The 8088 is as 16 bit processor.

Caluser2000 wrote on 2021-05-28, 04:28:

The 8088 is as 16 bit processor.

8086 is 16bit, while 8088 is 8bit. Both I think have 16bit address lines, but 8088 has 8bit data lines and 8bit registers, while the 8086 has 16bit data lines and 16bit registers.

videogamer555 wrote on 2021-05-28, 04:31:

Caluser2000 wrote on 2021-05-28, 04:28:

The 8088 is as 16 bit processor.

8086 is 16bit, while 8088 is 8bit. Both I think have 16bit address lines, but 8088 has 8bit data lines and 8bit registers, while the 8086 has 16bit data lines and 16bit registers.

You are incorrect https://spectrum.ieee.org/tech-history/silico … -microprocessor

DOSBox-X already supports Japanese PC-98 mode. There is a lot of code added because of PC-98 support, since the hardware is in fact very different, and DOS is pretty much the only thing in common when it was actually implemented. You can find the PC-98 guide page in the DOSBox-X Wiki:

Guide: PC-98 emulation in DOSBox-X

videogamer555 wrote on 2021-05-28, 04:23:

The PC-98 (full name being PC-9801) is a computer made by NEC, and only ever sold in Japan. It does use an intel CPU, specifical […]
Show full quote

The PC-98 (full name being PC-9801) is a computer made by NEC, and only ever sold in Japan. It does use an intel CPU, specifically a 16-bit Intel 8086. This is different than the IBM-PC, which had an 8-bit 8088 CPU, though unlike the next generation of IBM machines (which used 16-bit 80286 CPUs), the 8086 doesn't have all the extra instructions supported by the 80286. It's basically an Intel 8088, but with 16-bit registers, instead of 8-bit registers. As far as I know, no computers sold in the US used an 8086 CPU, so I don't know if DOSBox can handle 8086 emulation, but if it can, then theoretically it can emulate a PC-98.

However there are other differences between old US IBM (and compatible) computers, and the Japanese PC-98. For one, its graphics hardware directly supports 2 different graphics modes, not supported by standard graphics hardware in US computers. The PC-98 supports these 2 unique graphics modes: 640x400 16-color mode and 640x400 256-color mode. However, if you look at a list of the standard graphics modes from 0x00 to 0x13 (which can be switched to with a simple INT instruction in assembly code, and are supported by most US sold computers), and look at the specs for these modes, you'll notice that none of them support the same resolution and palette-size combinations as the 2 previously mentioned PC-98 resolutions. While I assume that the PC-98 may also support the standard resolutions from IBM CGA, EGA, and VGA graphics cards, it also supports some unique graphics modes.

Of course. The situation is the same with the Tandy and PC-Jr, with them having unique graphics modes too, but DOSBox (when set to Tandy or PC-Jr emulation mode) can properly emulate their unique graphics modes as well. So theoretically it should still be possible for DOSBox to properly emulate the unique graphics modes of the PC-98. Of course there's also the language issue. The PC-98 needs to have something that American PCs don't have, and that is both Japanese and English text character graphics (not sure if these are normally stored in BIOS memory, or built in to the firmware of the graphics card) builtin to the machine itself, and not requiring external font files for Japanese text characters to work. However this language issue is handled, I'm sure that there are enough documents floating around from reverse engineering efforts, that the proper way of handling this can be implemented in DOSBox when emulation mode is set to PC-98 in the DOSBox config file.

Given the fact that DOSBox aims to be a DOS games emulator, and given the fact that the 99% of the PC-98's software are games, it would make sense to add a PC-98 emulation mode to DOSBox.

Why not just a dedicated PC-98 emulator? Here's the problem with that. PC-98 emulators use their own proprietary disk image formats (either compressed disk image, or having its own header appended before the actual first sector of the disk image in the disk image file, or some combination of these techniques), while DOSBox is capable of directly loading raw floppy disk images. Editing PC-98 disk images (such as for modding a game) is a pain, as there's no really software for modifying the disk images. If I can convert the disk images formats (which are normally proprietary to a particular emulator) to raw disk images, I could use them directly in DOSBox, as DOSBox is capable of directly loading raw harddrive and floppy disk images, if you guys can implement a PC-98 emulation mode in DOSBox.

I don't know much about PC-98, but always wanted to come to know it better. I have a couple of questions. What are the top games on this platform to justify the effort of adding pc-98 mode?
And what is the sound system like on this platform? Does it also have separate FM and PCM(digital) subsystems? Does it reqiure DMA for PCM digital sound, or is it maybe even SB compatible?

videogamer555 wrote on 2021-05-28, 04:31:

Caluser2000 wrote on 2021-05-28, 04:28:

The 8088 is as 16 bit processor.

8086 is 16bit, while 8088 is 8bit. Both I think have 16bit address lines, but 8088 has 8bit data lines and 8bit registers, while the 8086 has 16bit data lines and 16bit registers.

Both the 8088 and 8086 are 16 bit processors. The only difference is that the 8088 has an 8 bit memory connection and the 8086 has a 16 bit memory connection. Internally both are the same.

Bondi wrote on 2021-05-28, 09:02:

videogamer555 wrote on 2021-05-28, 04:23:

The PC-98 (full name being PC-9801) is a computer made by NEC, and only ever sold in Japan. It does use an intel CPU, specifical […]
Show full quote

The PC-98 (full name being PC-9801) is a computer made by NEC, and only ever sold in Japan. It does use an intel CPU, specifically a 16-bit Intel 8086. This is different than the IBM-PC, which had an 8-bit 8088 CPU, though unlike the next generation of IBM machines (which used 16-bit 80286 CPUs), the 8086 doesn't have all the extra instructions supported by the 80286. It's basically an Intel 8088, but with 16-bit registers, instead of 8-bit registers. As far as I know, no computers sold in the US used an 8086 CPU, so I don't know if DOSBox can handle 8086 emulation, but if it can, then theoretically it can emulate a PC-98.

However there are other differences between old US IBM (and compatible) computers, and the Japanese PC-98. For one, its graphics hardware directly supports 2 different graphics modes, not supported by standard graphics hardware in US computers. The PC-98 supports these 2 unique graphics modes: 640x400 16-color mode and 640x400 256-color mode. However, if you look at a list of the standard graphics modes from 0x00 to 0x13 (which can be switched to with a simple INT instruction in assembly code, and are supported by most US sold computers), and look at the specs for these modes, you'll notice that none of them support the same resolution and palette-size combinations as the 2 previously mentioned PC-98 resolutions. While I assume that the PC-98 may also support the standard resolutions from IBM CGA, EGA, and VGA graphics cards, it also supports some unique graphics modes.

Of course. The situation is the same with the Tandy and PC-Jr, with them having unique graphics modes too, but DOSBox (when set to Tandy or PC-Jr emulation mode) can properly emulate their unique graphics modes as well. So theoretically it should still be possible for DOSBox to properly emulate the unique graphics modes of the PC-98. Of course there's also the language issue. The PC-98 needs to have something that American PCs don't have, and that is both Japanese and English text character graphics (not sure if these are normally stored in BIOS memory, or built in to the firmware of the graphics card) builtin to the machine itself, and not requiring external font files for Japanese text characters to work. However this language issue is handled, I'm sure that there are enough documents floating around from reverse engineering efforts, that the proper way of handling this can be implemented in DOSBox when emulation mode is set to PC-98 in the DOSBox config file.

Given the fact that DOSBox aims to be a DOS games emulator, and given the fact that the 99% of the PC-98's software are games, it would make sense to add a PC-98 emulation mode to DOSBox.

Why not just a dedicated PC-98 emulator? Here's the problem with that. PC-98 emulators use their own proprietary disk image formats (either compressed disk image, or having its own header appended before the actual first sector of the disk image in the disk image file, or some combination of these techniques), while DOSBox is capable of directly loading raw floppy disk images. Editing PC-98 disk images (such as for modding a game) is a pain, as there's no really software for modifying the disk images. If I can convert the disk images formats (which are normally proprietary to a particular emulator) to raw disk images, I could use them directly in DOSBox, as DOSBox is capable of directly loading raw harddrive and floppy disk images, if you guys can implement a PC-98 emulation mode in DOSBox.

I don't know much about PC-98, but always wanted to come to know it better. I have a couple of questions. What are the top games on this platform to justify the effort of adding pc-98 mode?
And what is the sound system like on this platform? Does it also have separate FM and PCM(digital) subsystems? Does it reqiure DMA for PCM digital sound, or is it maybe even SB compatible?

Some of the more well known games for the PC-98 were the Touhou games. The original Touhou games, were made only for DOS on the PC-98, and won't run on normal versions of DOS (DOS for the PC-98 was a special version that ran only on the PC-98, and supported features of the PC-98 not available on normal DOS PCs, such as the character set needed for all of those Japanese Kanji characters, that extends the number of characters well beyond the normal ASCII character set and even the extended ASCII characters). The Touhou games are actually a series that is still in production today though, but now with the games being available for Windows, and will run on any Windows PC, not just PCs sold exclusively in Japan. The original PC-98 Touhou games though were never remade for Windows though, and still require either a real PC-98, or a PC-98 emulator, to run. That's why I was hoping to get PC-98 emulation in DOSBox.

I don't know exactly what its sound system is, but if I remember correctly from some things I've read before, it's different enough from the normal SoundBlaster or Adlib type sound cards for normal PCs, that you'd need separate emulation code for it. I just did some research, and found that the oldest models had only a buzzer (not PC-speaker even, it just had one tone). Next there was a model that did have a PC-speaker, who's frequency was controlled by in interrupt timer. Later there were some models that supported sound cards like the PC-9801-26 sound card. Finally, on the latest models of PC-98 (which actually had an 80286 CPU in them, instead of the older 8086 CPU), they supported a PC-9801-26K soundcard (note the K at the end of the sound card's model number). These latest models usually came with the PC-9801-26K souncard already installed, based on my research. I found this info on the PC-9801-26K sound card:

This includes the Yamaha YM2203 OPN FM synthesizer, providing three 4-operator FM synthesis channels plus the three channels of the integrated YM2149 SSG unit.

I'm not sure what the "YM2149 SSG unit" is. Is it PCM audio? Or did all the soundcards for the PC-98 exclusively support FM synthesis based audio, with no PCM audio? Or was there also PCM audio capability as well? I assume there was PCM audio, as that's the most basic type of digital audio available.

I also read that the latest models of PC-98 also supported the PC-9801-86 soundcard (which had to be manually installed though), which supported 6 FM audio channels (rather than the normal 3), and also offered a few other features (though the source for my info didn't specify what the "few other features" were).

videogamer555 wrote on 2021-05-28, 20:14:

Some of the more well known games for the PC-98 were the Touhou games. The original Touhou games, were made only for DOS on the […]
Show full quote

Bondi wrote on 2021-05-28, 09:02:

videogamer555 wrote on 2021-05-28, 04:23:

The PC-98 (full name being PC-9801) is a computer made by NEC, and only ever sold in Japan. It does use an intel CPU, specifical […]
Show full quote

The PC-98 (full name being PC-9801) is a computer made by NEC, and only ever sold in Japan. It does use an intel CPU, specifically a 16-bit Intel 8086. This is different than the IBM-PC, which had an 8-bit 8088 CPU, though unlike the next generation of IBM machines (which used 16-bit 80286 CPUs), the 8086 doesn't have all the extra instructions supported by the 80286. It's basically an Intel 8088, but with 16-bit registers, instead of 8-bit registers. As far as I know, no computers sold in the US used an 8086 CPU, so I don't know if DOSBox can handle 8086 emulation, but if it can, then theoretically it can emulate a PC-98.

However there are other differences between old US IBM (and compatible) computers, and the Japanese PC-98. For one, its graphics hardware directly supports 2 different graphics modes, not supported by standard graphics hardware in US computers. The PC-98 supports these 2 unique graphics modes: 640x400 16-color mode and 640x400 256-color mode. However, if you look at a list of the standard graphics modes from 0x00 to 0x13 (which can be switched to with a simple INT instruction in assembly code, and are supported by most US sold computers), and look at the specs for these modes, you'll notice that none of them support the same resolution and palette-size combinations as the 2 previously mentioned PC-98 resolutions. While I assume that the PC-98 may also support the standard resolutions from IBM CGA, EGA, and VGA graphics cards, it also supports some unique graphics modes.

Of course. The situation is the same with the Tandy and PC-Jr, with them having unique graphics modes too, but DOSBox (when set to Tandy or PC-Jr emulation mode) can properly emulate their unique graphics modes as well. So theoretically it should still be possible for DOSBox to properly emulate the unique graphics modes of the PC-98. Of course there's also the language issue. The PC-98 needs to have something that American PCs don't have, and that is both Japanese and English text character graphics (not sure if these are normally stored in BIOS memory, or built in to the firmware of the graphics card) builtin to the machine itself, and not requiring external font files for Japanese text characters to work. However this language issue is handled, I'm sure that there are enough documents floating around from reverse engineering efforts, that the proper way of handling this can be implemented in DOSBox when emulation mode is set to PC-98 in the DOSBox config file.

Given the fact that DOSBox aims to be a DOS games emulator, and given the fact that the 99% of the PC-98's software are games, it would make sense to add a PC-98 emulation mode to DOSBox.

Why not just a dedicated PC-98 emulator? Here's the problem with that. PC-98 emulators use their own proprietary disk image formats (either compressed disk image, or having its own header appended before the actual first sector of the disk image in the disk image file, or some combination of these techniques), while DOSBox is capable of directly loading raw floppy disk images. Editing PC-98 disk images (such as for modding a game) is a pain, as there's no really software for modifying the disk images. If I can convert the disk images formats (which are normally proprietary to a particular emulator) to raw disk images, I could use them directly in DOSBox, as DOSBox is capable of directly loading raw harddrive and floppy disk images, if you guys can implement a PC-98 emulation mode in DOSBox.

I don't know much about PC-98, but always wanted to come to know it better. I have a couple of questions. What are the top games on this platform to justify the effort of adding pc-98 mode?
And what is the sound system like on this platform? Does it also have separate FM and PCM(digital) subsystems? Does it reqiure DMA for PCM digital sound, or is it maybe even SB compatible?

Some of the more well known games for the PC-98 were the Touhou games. The original Touhou games, were made only for DOS on the PC-98, and won't run on normal versions of DOS (DOS for the PC-98 was a special version that ran only on the PC-98, and supported features of the PC-98 not available on normal DOS PCs, such as the character set needed for all of those Japanese Kanji characters, that extends the number of characters well beyond the normal ASCII character set and even the extended ASCII characters). The Touhou games are actually a series that is still in production today though, but now with the games being available for Windows, and will run on any Windows PC, not just PCs sold exclusively in Japan. The original PC-98 Touhou games though were never remade for Windows though, and still require either a real PC-98, or a PC-98 emulator, to run. That's why I was hoping to get PC-98 emulation in DOSBox.

I don't know exactly what its sound system is, but if I remember correctly from some things I've read before, it's different enough from the normal SoundBlaster or Adlib type sound cards for normal PCs, that you'd need separate emulation code for it. I just did some research, and found that the oldest models had only a buzzer (not PC-speaker even, it just had one tone). Next there was a model that did have a PC-speaker, who's frequency was controlled by in interrupt timer. Later there were some models that supported sound cards like the PC-9801-26 sound card. Finally, on the latest models of PC-98 (which actually had an 80286 CPU in them, instead of the older 8086 CPU), they supported a PC-9801-26K soundcard (note the K at the end of the sound card's model number). These latest models usually came with the PC-9801-26K souncard already installed, based on my research. I found this info on the PC-9801-26K sound card:

This includes the Yamaha YM2203 OPN FM synthesizer, providing three 4-operator FM synthesis channels plus the three channels of the integrated YM2149 SSG unit.

I'm not sure what the "YM2149 SSG unit" is. Is it PCM audio? Or did all the soundcards for the PC-98 exclusively support FM synthesis based audio, with no PCM audio? Or was there also PCM audio capability as well? I assume there was PCM audio, as that's the most basic type of digital audio available.

I also read that the latest models of PC-98 also supported the PC-9801-86 soundcard (which had to be manually installed though), which supported 6 FM audio channels (rather than the normal 3), and also offered a few other features (though the source for my info didn't specify what the "few other features" were).

Thank you for a detailed reply. I haven't heard about Touhou games before, so I looked them up on Youtube. All these billions of flying bullets...very impressing.
As for sound, I think it does not show a great deal of variety like PC compatibles. I guess PC-98 was produced only by one company, so should not have many different incompatible with each other sound standards. I assume it had both FM and PCM (perhaps on later models). Still curious about the technical side of things.

Caluser2000 wrote on 2021-05-28, 04:38:

videogamer555 wrote on 2021-05-28, 04:31:

Caluser2000 wrote on 2021-05-28, 04:28:

The 8088 is as 16 bit processor.

8086 is 16bit, while 8088 is 8bit. Both I think have 16bit address lines, but 8088 has 8bit data lines and 8bit registers, while the 8086 has 16bit data lines and 16bit registers.

You are incorrect https://spectrum.ieee.org/tech-history/silico … -microprocessor

By that logic, worlds most famous 8-Bitter, the Z80, must be 16-Bit, too.
It had registers that could hold 16-Bit, as well.
Edit: And it has an 16-Bit address space for memory (64KB).
http://cpmarchives.classiccmp.org/cpm/mirrors … 1/z80_16ld.html

Bondi wrote on 2021-05-30, 16:51:

[..]
As for sound, I think it does not show a great deal of variety like PC compatibles. I guess PC-98 was produced only by one company, so should not have many different incompatible with each other sound standards. I assume it had both FM and PCM (perhaps on later models). Still curious about the technical side of things.

Hi! I've got made a small sound card chart over here.
That being said, I'm afraid the thread is fairly incomplete, still.
What's interesting, the PC-98 platform supported both the CM32L and CM32P.
In fact, having an CM64 is ideal for PC-98. Edit: Or more precisely, the Sharp X68000 platform in particular.
Which may be to no surprise - the Japanese developers made much better use of both PCM and FM than 'us'.
On the other hand, western artists were better in making PSG sound/music perhaps (Tandy 3-Voice, Speaker, Creative CMS, C64 SID, NES).
I'm speaking under correction, but Epson (?) also made some PC-98 compatibles at some point.

Edit: Some parts rewritten.

Thanks, sir! Please have another look at the ad you linked to, though.
It seems there used to be a few other funny people like me. 😉

Edit: Ok, seriously. I think neither of us is really wrong. It's an 8/16-Bit hybrid simply. Or 8/16/20-Bit hybrid, if we include that 20-Bit (1MB) address space.
Some people see the 16-Bit Motorola 68000 as a 32-Bit CPU, also. Hence the "ST" in Atari ST (Sixteen/Thirtytwo).

Jo22 wrote on 2021-05-31, 14:05:

Thanks, sir! Please have another look at the ad you linked to, though. It seems there used to be a few other funny people like m […]
Show full quote

Thanks, sir! Please have another look at the ad you linked to, though.
It seems there used to be a few other funny people like me. 😉

Edit: Ok, seriously. I think neither of us is really wrong. It's an 8/16-Bit hybrid simply. Or 8/16/20-Bit hybrid, if we include that 20-Bit (1MB) address space.
Some people see the 16-Bit Motorola 68000 as a 32-Bit CPU, also. Hence the "ST" in Atari ST (Sixteen/Thirtytwo).

You are veeery wrong. This is what is in my Zenith 80C88 powered laptops user manual:

Intel was emphasising the 8 bittedness of the 8088 externally so as to court system designers who thought 16 bit was scary and who otherwise might have banged out another Z80, or 6800 system.

A bit more out of the manual:

Jo22 wrote on 2021-05-31, 06:05:

Hi! I've got made a small sound card chart over here. That being said, I'm afraid the thread is fairly incomplete, still. What's […]
Show full quote

Hi! I've got made a small sound card chart over here.
That being said, I'm afraid the thread is fairly incomplete, still.
What's interesting, the PC-98 platform supported both the CM32L and CM32P.
In fact, having an CM64 is ideal for PC-98. Edit: Or more precisely, the Sharp X68000 platform in particular.
Which may be to no surprise - the Japanese developers made much better use of both PCM and FM than 'us'.
On the other hand, western artists were better in making PSG sound/music perhaps (Tandy 3-Voice, Speaker, Creative CMS, C64 SID, NES).
I'm speaking under correction, but Epson (?) also made some PC-98 compatibles at some point.

Edit: Some parts rewritten.

Thanks, that seems to be a very interesting thread.
I think I've also seen PC-98 sound cards with MIDI daughterboards attached. So music part is more or less clear. It had both FM and MIDI.
Still not quite sure about PCM, in DOS/v in particular.

Bondi wrote on 2021-06-01, 12:39:

Thanks, that seems to be a very interesting thread. I think I've also seen PC-98 sound cards with MIDI daughterboards attached. […]
Show full quote

Jo22 wrote on 2021-05-31, 06:05:

Hi! I've got made a small sound card chart over here. That being said, I'm afraid the thread is fairly incomplete, still. What's […]
Show full quote

Hi! I've got made a small sound card chart over here.
That being said, I'm afraid the thread is fairly incomplete, still.
What's interesting, the PC-98 platform supported both the CM32L and CM32P.
In fact, having an CM64 is ideal for PC-98. Edit: Or more precisely, the Sharp X68000 platform in particular.
Which may be to no surprise - the Japanese developers made much better use of both PCM and FM than 'us'.
On the other hand, western artists were better in making PSG sound/music perhaps (Tandy 3-Voice, Speaker, Creative CMS, C64 SID, NES).
I'm speaking under correction, but Epson (?) also made some PC-98 compatibles at some point.

Edit: Some parts rewritten.

Thanks, that seems to be a very interesting thread.
I think I've also seen PC-98 sound cards with MIDI daughterboards attached. So music part is more or less clear. It had both FM and MIDI.
Still not quite sure about PCM, in DOS/v in particular.

You're welcome. ^^ Thanks to the other gentleman, I double checked my statements ..
I do admit that I likely made a little mistake, when I was thinking about PCM. And I'd like to apologize for this.
The Sharp X68000 was the one that made good use of CM32L/P.

However, some of the PC-98 games likely also made use of Roland modules at some point (aside from the SC-55?).
Hm. Thing is, information of Japanese stuff is rather hard to get by. Many of the private homepages on the Japanese internet are down or hard to find.
Most of the links that I found directed to the Geocities sites that are now defunct. Maybe some internet archives still have them.
So it's not as easy as browsing Mobygames and check for the specs. Sadly. There are many, many obscure and lesser known games on PC-98..

The DOS/V thing is also a bit confusing. In essence, DOS/V is just an OEM version of PC-DOS (later, MS-DOS) that uses the ability of VGA cards
to install custom fonts (glyphs, see "TUI"). In simple words, the DOS/V machines are bog standard PCs. However, they *may* also have special stuff installed sometimes.
This is comparable to all the "oddware" stuff that used to exist on western PCs, I guess. Like, say, Covox DACs on 16-Bit soundcards (Aztech Sound Galaxy NX Pro) for maximum compatibility.
DOS/V also uses EMM386 do perform some trickery with the memory addresses, I believe. But I must check this, so please don't take that as face value.

The early PC-9800 series PCs had NEC V20/30 CPUs installed at some point. If memory serves, this provided some backwards compatibility with the PC-88 series.
That being said, I don't consider myself an expert. I'm just an user, IMHO. So please see the information more like some sort of brainstorming.

Good luck! :)

The hardest part of emulating PC-98 is probably the graphics and/or sound hardware. Less difficult but still something that would need to be done would be to add features to the DOS (software) side of DosBox (rather than the hardware emulation side). For example, DOS (and possibly the BIOS ROM as well) for PC-98 supported not only normal text in 7 bit ASCII and kana characters (because it was a PC intended for a Japanese customer base) in extended ASCII, it also supported 16bit text to include quite a bit of kanji characters (and the 16bit character codes for these may or may not be the same as the modern Unicode character codes for the characters). This also meant that it needed to have extra character graphics.bitmaps (in other words a Japanese font) in order to display those character. That font would be stored either in DOS itself or in the BIOS ROM (or possibly even in the character ROM chip on the graphics card, which is then itself a unique piece of hardware that would need to be emulated as a separate graphics card, just like CGA, EGA, Tandy, PCJr, etc graphics cards are already emulated by DosBox).

BitWrangler wrote on 2021-05-31, 23:54:

Intel was emphasising the 8 bittedness of the 8088 externally so as to court system designers who thought 16 bit was scary and who otherwise might have banged out another Z80, or 6800 system.

So I was right in that it could only read/write 8 bits of RAM at a time, even if it could internally perform 16bit math operations on the registers. In other words, to load 16 bits into the 8088 CPU you would need to use 2 MOV instructions and a SHL instruction to load a 16bit value from RAM into the register of an 8088 CPU, while the 8086 CPU would be able to load a that same 16bit value with a single MOV instruction. The 8088 code would be:
MOV AL,[DataValueBaseAddress+1] ; Load most significant byte first (goes into least significant byte AL of register AX).
SHL AX,8 ; Shift left 8 bits to put it in most significant byte of the AX register (alternatively you could use "MOV AH,AL").
MOV AL,[DataValueBaseAddress] ; Load least significant byte into register.

The most significant byte of the AX register (called AH) can't be externally accessed by 8088 CPUs.

This entire process is simplified in 8086, where the code is just the one instruction "MOV AX,[DataValueBaseAddress]".

One instruction, in place of 3, significantly increases the operating speed of the CPU by tripling the speed it can copy 16bit values to/from RAM. The more that the program running requires accessing 16bit values from the RAM, the more noticeable this speed boost will be.

It’s also one instruction on 8088, it just takes longer to execute.