A Soundblaster Pro is going to work fine in that machine, if you can fit it mechanically. I don't remember the placement of the battery on the riser card exactly, and if it would interfere with the 16-bit extension of the ISA slot, but I am extremely confident that the Soundblaster Pro uses the 16-bit ISA extension only for access to DMA channel 0 and maybe IRQ 10. The Soundblaster Pro supports no kind of 16-bit bus cycles, so the absence of a 16-bit slot is not going to hurt.

You might want to test the raw video write speed. The V30 should be able to max out the 8MHz ISA bus, which likely runs at the XT rate of 4 clocks per ISA cycle, so the maximum transfer rate is 8MB/s. I don't know about the VGA Wonder, but I tested several VGA cards in my classic Turbo-XT, and none of the (cheap) 8-bit VGA cards was able to sustain 4 clocks per byte write, but an ET4000 and a ATI mach32 ISA were. If you get less than 2MB/s raw write speed, you might want to test a more modern 16-bit VGA card. Contrary to the soundblaster pro, not all 16-bit VGA cards work in 8-bit slots. For example, only two of my three ET4000-based cards worked in my Turbo XT.

Expanding the ISA bus to more slots does not need any logic. But classic TTL chips work in a way that you need to actively draw power from the input pin to make it zero. The mainboard is only able to draw a certain amount of power, so there is an upper limit of TTL chips you may connect to the mainboard until the logic low level gets weak and the system gets unstable. This is much less of an issue if you use expansion cards with modern CMOS-based chips instead of classic expansion cards with TTL chips. The official IBM specification for the ISA bus is "two low-power shottky TTL chips per slot on each ISA signal", and they hit the mainboard limit on the XT. Only seven of the eight ISA slots on the mainboard are directly wired in parallel, whereas the eight slot is driven by a separate logic amplifier (buffer) chip, which needs a special control signal to activate, which is supplied through the reserved ISA bus pin B8. The PS/2 drives the ISA data lines using 74ALS245 chips and the address lines using 74ALS573 chips, which are more modern and definitely strong enough.

The PSU might indeed pose a problem, depending on the load the cards pose on it. You can estimate whether a card "draws a lot of power" by checking whether it gets warm. The Soundblaster 2.0 might take some power for the built-in speaker amplifier. The EMS card might use a considerable amount of power depending on the technology used for the memory chips. 2MB on a half-sized card sound like a modern CMOS-based design, so most likely it is fine, too.

Possible upgrades for that system includ

• a TNDY sound board. As the PS/2 model 30 mainboard does not have the AT-class 16-bit DMA controller, the port range for the tandy sound chip is not claimed by the board. If the board drives addresses below 100h to the ISA bus, you could get tandy compatible sound at the hardware level. The schematics are not helpful for this question, as the decoding process for the "BG L" and "BG H" signals that connect the data lines on the ISA bus to the processor are generated by a custom IBM logic chip, so it is not obvious if they go active for the mainboard I/O range (00h..FFh).
• an MDA/HGC clone card to obtain a dual-monitor system
• a 1.44MB capable floppy controller (but then you need an adapter to connect that controller to a PS/2 floppy drive)

What type of model 30 8086 do you have? I have both a white switch and a red switch version of the model 30 8086. At first i thought it would only be the power switch, and the fact that the one with the red switch uses a 720 kb floppy drive and the one with the white switch uses a 1.44mb drive. But there are a lot more differences between the two models.

The mainboard of the two are completely different.
Red switch version

First the mainboard is about 5 cm longer then the white button version.
The memory simms are located on the front left side of the mainboard.
The rom chips are located on the front left.
The cpu and fpu are located in the middle of the right side of the mainboard.

White switch version

The mainboard is about 5 cm shorter.
The memory simms are located on the right backside near the psu.
The rom chips are located on the middle of the right side of the mainboard.
The cpu and fpu are located on the front left side of the mainboard.

Sadly the 1.44mb drive is dead so i need to replace the caps to see if i can get it working again. But the strangest thing is i can not get the IBM WDL-320 drive working in the red switch version. It detects the harddisk, but it will not boot from it. I checked whit a reference disk so i now the drive detects.
But when putting it in the white switch version, the pc just boots up fine, straight into dos that has been installed on the harddisk. I swapped the cables so i know it isn't a cable issue. I have a full height IBM WDI-325Q that is making horrible sounds when powered up, and is defiantly broken. But i can can low-level format the drive in both model 30 versions without problems (besides the disk sounding like one of the heads crashed.) And before i tried low-level format i could see the disk just fine in fdisk on both machines.

I already cleaned up the red switch version, had a 16bit soundblaster vibra 16 (version with jumpers to set resources) in it working just fine. Also had a xt-ide cf adapter from lo-tech installed. Funny to see a 8086 reporting that it has 1gb of harddisk space. Dir command is really slowed down when the os is calculating the free space.
I also have a model 30 286. This on has the advantage that it has vga onboard instead of the mcga onboard graphics of the 8086 version, so it has EGA support, where as the 8086 version doesn't have it, since it uses an Enhanced version of CGA.
It also comes with 1 mb of ram and of course a faster cpu, making it a more capable machine overall. So i have transferred the soundblaster and cxt-ide cf adapter to this machine for now.

seob wrote on 2021-05-23, 19:03:

Dir command is really slowed down when the os is calculating the free space.

Hi, good evening!

I believe this could be related to how MS-DOS works.
I you're using FASTOPEN and/or a NEC V30 CPU, DIR should work a bit quicker..

A "DIR marathon" of different DOSes would be fun, IMHO! 😉

Edit: This might be also interesting..
"The performance increase of the 80286 over the 8086 (or 8088) could be more than
100% per clock cycle in many programs (i.e., a doubled performance at the same clock speed).
This was a large increase, fully comparable to the speed improvements around a decade later
when the i486 (1989) or the original Pentium (1993) were introduced.

This was partly due to the non-multiplexed address and data buses, but mainly to the fact that
address calculations (such as base+index) were less expensive.
They were performed by a dedicated unit in the 80286,
while the older 8086 had to do effective address computation using its general ALU,
consuming several extra clock cycles in many cases.

Also, the 80286 was more efficient in the prefetch of instructions, buffering,
execution of jumps, and in complex microcoded numerical operations such as
MUL/DIV than its predecessor.[12]"

Source: https://en.wikipedia.org/wiki/Intel_80286

Maybe this is one of the reasons the old 8086 was so slow in many cases?
808x is the only x86 CPU which is forced to perform such complex calculations via its little ALU.

Edit: Fixed the formatting.