Percussive Maintenance

Posted on November 25, 2020 by Michal Necasek

A couple of weeks ago this antique 1997 Cheetah 9 drive showed up at the OS/2 Museum:

A fat Cheetah

It was effectively a freebie, a faulty drive bought together with another, more desirable, and working drive. (Well, initially working, but that’s a whole different story.) Now, the model ST19101W Cheetah is historically an interesting drive, since it’s the first generation Cheetah, and those Cheetahs were the first 10,000 RPM drives ever. There were two models, Cheetah 4LP (1″ high) and Cheetah 9 (1.6″ high), with 4 and 9 GB capacities, respectively. When the Cheetah first became available, it was “unquestionably the fastest hard drive ever made” according to Red Hill.

This particular Cheetah 9 was quite sick and would not spin up. It was clearly trying to spin but failing, resulting in an endless cycle of attempted spin-up, beep, attempted spin-up, beep, and so on. The beeping was most likely resonance from the voice coil actuator, since the drive has no built in beeper.

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Posted in Hardware Hacks, Seagate | 7 Comments

Those Lot Numbers are Old

Posted on October 24, 2020 by Michal Necasek

The other day I was trying to decode the “lot numbers” printed on certain Seagate drives. In the meantime, I realized that those lot numbers have been in use for quite some time. They were in use around 2000, like on this Cheetah 73 made in 2001:

Seagate Cheetah label (2001)

They can be found on Seagate’s drives going back into the early 1990s, but always only on some of them—typically on higher-end enterprise drives, almost exclusively using SCSI/FC/SAS interfaces. One older example is this 1994 DEC-branded RZ25-E drive, which is definitely a Seagate-made drive and almost certainly a model ST1480N:

Digital RZ25-E (Seagate ST1480N) label

As it turns out, those lot numbers aren’t a Seagate invention. It’s something that Seagate adopted when it acquired (1989) the drive maker Imprimis, a subsidiary of CDC (Control Data Corporation).

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Posted in PC history, Seagate | 11 Comments

Not MSX, Either

Posted on October 7, 2020 by Michal Necasek

Further examining the mystery of boot sectors supposedly starting with byte value 69h, I considered the possibility that the check could have been added for MSX machines. The MSX platform ticks a lot of boxes: It wasn’t 8086 (but rather Z80), used 3.5″ floppies, used FAT format, appeared around 1985, and Microsoft was involved in it.

But looking closer, MSX is quite unlikely for one simple reason: Microsoft was clearly concerned about data exchange with PCs, and solved the problem differently. MSX floppy boot sectors actually start with the usual 8086 instructions, and if they’re booted on an MSX machine, the boot sector starts execution at offset 1Eh.

Not only that, but the MSX BIOS in fact requires that the floppy boot sector must start with byte EBh or E9h to be considered bootable at all.

The above is clearly documented in the MSX Technical Data Book (published by Sony in 1984). Extant MSX floppy images confirm the documentation—MSX floppies use 8086 opcodes in the first three bytes.

But wait, there’s more…

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Posted in IBM, Microsoft, PC history | 15 Comments

Return to Stormville

Posted on September 29, 2020 by Michal Necasek

A while ago I griped about a strangely ill-behaved Intel DX79SR Stormville board. To recap, the board simply refused to take any memory in the 4th memory channel. Since then, there have been very interesting new development in the story.

I found another complaint about these boards that exactly matches my symptoms. I missed it at first because it doesn’t mention the DX79SR board (it’s about DX79SI/TO). To recap, in 2011, Intel came out with two boards based on the X79 chipset, DX79SI (Siler) and a slightly stripped down and cheaper DX79TO (Toler). In 2012, the DX79SI was replaced by DX79SR with more USB 3.0 ports and more 6Gbps SATA ports. The three boards all use the same PCB, same BIOS, and are for most intents and purposes identical. It is therefore unsurprising that they’d also have the same problems.

Worth noting is that near the end of the discussion, a user claimed to have fixed just such problem by straightening a bent pin in the CPU socket. Since the memory controller is on the CPU, that is not implausible, although I could not find any sign of a bent pin on my Stormville board.

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Posted in Bugs, Intel, PC hardware | 3 Comments

Really Atari ST?

Posted on September 21, 2020 by Michal Necasek

This blog has previously examined a very very strange code fragment in the BIOS module of DOS. To recap, when deciding whether a boot sector might have a valid BPB, DOS checks whether the first byte is a relative jump (opcode E9h) or a short jump (opcode EBh), both used by different DOS versions. But it also checks for a “direct jump” with 69h opcode.

The code looks like this in the MS-DOS 3.21 OAK, source file dated May 1, 1987:

         cmp    byte ptr cs:[DiskSector],069H   ; Is it a direct jump?
         je     Check_Signature                 ; don't need to find a NOP
         cmp    byte ptr cs:[DiskSector],0E9H   ; DOS 2.0 jump?
         je     Check_Signature                 ; no need for NOP
         cmp    byte ptr cs:[DiskSector],0EBH   ; How about a short jump.
         jne    BadDisk
         cmp    byte ptr cs:[DiskSector]+2,090H ; Is next one a NOP?
         jne    BadDisk

The code is not materially different in the MS-DOS 3.3 OAK, source file dated July 24, 1987:

         cmp    byte ptr cs:[DiskSector],069H   ; Is it a direct jump?
         JE     Check_bpb_MediaByte             ; DON'T NEED TO FIND A NOP
         cmp    byte ptr cs:[DiskSector],0E9H   ; DOS 2.0 jump?
         JE     Check_bpb_MediaByte             ; NO NEED FOR NOP
         cmp    byte ptr cs:[DiskSector],0EBH   ; How about a short jump.
         JNE    INVALIDBOOTSEC
         cmp    byte ptr cs:[DiskSector]+2,090H ; Is next one a NOP?
         JNE    INVALIDBOOTSEC

The labels are different but the logic is identical. But of course there is no such “direct jump” on x86, and the 69h opcode (undocumented on 8086, IMUL on later CPUs) makes no sense whatsoever. So what is it?

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Posted in DOS, Microsoft, PC history | 18 Comments

Seagate Serial Talk

Posted on August 5, 2020 by Michal Necasek

Some time ago, the OS/2 Museum obtained a 10 GB Seagate ST310014ACE hard disk (IDE 3.5″ low profile). The disk was unusable because it was locked. That is, it needed an unknown password to gain access to the medium.

Seagate ST310014ACE drive

After a few quick searches it turned out that this problem is surprisingly common. The particular model of hard disk was used in the first generation Xbox consoles and indeed it was locked there, which meant that after taking it out of the Xbox the disk was no longer usable.

Except there is a way to unlock these drives, using a serial terminal, a special adapter, and a couple of magic commands. How does that work?

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Posted in Hardware Hacks, PC hardware, Seagate | 22 Comments

Breaking Into ASOS

Posted on August 1, 2020 by Michal Necasek

The OS/2 Museum recently acquired a Quantum Bigfoot TS hard disk in mint condition. The Bigfoot drives, as some readers may remember, were rather oddball late-1990s 5.25″ IDE drives that were cheap, slow, and relatively big. There was a sticker on the disk that suggested the drive once lived inside a Compaq machine. After attaching the disk to a Linux system, it turned out that the drive was not empty but the contents were too foreign for Linux to handle.

After hooking up the image of the drive to a VM, it turned out that the drive is not only bootable but actually boots into some… bizarre thing that Compaq and SCO cooked up. Here’s what the screen looks like when booted up:

Some kind of Microsoft/SCO/Compaq server?

Not much to see there. At all. After switching the virtual terminal (with Alt-F2, where did you think Linux stole that idea?) it turned out to be a curious mix of an off-the-shelf OS with some heavy custom tweaking:

Compaq ASOS, a customized SCO OpenServer

Okay, so it’s SCO OpenServer Release 5, but with some sort of Compaq modifications. With the “ASOS” keyword there’s something to search for. It turns out the hard disk came out of a Compaq Prosignia NeoServer, an oddball late-1990s network server. In other words, a low-powered cheapo Celeron PC running a web server, file server, print server, etc., all remotely manageable. For whatever reason, Compaq decided to base that on top of SCO OpenServer. The NeoServer looked a bit like a shredder or a trash can but it was 1999 and it said “network” and “internet” so it had to be good. A significant chunk of the NeoServer functionality relied on a product called VisionFS, which was roughly similar to Samba.

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Posted in Compaq, PC history, SCO | 4 Comments

X7DBE WTF

Posted on July 23, 2020 by Michal Necasek

Several years ago I got two Supermicro X7DBE boards at a bargain price. These are nice dual Socket 771 boards of circa 2007 vintage, built around the Intel 5000P Blackford chipset and using FB-DIMMs with up to 32GB memory supported.

Recently I pulled one of the boards out of storage and installed two quad-core Harpertown Xeon E5450 processors in it, primarily for the purpose of verifying that newly arrived FB-DIMMs work. The memory worked just fine… but something else didn’t.

The CPUs ran at only 1.2 GHz (instead of 3.0 GHz), and even worse, one of the CPUs was not recognized. I swapped the CPUs around but that didn’t change anything—one was still not recognized. I plugged in two slightly slower Xeon E5430 CPUs… and one still wasn’t recognized, and instead of 2.66 GHz the CPUs ran at 1.06 GHz. I thought the board perhaps got damaged during moving and didn’t investigate further.

Sometime later I pulled out the other X7DBE board. It had two E5430 Xeons installed already. When I first tried it, both CPUs were recognized, running at 2.66 GHz as they should. Board clearly working.

So I thought, let’s put the faster E5450s in it. I did… and one of them wasn’t recognized, while the other ran at 1.2 GHz! I put the original E5430s back, but oops, one wasn’t recognized and the other ran at 1.06 GHz.

Okay, this is really weird. In desperation, I put in two Dempsey 5080 Xeons, the latest and greatest (if such a thing can be said) NetBurst Xeons. And again, one of them was not recognized, although the other at least ran at the full 3.73 GHz. Hmm…

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Posted in PC hardware, Supermicro, Xeon | 18 Comments

Well Hello

Posted on July 14, 2020 by Michal Necasek

So after some furious disassembling, assembling, and linking, things got this far:

Freshly built GW-BASIC

It took longer than it ought to have because although IDA is great, I couldn’t figure out how to make it work with GW-BASIC’s bizarre segment usage. The problem is that the BASIC data segment is tacked onto the end of the code, and during initialization, CS equals DS and variables have high offsets in the segment. But after initialization, CS no longer equals DS and DS points at the beginning of the data, which means variables are at low offsets within DS. I failed to convince IDA that the same data is accessed through completely different offsets at different points in the code. After a lot of trying and failing, I’m still unsure if I’m doing something wrong or if it’s really a situation that IDA can’t adequately handle.

At any rate, I ended up with a bit over four thousand lines of a GW-BASIC OEM module, lovingly borrowed from Compaq’s BASICA.EXE version 1.13.

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Posted in Compaq, Microsoft, PC history, Source code | 7 Comments

How Old Is OMF?

Posted on July 9, 2020 by Michal Necasek

The Object Module Format (OMF), used by most DOS development tools, and eventually displaced by COFF/ELF in the 32-bit world, is quite old. It is a somewhat strange format because of its age, and it is quite complex, both because it was designed for the segmented 8086 architecture and because it evolved over many years.

The LINK.EXE linker supplied with DOS 1.0 (1981) used OMF as the input format and Microsoft’s development tools (MASM, Pascal, etc.) produced it. Just about all major 16-bit 8086 compilers use OMF by default. OMF must be at least as old as DOS then.

Wikipedia claims that OMF “was originally developed by Intel in 1981” and bases the claim on the fact that Intel published an 8086 OMF specification in 1981. Anyone actually reading that specification will wonder why a specification supposedly developed in 1981 and published that year is already at version 4.0.

The answer is of course that OMF is several years older than that and was likely developed closer to the mid-1970s than to 1981.

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Posted in Development, Intel, Microsoft, PC history, x86 | 8 Comments