Nehalem and 4 Gbit DDR3

Posted on February 5, 2021 by Michal Necasek

While discussing Intel desktops with DDR2 memory using 2 Gbit technology (4 GB UDIMMs), the question of Intel’s next generation and 4 Gbit DDR3 (8 GB UDIMMs) came up. It’s more or less the next iteration of exactly the same problem.

I decided to focus on the LGA1366 platform which was the first post-Core 2 generation and Intel’s first platform that used exclusively DDR3 memory (recap: later Core 2 chipsets supported both DDR2 and DDR3). Reviewing Intel’s documentation turned out to be… confusing.

The datasheet for the first generation Bloomfield Core i7 (45nm Core i7 LGA1366, Nehalem microarchitecture) says that DDR3 “512Mb, 1Gb, 2Gb, technologies/densities are supported”, 24 GB RAM maximum. The memory controller in the CPUs could handle 6 DIMMs, and with 2 Gbit technology/4 GB UDIMMs, that obviously results in 24 GB maximum.

Can this 2008 desktop CPU support 48 GB RAM? Intel says no…

The datasheet for the follow-up Gulftown processors (32nm Core i7 LGA1366, Westmere microarchitecture) does not state what technologies or memory limits are supported. It was not hard to find reports of people using Westmere generation LGA1366 CPUs with 48 GB RAM so I started digging further.

I only have one desktop LGA1366 board that could possibly take 48 GB RAM, Intel’s own DX58SO2 (Smack Over 2). That’s where it gets interesting. The DX58SO2 Technical Product Specification clearly says 24 GB maximum. But the DX58SO2 Product Brief just as clearly says “Maximum system memory up to 48 GB using 8 GB double-sided DIMMs.” Who do you trust, Intel or Intel? Could they be both wrong?

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Posted in Intel, PC hardware, PC history | 12 Comments

The Phantom Intel GM47 Chipset

Posted on February 2, 2021 by Michal Necasek

I spent a bit of time recently putting together technical documentation for Intel’s 4-series chipsets, partly motivated by research into Intel’s support of 4 GB DDR2 memory modules, partly driven by idle curiosity about one of Intel’s many hyped up and failed projects, Turbo Memory.

There are plenty of mentions of the Intel GM47 chipset. And that Turbo Memory article explicitly says that Intel’s Turbo Memory 2.0 is available on the Cantiga GM47 chipset as announced by Intel on July 15, 2008. Although the phrasing in the Wikipedia article may be misleading in that Turbo Memory 2.0 was probably available on the Cantiga (Mobile 4 Series) chipset and not just GM47. of course there’s no reference given for the statement… so who knows.

At any rate, there were certainly rumors that GM47 was to be released in 2008, and then in Q1 2009. But then 2009 came and there was no GM47 chipset. It appears to have gotten Intel’s typical second-class burial—a decree comes from up on high, the victim product is no longer mentioned, must not be spoken of, and references to it are scrubbed. Thus GM47 is notable only by its absence, say, here on Intel’s ark, or in the Mobile 4 Series Chipset Specification Update.

Perhaps the somewhat confusing status of the GM47 chipset’s existence is what led to curious statements like the one in this Italian Wikipedia article. “Cantiga (the 4-series mobile chipset) is marketed in three variants: GM47, GM45, GS45, PM45.” Now which one of the four listed was not actually marketed?

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Posted in Intel, PC history, PC press | 7 Comments

DDR2 4GB DIMMs

Posted on January 29, 2021 by Michal Necasek

Last week the OS/2 Museum got its first ever set of real (i.e. not fake) 4 GB DDR2 desktop (unbuffered) DIMMs, a pair of Samsung 4GB PC2-6400U modules. Such modules are quite rare and correspondingly tend to be unavailable at a reasonable price. Moreover there is a lot of fake “AMD only” modules. But why are the real DDR2 4 GB UDIMMs so rare?

The short answer is “because they’re almost useless”.

The long answer is that DDR2 modules based on 2 Gbit memory technology became available too late in the DDR2 life cycle, which led to such modules being rather poorly supported. They are not unsupported—there are DDR2 boards which not only accidentally happen to work with such modules but where the manufacturers officially support them.

A case in point is the Intel DQ45CB board. It came out in mid-2008 and when it was released, it did not list 4 GB modules as supported, most likely because they weren’t available. The board has four memory slots and it was initially specified to support up to 8 GB memory maximum (with four 2 GB modules). Sometime between April 2009 (specification update E53961-004US) and May 2010 (specification update E53961-006US), Intel officially changed the board’s specification to support up to 16 GB RAM when using 4 GB DIMMs based on 2 Gbit memory technology.

SPD for Samsung 4 GB DDR2 UDIMM (Intel DQ45CB board)

Obviously at that time DDR3 RAM was already available. In fact the same Intel Q45 chipset supports both DDR2 and DDR3 (though any given board would naturally only support one or the other type). This led to some curious situations; the above mentioned Intel DQ45CB board eventually supported up to 16 GB DDR2 memory, but the “better” DP45SG board from the same generation used DDR3 memory and never (at least officially) went beyond 8 GB maximum memory support.

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Posted in DDR RAM, Fakes, PC hardware | 22 Comments

Booting Windows XP, Or Not

Posted on January 22, 2021 by Michal Necasek

For a number of years now I’ve been using a SATA SSD with a “portable” Windows XP installation on it. Portable in the sense that it was capable of booting on a number of my machines, either in IDE mode or in some cases, in AHCI mode. But not anymore—now it no longer booted on some boards either in IDE or in AHCI mode, and failed with everyone’s favorite, bug check 0x7B (INACCESSIBLE_BOOT_DEVICE). I couldn’t make heads nor tails of it; it still worked perfectly fine on a number of boards, but on some it just wouldn’t boot.

I suspected that this was triggered by my failed attempts to get the XP install booting on my DX79SR Stormville board in AHCI mode. In the end I concluded that it couldn’t be done, but not before I tried installing several different AHCI drivers; to be clear, those drivers did make a difference—they made the OS crash at boot-up with bug check 0x7E (completely different from 0x7B and indicating a buggy driver). The Stormville board has a somewhat uncommon IDE/AHCI chip (related to the C600 chipset rather than any Intel desktop chipset) and it was released late enough (2011) that XP support was not provided.

After my failed experiments, I was no longer able to boot on the Stormville board even in IDE mode. I was also no longer able to boot that XP install on an older Intel D975XBX2 (Bad Axe 2) board, which previously worked fine in AHCI mode. But now it just sulked and gave me INACCESSIBLE_BOOT_DEVICE in both IDE and AHCI mode.

I attempted various fixes including a number of attempts of fix_hdc from Hiren’s boot CD. It did something, but that definitely did not include getting rid of the INACCESSIBLE_BOOT_DEVICE bug checks.

In desperation, I hooked up the XP install to a kernel debugger. It was already set up for kernel debugging (not that it would have been hard to do) and the Bad Axe 2 board is old enough to have a real serial port on the back panel. I booted up with the SATA controller in AHCI mode and kernel debugger attached. What the kernel debugger told me was odd.

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Posted in Debugging, PC hardware, Windows XP | 16 Comments

Seek and Ye Shall Find…

Posted on January 20, 2021 by Michal Necasek

…in the strangest places!

Lately I’ve been digging up marketing materials related to Intel’s desktop boards (I’ve long been toying with the idea of writing up a brief history of the circa 10 years of Intel Extreme Series boards).

There is no real archive of the information but random PDFs from years ago pop up in various places, most often various computer resellers around the world, sometimes academic institutions. But this Intel desktop board product matrix from 2004 really takes the cake—check out the URL. It is not fake.

Also note that this is the only copy of said PDF (Intel Confidential!) on the web. It only survived because of Al Qaeda and CIA. $DEITY sure works in mysterious ways.

Posted in Archiving, Intel, PC hardware, PC history | 2 Comments

It’s In Style Now

Posted on January 10, 2021 by Michal Necasek

Retrocomputing has now made it to the Style section of the New York Times. There is nothing particularly new about the article, except where it appeared. I guess people have noticed that retrocomputing is a thing, and that old gear is quickly turning into collectibles.

For my own part, I was very lucky that the OS/2 Museum acquired some equipment before retrocomputing was a thing. For example PS/2 machines are now worth hundreds of dollars, and I got a few at a time when shipping cost more than the machine.

These days, I find that prices of 5-10 year old server gear can be surprisingly low, although high-end desktop boards and CPUs still sell for surprisingly high prices (Core 2 Extreme, Core i7 Extreme) that never dropped down enough to reflect their actual practical value. Interesting times.

Posted in PC history, PC press | 10 Comments

Disabling Quick Edit Mode

Posted on December 18, 2020 by Michal Necasek

Last week I decided to finally solve a minor annoyance that’s been pestering me since I switched my main development machine from Windows 7 to Windows 10 over a year ago. As it is with these things, a certain threshold of pain needs to be reached before delving into the unknown, because one never knows how many rabbit holes it will lead to.

The problem: Every now and then, I use the Open Watcom tools, often for cross-development to DOS or OS/2. When I do that, I tend to use the console-based tools, including the vi editor and wd debugger, in part because they work the same across platforms. Both tools can work with a mouse, and especially the debugger is just much productive when used with a mouse. On Windows 7, that works fine. Not so much on Windows 10, because instead of sending mouse events to the application, Windows tries to select text in the console window. Not helpful:

Quick Edit Mode makes the mouse unusable for a console application

Anyone who has fought with this problem probably knows the answer: Quick Edit Mode. When Quick Edit is enabled, mouse selects text from the console window, Enter copies, right-click pastes. Great for a shell, much less so in a mouse-driven text mode UI. On Windows 10, Quick Edit mode is on by default, and that is what caused me grief.

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Posted in NT, Undocumented, Watcom | 22 Comments

The Answer To 0x49: Fujitsu FMR

Posted on December 11, 2020 by Michal Necasek

This is a guest post by A. N. Other.

The following was originally intended as a comment to “Not MSX Either“, the 4th installment in the hunt for the mysterious 0x69 FAT VBR-start byte which was allowed in DOS. Due to the length and content I was asked to turn it into a guest-post, presented below.

Definitive answer to 0x49, leading to new speculations about 0x69.

First let me thank Octocontrabass for the golden tip that got things rolling!
Also bleuge for your marvelous effort (I’m very curious to some info about [46; 2E; 262]…).

I got into this matter as my fuzzy tester uncovered 0x49. Further testing did indeed show that MS was checking for 0x49 for >25 years and that it indeed still does so for Win10, instead of 0x69 as stated on Wikipedia (and corresponding talk page, in fact there is currently no mention of the reality of 0x49).

It is this 0x49 that, for practical reasons, interested me the most. And who knows, it might give some insight into the 0x69 (and I will end with some new theories about this based on the facts regarding to 0x49).

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Posted in DOS, NT, PC hardware, PC history, Undocumented | 7 Comments

Every Bit Matters

Posted on December 4, 2020 by Michal Necasek

A couple of months ago the OS/2 Museum got hold of a 13.6 GB Fujitsu MPE3136AT IDE drive from 1999. The drive was working… more or less. It behaved quite strangely; the drive was detected and readable, but seemed oddly slow. It should have been capable of Ultra DMA transfers but delivered data at just under 2 MB/sec.

Fujitsu MPE3136AT IDE drive

Looking through Linux dmesg output, it was apparent that the system was trying to communicate with the drive at Ultra DMA speeds, but kept falling back to slower PIO speeds due to CRC errors. Oddly, the drive vendor was also shown as FUBITSU, rather than FUJITSU as one would expect.

And looking at the data the drive returned, it was clear that it was somehow corrupted. For example messages in the boot sector clearly had some letters wrong, but only some.

What could possibly cause such a problem?

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Posted in Fixes, PC hardware, Storage | 7 Comments

Decoding Seagate Date Codes

Posted on November 27, 2020 by Michal Necasek

More or less everyone knows that throughout the 1990s and 2000s, Seagate did not label their drives with a date of manufacture like everyone sane would do, but instead used a custom and somewhat mysterious/confusing “date code”. For reasons that I’m sure made sense to Seagate, but definitely made no sense to Seagate’s customers, the date code refers to Seagate’s fiscal year rather than a calendar year.

The good news is that Seagate no longer uses the cryptic date codes and prints a full date of manufacture on their drive labels, just like everyone else. The bad news is that there are countless millions of Seagate drives made before 2016 or so out there, and most of those drives only have the hard to decipher date code.

When was this Seagate drive made? It’s a mystery…

The four- or five-digit date code consists of a two-digit year, one- or two-digit week number (starting with 1), and one-digit day of the week (again starting with 1). If the week number is less than 10, the leading zero may be left out; that seems to have been the case on older drives, but later Seagate apparently switched to consistent five-digit codes.

Now, there are several online Seagate date conversion tools. So far, I have not found one that actually works properly. That is, they produce a date which is close but very often off by several days or even a week. While the few days probably don’t really matter in the end, I find it unnerving and sloppy, especially because it’s obvious that one can do better than that.

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Posted in PC history, Seagate, Storage | 5 Comments