SilverStone ALTA G1M Micro-ATX Case Review

Manufacturer: SilverStone SilverStone ALTA G1M Micro-ATX Case Review

SilverStone’s ALTA G1M is a recently-released small-footprint Micro-ATX enclosure that features the company’s “stack effect” thermal design, which we explored with the compact LD03 last year. It has a footprint of just 7.87″ (W) x 12.09″ (D), but manages a 31.1 liter volume thanks to its 19.96″ height.

As with the Fortress FT03 before it, this case is built around a motherboard that is rotated 90 degrees, and the stack effect begins with a 180 mm “Air Penetrator” bottom intake fan, with warm air exhausted from the top. Unlike the FT03 before it, the ALTA G1M offers double and triple-width radiator support up to 360 mm.

The case is available in black (SST-ALG1MB), as reviewed, or white (SST-ALG1MW). It carries a list price of $169 USD – though it is already selling for a bit less, with a $152.45 price tag on Amazon as I write this.

SilverStone ALTA G1M System
Product Specifications
  • Model Number: SST-ALG1MB (Black), SST-ALG1MW (White)
  • Material: Plastic, steel
  • Motherboard Support: Micro-ATX (9.6″ x 9.6″), Mini-ITX (6.7″ x 6.7″)
  • Power Supply Support: SFX, SFX-L
  • Expansion slots: 4
  • Drive bays, Internal: 2,5″ or 3,5″ x 4 (without installing fans / radiator)
  • Cooling System
    • Fan Support:
      • Rear: 120mm x 2 (without installing 2.5″ or 3.5″ drives)
      • Side: 120mm x 3 (without installing 2.5″ or 3.5″ drives)
      • Bottom: 180mm x 1 (180mm x 1 Air Penetrator fan included)
    • Radiator Support:
      • Side: 360mm / 240mm / 120mm
  • Front I/O ports: USB Type-C x 1, USB 3.0 x 2, Combo audio x 1
  • Component Clearance:
    • Limitation of VGA card: Length 355mm, Width 165mm
    • Limitation of CPU cooler: 159mm (without installing side fans / radiator)
    • Limitation of PSU: 130mm
  • Net weight: 6 kg / 13.2 lbs
  • Dimension: 200mm (W) x 507mm (H) x 307mm (D) / 7.87″ (W) x 19.96″ (H) x 12.09″ (D), 31.1 Liters
$169.99 USD List
Manufacturer Description

“Embodying the characteristics & qualities of the iconic Fortress FT03, ALTA G1M features a 90-degree rotated motherboard layout and a small overall footprint that’s tall in height but short on depth.”

The SilverStone ALTA G1M Case

SilverStone ALTA G1M Case Front Angle

We are looking at a monolithic design, standing tall but taking up very little space with a footprint of just under 8 inches wide and depth of about 12 inches. With a height of 20 inches the overall verdict is that this is not bigger than a bread box, as long as yours supports longer loaves and you keep it on its side (bread box reviews in the future?).

Three of the sides are generously vented, and one side is a solid steel panel. This case does not offer a window, and that is probably for the best considering how poorly I managed cables in my build (more on this in a bit).

Both the top and bottom of the case are interesting, as the top is actually home to the usual rear connections due to that 90-degree motherboard rotation, and the bottom features a large intake via the space between the plastic base and the bottom of the enclosure itself.

Build Notes

The ALTA G1M build begins with the removal of the fan/storage bracket above the component chamber, and I won’t have too much to say about it as the process was smooth thanks to the generous interior (particularly if you opt for a mini-ITX board as I did). There are large openings for cable routing, and a reasonable amount of space behind the motherboard tray to organize cables.

As mentioned, just like the Fortress cases this features a 90-degree rotated motherboard layout, wherein the GPU hangs from the top of the case like a bat, suspended above the massive 180 mm intake fan on the floor. I will note that support for long graphics cards (listed at up to 355 mm) may require better component selection than I had. A long-winded explanation follows.

I started with an RTX 3080 Ti FE card along with a Strix B450-I board, and there were zero clearance issues. Then, after some mysterious boot problems that prompted me to swap components after a protracted struggle and a lot of profanity, I ended up with a mini-ITX Intel Z390 board. None of this is very interesting, except that after the board swap, suddenly the card’s cooler, which extends over the metal protruding slightly below the motherboard tray, was making contact with the case. Maybe it was just me.

SilverStone ALTA G1M Case Front Angle

You can see the area in the photo above. With the 3080 Ti FE card I felt resistance when securing the card in the PCIe slot because of the contact back there – though it clearly came down to the motherboard I used. A micro-ATX board, or a board with a slightly thicker PCB, would have posed no issue in this regard. Needless to say I gave up and used a shorter card to finish the review.

After installing motherboard and GPU I unpacked the 360 AiO cooler and got to work mounting this with the case’s front fan bracket. Initially, the nest of wires was obscene – though some rough bundling with twist ties allowed me to close up the case without issue.

After securing the fan mount – which attaches with two metal tabs at the base and two screws at the top – the AiO cooler was installed and the build was basically done. Here’s a look at the mostly finished build, taken before installing the fan bracket:

SilverStone ALTA G1M Case Build in Progress

If you look closely at this photo you can just make out the holes on the right side, opposite the GPU, for mounting storage drives

And now a look at the completed build, which features a rather pedestrian Radeon RX 6600 XT (the closest shorter card to me at the time) and a quaint 9th Gen Intel Core i9-9900K CPU – because for some reason I have no mini-ITX boards newer than Z390.

Please excuse the slight bulge to the front panel in this photos – I had not snapped it back in place correctly. I want to add that I was surprised that installation of the largest cooler this case supports went as well as it did, and there was just enough room to keep the hoses from being stressed. Of course I could have mounted the cooler with the fans behind the rad, rather than against the side of the case, and probably should have (more on this later).

I was quite impressed with the attention to detail from SilverStone regarding the case exterior. With the build finished the top I/O can easily be routed out the back, and not only is there a handy clip for your display cable and whatever other cabling you might have, but the rear opening has a rubber grommet.

The finishing touch is the centered, recessed power connector on the bottom rear of the case. The SFX-L power supply is installed just above this, but to keep things looking neat from the front the cable is routed via a short extension to this location, and it’s a very nice design.

With the system together it was time to run some thermal and noise tests.

Thermals and Noise

I dread this part of the process, as every component swap negates all previous test results with other cases. Suffice it to say, thermals were fine – though I was reminded why running an Intel Core i9-9900K with no limits (the default for even the mITX Gigabyte Z390 I AORUS PRO board it was installed in) is such a bad idea when I hit 100 C under all-core loads before optimizing fan/pump speeds. The GPU was a simple (yet still unobtainable) AMD Radeon RX 6600 XT – the MSI GAMING X version from our review, run stock.

After going into system setup and manually entering the actual Intel power limits for the Core i9-9900K (95W PL1, 118W PL2, 8s Tau) I simulated a gaming session by running Unigine Heaven for 45 minutes. I compared the results inside the case vs. the same components on the open test bench in a separate 45-min run, and the results included a small rise in GPU temp inside the ALTA G1M – from 38.6 C to 41.4 C, delta – while CPU temps rose considerably – from 32.6 C to 45.4 C, delta.

SilverStone ALTA G1M Case Build in Progress

Plenty of air enters via the lower vent, which feeds the bottom-mounted 180 mm intake fan

This 12.8 C rise from open test bench to enclosure with the same CPU cooler caused me to again question placing the AiO cooler’s three 120 mm fans up against the vents, since I was probably reducing airflow. The hissing sound during loads from the vent holes told me that air was entering, but there was quite a bit of resistance. So, don’t do that. There is clearance to mount such a cooler and fans either way. Honestly, a big air cooler, with help from the 180 mm Air Penetrator fan down below and vents above, would be my choice for the CPU in this case.

As to noise levels, these will vary by component selection, obviously, and with my haphazard little build I measured, as built with 360 AiO, “normal” motherboard fan profiles, and a full speed AiO pump, some 32.4 dBA at idle and 39.3 dBA under load. Again I was reminded of my mistake in mounting the fans on the outside of the radiator, as the fans drawing in air directly through the vents at such close range produced quite a pronounced hissing sound.

I will add that my concerns about noise levels from the Air Penetrator fan were unfounded. I guess I remember running the three at the bottom of my Fortress FT02 at 100%, since I was over-volting and overclocking my two air-cooled Radeon 5870 GPUs back then. It was well behaved here.

Final Thoughts

The SilverStone ALTA G1M is an interesting case, providing a unique vertical take on an mATX design with the small footprint of a mITX case. Like the Fortress FT03 case it is so closely related to, it is quite tall for this form-factor, and because of this it’s pretty impressive just how much can be crammed into this footprint thanks to the rotated layout and 360 mm rad support. That radiator support does come at a price, however, as the bracket is shared with half of the case’s storage support (the rest is along the wall opposite the GPU).

SilverStone ALTA G1M FT03 Photo

SilverStone’s ALTA G1M promo image shows its close relative, framed, on the wall

The SFX/SFX-L power supply requirement also reduces the flexibility of this design compared to a case like the SUGO 15 (reviewed here back in May), which is my pick for the better small form-factor option from SilverStone if you’re OK with a (far more common) mITX motherboard. Still, if you prefer the flexibility of a micro-ATX board over mini-ITX, and are OK spending a little more on an SFX-L power supply, the ALTA G1M might be the better option.

The overall quality of the ALTA G1M case is quite high, and offers a mix of features I don’t think you’ll find elsewhere. However, the list price of $169 (currently down to $152), gives me pause when I think back to the outstanding – and aluminum clad – SUGO 15, though the latter has crept up some $20 since my review and is now selling for $197 – a 25% bigger investment than the ALTA G1M. Still, if desk space is at a premium the ALTA G1M offers a very polished experience, right down to external cable management, and it has an understated aesthetic that I like quite a bit.

PC Perspective Silver Award

Review Disclosures

This is what we consider the responsible disclosure of our review policies and procedures.

How Product Was Obtained

The product is on loan from SilverStone for the purpose of this review.

What Happens To Product After Review

The product remains the property of SilverStone but is on extended loan for future testing and product comparisons.

Company Involvement

SilverStone had no control over the content of the review and was not consulted prior to publication.

PC Perspective Compensation

Neither PC Perspective nor any of its staff were paid or compensated in any way by SilverStone for this review.

Advertising Disclosure

SilverStone has not purchased advertising at PC Perspective during the past twelve months.

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About The Author

Sebastian Peak

Editor-in-Chief at PC Perspective. Writer of computer stuff, vintage PC nerd, and full-time dad. Still in search of the perfect smartphone. In his nonexistent spare time Sebastian's hobbies include hi-fi audio, guitars, and road bikes. Currently investigating time travel.


  1. BigTed

    Looks nice aesthetically, but I never like having a pony tail of cables hanging out the top of the rear. Anyway, what am I talking about – my ideas of cable management is shouting at the wife to tighten the thumb screws as I hold the bulging side panel flush.

  2. Leftover turkey

    Thanks for the review. Since I place my cases on my (rather compact) desk, I prefer tall cases with a small footprint. Even a few inches difference is important space saved for other items.

    I’ve always gravitated towards Silverstone and Lian Li chassis for a number of reasons, and this Alta g1m looks right up my alley. I need at least 1x 3.5” hdd and 2x ssd, so I’ll probably equip a beefy air cooler for the cpu, and an aftermarket cooler gpu that vents into the case. That cooling scheme is similar to imo the best config for running the author’s old Silverstone Fortress/Raven 02 designs. Maximize the bottom-up cooling and those kickass 180mm Penetrator fans versus disturbing airflow with a side-mounted radiator.

  3. brain

    Looks nice… I miss the older Lian Li cases, especially the PC-V1000 series. Nothing like thicker aluminum.
    If anyone has any similar suggestions to the PC-V1000 series I’m all ears!

  4. Quentin

    I used to be a big fan of rotated cases – I have both a FT02 and a FT05 – but they simply don’t work over the long term with modern GPUs. The heatpipes go the wrong ways. You need a GPU with a blower fan or one that’s part of a custom loop. My FT05 is now on its side.

    I don’t understand why you’re forcing AIO cooling on this case. The rotated cases have always been about air cooling. Or a custom loop.


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