb.com/motherboards/?chipset … 78&showImages=1

I don't see the TAG SRAM anywhere on the motherboard, although I will do a more in-depth search via the chip numbers later on. I am used to such a chip being the 5th or 9th chip on a Socket 3 486 motherboard, but this uses a COASt with a proprietary pinout. If the TAG's on the COASt, then there's a good chance it is indeed only 64 MB cachable since the 256k COASt my system has seems to be the lowest option.

Thank you for your advice!

Reply 4 of 14, by reodraca

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dionb wrote on 2023-04-18, 11:42:
Actually the early Intel Pentium chipsets had much higher cacheable limits - i430NX could cache 512MB of RAM. It was only after […]
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Actually the early Intel Pentium chipsets had much higher cacheable limits - i430NX could cache 512MB of RAM. It was only after Pentium moved into the mid/low-end with i430FX in 1995 that Intel cost-cut that to 64MB max.

As for the VLSI 590 - it seems to be the same as with the i430HX: with one tag it's limited to 64MB, with a second tag it can go up to 512MB.

If unsure about your board, install >64MB and run the CTCM tool (not to be confused with the Creative utility of same name). It should tell you how much of your RAM is cacheable.

Be aware that more RAM than your programs need never increases performance (at least not with vintage PC OSs), so as a rule it's fastest to stay under cacheable limits unless you're very sure you need more RAM (i.e. you are thrashing to HDD).

I know that it's pointless to add more RAM for vintage PC's since most programs of the time don't use them, but I was thinking of testing this system's limits by installing NT 4.0 Workstation and specifically picking programs that would've required more RAM at the time. I know that a single socket Pentium is hardly a decent candidate for such applications, but I'm extremely curious. This would be a task better suited to my dual Pentium Pro, to be sure, but it's more fun to see what systems that weren't built for heavy performance can do under complete utilisation.

I will try that program. Thanks!

Reply 5 of 14, by H3nrik V!

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IIRC, NT based OS will use memory from the bottom up, ie use cached memory first, so you won't have as big a negative impact on speed if only 64 megs is cacheable, as if you'd run 9x for example ...

Please use the "quote" option if asking questions to what I write - it will really up the chances of me noticing 😀

Reply 6 of 14, by dionb

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reodraca wrote on 2023-04-19, 03:55:

[...]

I don't see the TAG SRAM anywhere on the motherboard, although I will do a more in-depth search via the chip numbers later on. I am used to such a chip being the 5th or 9th chip on a Socket 3 486 motherboard, but this uses a COASt with a proprietary pinout. If the TAG's on the COASt, then there's a good chance it is indeed only 64 MB cachable since the 256k COASt my system has seems to be the lowest option.

Thank you for your advice!

Most likely it is on the COAST only.

Do you have a good pic of the board? The best I can find is this, but apart from showing that there is a tag on the COAST, does not show enough to rule out any more tag.

1024px-G620-4.jpg

Reply 7 of 14, by reodraca

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dionb wrote on 2023-04-19, 07:15:
Most likely it is on the COAST only. […]
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reodraca wrote on 2023-04-19, 03:55:

[...]

I don't see the TAG SRAM anywhere on the motherboard, although I will do a more in-depth search via the chip numbers later on. I am used to such a chip being the 5th or 9th chip on a Socket 3 486 motherboard, but this uses a COASt with a proprietary pinout. If the TAG's on the COASt, then there's a good chance it is indeed only 64 MB cachable since the 256k COASt my system has seems to be the lowest option.

Thank you for your advice!

Most likely it is on the COAST only.

Do you have a good pic of the board? The best I can find is this, but apart from showing that there is a tag on the COAST, does not show enough to rule out any more tag.

1024px-G620-4.jpg

I think I can do you one better: I believe I found the TAG chip on the COASt. Its number is IDT71B74. Furthermore, there's only one such chip. From what I can tell, it therefore has the 64 MB cacheable limit. Either that, or my tech savviness hits a wall when I encounter complicated datasheets, and I am completely misinterpreting whatever texts I find. Here's a photo anyway:

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Also, I think I see the same TAG chip on the photo you sent of yours.

Reply 8 of 14, by reodraca

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H3nrik V! wrote on 2023-04-19, 04:02:

IIRC, NT based OS will use memory from the bottom up, ie use cached memory first, so you won't have as big a negative impact on speed if only 64 megs is cacheable, as if you'd run 9x for example ...

True, but the whole point of this experiment would hinge on whether or not this AT&T system can cache its own maximum RAM amount (192 MB), rather than only a third of it. Otherwise, there's no point and I'd just reduce it to 64 MB. I want to see how fast this thing can handle stuff, and any slowdowns would skew the results if I run any programs exceeding the use of a 64 MB maximum.

Reply 9 of 14, by majestyk

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The mainboard is a FIC PSK-2000 - the cache stick is proprietary and also made by FIC .

I experimented with this board a lot and there´s a thread about it here at Vogons.
FIC PSK-2000 LPX Mainboard (AT&T Globalyst 630) proprietary hell

Datasheets about this chipset are virtually unavailable!
There´s a vacant place for a 2nd TAG chip on your cache stick. For an enlarged cache range the additional TAG lines be must wired to the MCH. I don´t know if this is the case here.
If the present TAG chip "M1" is 8Kx8 and if the Intel HX logic applies you would not only have to populate the second TAG chip (M2) but also make sure both are 16K x 8 or 32K x 8.

Reply 10 of 14, by reodraca

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majestyk wrote on 2023-04-20, 02:41:
The mainboard is a FIC PSK-2000 - the cache stick is proprietary and also made by FIC . […]
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The mainboard is a FIC PSK-2000 - the cache stick is proprietary and also made by FIC .

I experimented with this board a lot and there´s a thread about it here at Vogons.
FIC PSK-2000 LPX Mainboard (AT&T Globalyst 630) proprietary hell

Datasheets about this chipset are virtually unavailable!
There´s a vacant place for a 2nd TAG chip on your cache stick. For an enlarged cache range the additional TAG lines be must wired to the MCH. I don´t know if this is the case here.
If the present TAG chip "M1" is 8Kx8 and if the Intel HX logic applies you would not only have to populate the second TAG chip (M2) but also make sure both are 16K x 8 or 32K x 8.

I actually read your thread a while ago. If you read my first post in this topic, you'll see me refer to the idea of installing a VRM for use with an MMX chip. I got that idea from you, although I've chosen to keep this system as stock as possible, sans the upgrade to 133 MHz from the original 90. This system's even got its original hard drive, a Caviar 31000 in perfect platter and bearing health.

For that reason, I've also decided not to alter what is already a clearly rare COASt module in a rare system with an even rarer chipset. If it's only got the 1 TAG chip, then I'll accept 64 MB as the max for this system for now. Perhaps if I come across a second AT&T COASt, I'll be a bit braver about altering one of them.

Also yeah, something tells me that the VLSI chipset wasn't really that widely adopted. That's especially considering how Intel was really starting to throw down the gauntlet in the chipset arena when they developed the Pentium. VLSI had a lot more spotlight in the 80s and very early 90s, I believe. There's no surprise that next to no documentation is available for the SuperCore 590, 30 years after its introduction.

Reply 11 of 14, by majestyk

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Agreed. Due to it´s rarity I kept a second PSK-2000 (complete with cache stick) that I left unmodified.

It´s a fine LPX mainboard as it is and the FIC cache stick is even rarer than the one made by "SMART".

Reply 12 of 14, by reodraca

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majestyk wrote on 2023-04-20, 03:38:

Agreed. Due to it´s rarity I kept a second PSK-2000 (complete with cache stick) that I left unmodified.

It´s a fine LPX mainboard as it is and the FIC cache stick is even rarer than the one made by "SMART".

I like FIC as a brand in general. I once had an SD-11 Athlon motherboard from them (Compaq OEM called Aspen2) that treated me very well with Windows 98 games. They seem to be highly reliable, so it's no wonder that AT&T/NCR picked them to build their motherboards.

Reply 13 of 14, by hyoenmadan

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reodraca wrote on 2023-04-20, 03:19:

Also yeah, something tells me that the VLSI chipset wasn't really that widely adopted. That's especially considering how Intel was really starting to throw down the gauntlet in the chipset arena when they developed the Pentium.

They were busier doing chipsets for non-x86 platforms, like M68k Macs and later ARM and PPC hardware.
With Intel covering the premium range and Taiwanese covering the mass produced and cheap chipset market, VLSI would see no interest spending their efforts in the x86 oversaturated arena.

Reply 14 of 14, by reodraca

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hyoenmadan wrote on 2023-04-20, 20:22:
reodraca wrote on 2023-04-20, 03:19:

Also yeah, something tells me that the VLSI chipset wasn't really that widely adopted. That's especially considering how Intel was really starting to throw down the gauntlet in the chipset arena when they developed the Pentium.

They were busier doing chipsets for non-x86 platforms, like M68k Macs and later ARM and PPC hardware.
With Intel covering the premium range and Taiwanese covering the mass produced and cheap chipset market, VLSI would see no interest spending their efforts in the x86 oversaturated arena.

To clarify, I meant Intel didn't widely adopt VLSI's chipset for their Pentium's. I have plenty of classic Macs with VLSI chips, my favorite being my LC III.