At a distance of just 11.2 Mly, IC 342 represents one of the closest massive spirals beyond the Local Group, exhibiting the abundance of star-forming activity at low inclination – almost face on (i ~ 30°).
This H-α LRGB image was obtained with the A1 telescope installed at the Alnitak Remote Observatory in Nerpio, Spain:
Acquisition software: DC-3 ACP, MaximDL Pro, TheSky X
Processing software: DeepSkyStacker, PixInsight, RC Astro BlurXTerminator, NoiseXTerminator, StarXTerminator, GraXpert, GIMP.
Young stars in galaxies are usually grouped together. These groups may come in a variety of sizes – from relatively small parsec-sized open clusters to very large OB complexes spanning about a thousand of pc. NGC 206 is the richest OB stellar association located in the outer disk of the Andromeda galaxy, M31. Given the proximity of Andromeda and the abundance of massive stars in the association, NGC 206 provides us with a unique laboratory to study stellar formation at the high end of mass spectrum, above 20 M☉. While earlier publications have referred to it as an OB complex due its size (850 pc), later publications call it an OB association primarily due to that it appears to represent a single region where a star formation episode has taken place.
Simulations reveal NGC 206 represents such a large overdensity in the Andromeda galaxy’s disk that it affects it gravitationally, playing a decisive role in the formation of Andromeda’s dust lanes (Mohr 1997; 1998). The age of the NGC 206 association is estimated to be about 20–30 Myr (Brinks 1981, Magnier et al. 1997). It hosts so many massive young stars, including Wolf-Rayet stars and supergiants, that it has carved out a hole, about 800 x 400 pc in size, in the surrounding Andromeda’s neutral hydrogen gas (Hunter et al. 1996). Brinks (1981) has even titled his paper as “a hole in M31.” Similar H I holes, produced by stellar winds and supernovae from hot young stars, have been found in our Galaxy and the Large Magellanic Cloud (LMC). It is estimated that in NGC 206, out of 2 × 106 M☉ of the original Andromeda’s H I gas in the area, ~ 10% has been used to form the stars, ~ 25% was ionized and the rest has been blown away. The hole also coincides with low surface brightness H-α emission.
NGC 206 is located in the southern disc of M31, in the area most likely disturbed by the past encounter with its satellite galaxy, a compact elliptical M32 (Kavanagh et al. 2020). This could explain the trigger for the formation of such a large stellar association in Andromeda – an off-center passage of M32 through the disk could also explain the presently observed Andromeda’s ring structure. The exact timing of the encounter is still being debated – some earlier models have put it at ~ 200 Myr ago, albeit having troubles explaining present position of the M 32, while newer models suggest it may have been a much older event – 800 Myr ago (Dierickx et al. 2018). In all cases, the encounter seems to precede the estimated age of the NGC 206 by at least a factor of 10. Was the OB association formed by dynamical disturbances long after the M32 encounter, and if so, what was the reason for such a delay?
A study by Magnier et al. (1997) suggests that as NGC 206 is located at the intersection of two spiral arms of Andromeda it is the interaction between the arms that is responsible for the stellar formation in this association. Could the M32 encounter event have resulted in multiple star-forming events at the site? Could those interactions represent reverberations of the initial gravitational disturbance from the passage – is there any link at all?
In the recent study of the superbubble associated with the giant 465 pc-sized H II region Henize 206 in the LMC by Ramachandran et al. (2018) the ages of OB stars reveal a large spread – from 1 to 30 Myr – suggesting that area has experienced multiple episodes of star formation. It appears OB associations within this complex were formed at different times, albeit that has occurred on a time scale still much shorter to be directly comparable with the M 32 passage time scale. It is interesting that galaxy mergers were recently shown to have little impact on star formation rates (Pearson et al. 2019) or they can even quench stellar formation in the galaxy quite rapidly due to energetic feedback processes (Ellison et al. 2022). An off-center collision of M31 with M32, however, may have produced a completely different effect than a merger. Models suggest this event was responsible for the Andromeda’s star-forming pseudo-ring structure, easily detectable through our telescopes in H-α light.
This H-α RGB image was obtained with the A1 telescope installed at the Alnitak Remote Observatory in Nerpio, Spain:
Acquisition software: DC-3 ACP, MaximDL Pro, TheSky X
Processing software: DeepSkyStacker, PixInsight, RC Astro BlurXTerminator and NoiseXTerminator, GIMP, StarNet.
OTHER AREAS OF INTEREST
Some of the brightest H II emission regions are shown below, along with their SIMBAD references.
Many of the open clusters are present in the catalogye by Hodge (1979) who has studied 403 open star clusters in M31 on 29 B channel plates obtained with the Kitt Peak National Observatory 4-m telescope. The three Hodge open clusters shown below are also OB associations specified in the Hill-Isensee-Bohlin+ [HIB95] catalog. The Hodge B-179 open cluster is known as the [HIB95] 22-5 OB association, and B-154 is AKA [HIB95] 132-3. The Hodge B-107 is a 15.5 V magnitude small and round open cluster in a dense field of young blue stars. It is AKA [HIB95] 80-8.
The Pellet-Astier-Viale+ 228 emission object appears with the Azimlu-Marciniak-Barmby [AMB2011] HII 480 ionized hydrogen region and Helga 308 molecular cloud on the top of the emission ring.
The Massey-Armandroff-Conti OB 69-F1 is a Wolf-Rayet (WR) star of the WC6–WC7 spectral type. There is a study of H II shells around WR stars in the Andromeda galaxy by Bransford et al. (1999). WR stars are known to form dust shells. I wonder if the dark ring surrounding the star in this image is a dust shell superimposed over H II emission in the background.
REFERENCES
Bransford, M. A., Thilker, D. A., Walterbos, R. A. M., King, N. L. 1999, AJ, 118, 1635
Brinks, E. 1981, A&A, 95L, 1B
Dierickx, M., Blecha, L., Loeb, A. 2018, ApJL, 788, 38
Ellison, S. L., Wilkinson, S., Woo, J., et al. 2022, MNRAS, 517, 92
Hodge, P. W. 1979, AJ, 84, 744
Hunter, D. A., Baum, W. A., O’Neil, E. J., Jr., Lynds, R. 1996, ApJ, 468, 633
Kavanagh, P. J., Sasaki, M., Breitschwerdt, D., et al. 2020, A&A, 637, A12
Magnier, E. A., Prins, S., Augusteikn, T., et al. 1996, A&A, 326, 442
Mohr, R. 1997, BAAS, 29, 1380
Mohr, R. 1998, BAAS, 30, 1407
Odewahn, S. 1987, AJ, 93, 310
Pearson, W. J., Wang, L., Alpaslan, M., et al. 2019, A&A, 631, A51
Ramachandran, V., Hamann, W.-R., Hainich, R., et al. 2018, A&A, 615, A40
NGC 6960, also known as the Witch’s Broom, is part of the Veil Supernova Remnant in Cygnus, at a distance of 2,400 ly from Earth.
This narrowband image is captured in the SHO Hubble palette, with [S II], H-alpha and [O III] emission assigned to RGB channels respectively. It was obtained with the A1 telescope installed at the Alnitak Remote Observatory in Nerpio, Spain:
Acquisition software: DC-3 ACP, MaximDL Pro, TheSky X
Processing software: DeepSkyStacker, PixInsight, RC Astro BlurXTerminator and NoiseXTerminator, GIMP.
Sharpless 2-88 (LDN 139) Nebula
Also known as the Face of God Nebula, Sharpless 2-88 lies in the constellation of Vulpecula at a distance of 6,523 ly from Earth. It is part of the Vulpecula OB1 association. M. Schuster provides a comprehensive overview of the region.
This narrowband image is captured in the SHO Hubble palette, with [S II], H-alpha and [O III] emission assigned to RGB channels respectively. It was obtained with the A1 telescope installed at the Alnitak Remote Observatory in Nerpio, Spain:
Acquisition software: DC-3 ACP, MaximDL Pro, TheSky X
Processing software: DeepSkyStacker, PixInsight, RC Astro BlurXTerminator and NoiseXTerminator, GIMP.
The NGC 6823, in the center of this image, is a young galactic star cluser located at a distance of about 6,500 ly from Earth. It is classified as Trumpler IV 3p and is surrounded by the ionized hydrogen region Sharpless 2-86, which it excites with ultraviolet radiation coming from its young O and B-type stars. The cluster has a trapezium of bright stars in its center (Stone 1988).
Almost half a decade of studies of this area of the sky have identified a large population of young stellar objects (YSOs), such as pre-main sequence δ Scuti and UX Ori variables, T Tauri and Herbig Ae/Be stars (Lata et al. 2023) which are on their way to evolve to main sequence stars. The star cluster itself was formed about 3 myr ago and comprises the core of the Vulpecula OB1 stellar association – a giant molecular cloud located in the Local Spur – a layer of stars between the Local and Saggittarius Arms of our Galaxy (Billot et al. 2010). Many of the stars in the corona of the cluster appear to be only 0.5 Myr old, suggesting that the cluster had two distinct episodes of stellar formation (Stone 1988).
Dark molecular hydrogen pillars seen here are reminiscent of the famous Pillars of Creation of the Hubble’s Messier 16 nebula image. These pillars are often associated with the recent episodes of stellar formation, as they are formed due to the sculpting of material by radiation and energetic stellar winds (flow of gases) emanating from very young stars. The external pressure at the surface of these pillars is known to trigger further stellar formation. Many dark globules can be seen throughout the frame, some embedding YSOs.
The episodes of stellart formation could have been triggered by the cloud-cloud collision within the Vul OB1 molecular cloud (Kohno et al. 2022). Another trigger for a more recent stellar formation activity in the region could be the shockflows coming from the supernova associated with the remnant SNR G59.5+0.1 located outside of this frame, which is about 86,000 yr of age. YSOs that formed as little as 105→6 yr ago have been identified (Xu & Wang 2012, 2013) in the region, likely formed due to the collapse of the material in the molecular cloud. In particular, the expanding shell of SNR G59.5+0.1 is pressing against the Sh 2-86 H II region, with two arcs containing high density of YSOs identified around the supernova remnant.
At the top right of the frame, another nebula could be seen – NGC 6820, of which there are not many references available. Bronfman et al. (1996) identify it as an ultra-compact H II region. This site is also the source of methanol maser emission at 44 GHz, associated with the formation of high-mass stars (Litovchenko et al. 2011). Judging by the color matching nearby stars, the NGC 6820 nebula appears to have a predominant reflection component, as ionized hydrogen emission would be expected in green.
This narrowband image is captured in the SHO Hubble palette, with [S II], H-alpha and [O III] emission assigned to RGB channels respectively. It was obtained with the A1 telescope installed at the Alnitak Remote Observatory in Nerpio, Spain:
Processing software used: ACP DC-3, MaximDL Pro, TheSky X, DeepSkyStacker, PixInsight, RC Astro BlurXTerminator and NoiseXTerminator, GIMP.
REFERENCES
Billot, N., Noriega-Crespo, A., Carey, S., et al. 2010, ApJ, 712, 797
Bronfman, L., Nyman, L.-A., May, J. 1996, A&AS, 115, 81
Lata, S., Chen, W. P., Pandey, J. C., et al. 2023, MNRAS, 520, 1092
Litovchenko, I. D., Alakoz, A. V., Val’Tts, I. E., Larionov, G. M. 2011, ARep, 55, 1086
Kohno, M., Nishimura, A., Fujita, S., et al. 2022, PASJ, 74, 24
Stone, R. C. 1988, AJ, 86, 1389
Xu, J.-L., Wang, J.-J. 2012, A&A, 543, 24
Xu, J.-L., Wang, J.-J. 2013, IAUS, 292, 63
Messier 101 (M101), also known as the Pinwheel Galaxy, is a grand design spiral galaxy in the constellation of Ursa Major. Located nearby – just 23 Mly away from Earth, it is one of the largest galaxies in the sky. It is difficult to observe visually in any detail due to its low surface brightness, and generally requires a very dark sky to enjoy, even with NV devices. Being the brightest member of a loose galaxy group called the “M101 Group”, it is also one of the most well-studied galaxies in the sky. It provides a “unique laboratory” for studying the evolution of spiral galaxies that undergo tidal interactions (Linden et al. 2022).
The obvious asymmetrical morphology of M101 points to its violent past. One model suggests that approximately 200 Myr ago, a companion galaxy, NGC 5474, which also part of the M101 group, has grazed the M101’s outer disk, approaching within only ~ 10 kpc, triggering a strong gravitational response and disrupting the dynamical equilibrium of the galaxy. This explains the overall lop-sidedness of M101, its ~ 30 kpc-long North-East Plume, extending far beyond the image frame towards down-left, and the sharp western edge of the galaxy (Linden & Mihos 2022).
What is somewhat unexpected is that there are no obvious tidal tails that connect M101 to any of the smaller galaxies in the group that would point to a recent interaction. If the grazing encounter model is correct, M101 is currently in the state of a recovery from this collision, while the disruptor, NGC 5474, continues to move away on a loosely bound orbit. The disrupted material in M101 continues to mix azimuthally, and the NE Plume is falling back onto the galaxy, forming a distinct stellar stream.
Despite being one of the most visited galaxies by the astrophotographic community, M101 is quite a rare phenomenon in the Local Universe, in the sense of its large, > 5 magniude gap in the luminosity distribution of its satellite galaxies, which is supposed to be more uniform. This presents a challenge to the known models of galaxy formation. Recent simulations show that this configuration can still fit the standard LambdaCDM cosmological model, although only about 1 out of 1000 galaxies formed will display such a magnitude gap with its satellites. The gap itself can be explained by the recent accretion of bright satellite galaxies and is expected to be temporal, disappearing on timescales of a few Gyr (Zhang et al. 2021).
According to de Vacouleurs et al. (1991) – the morphological reference used in the NASA NED – M101 is of SAB(rs)cd morphological type, which signifies an intermediate, weak-bar spiral between normal and barred spirals, with a transitional subtype indicating the presence of weak ring-like structure. I am uncertain why a transitional (rs) designation was assigned, as spiral arms can be traced all the way to the center and it is difficult to find a pseudoring such as in, e.g., IC 239. HyperLeda database specifies a different SABc type based on a more recent reference. Both types are continued to be used throughout the recent literature.
This image was obtained with the A1 telescope installed at Alnitak Remote Observatories in Nerpio, Spain:
Processing software used: ACP DC-3, MaximDL Pro, TheSky X, DeepSkyStacker, PixInsight, RC Astro BlurXTerminator and NoiseXTerminator, GIMP.
REFERENCES
de Vacouleurs, G., de Vacouleurs, A., Corwin, H. G. Jr., et al. 1991, in Third Reference Catalogue of Bright Galaxies, Springer, New York, NY
Linden, S.T., Mihos, C. J. 2022, ApJ, 933, 33
Linden, S. T., Perez, G., Calzetti, D., et al. 2002, ApJ, 935, 166
Zhang, D., Luo, Y., Kang, X., Qu, H. 2001, MNRAS, 508, 1555
Messier 86 (M86, NGC 4406) is one of the most prominent elliptical galaxies in the Virgo Cluster of galaxies, located relatively nearby – just 55.6 Mly away from Earth, appearing quite bright at magnitude 8.9. It can be spotted in telescopes of moderate sizes at dark sky locations, and usually is not imaged too often by advanced astrophotographers, as it is considered somewhat featureless, especially when compared to grand spirals like the Whirlpool Galaxy, or the myriads of astonishing, complex emission nebulae of the Milky Way.
One interesting aspect of the M86, however, is that it shows a negative redshift (blueshift) of z = – 0.001, with its heliocentric radial velocity measured at -302 km s-1. In other words, the M86 is moving towards Earth, as opposed to the majority of other galaxies which are redshifted and are receding away from us due to the so called Hubble Flow – the expansion of the universe. Out of approximately a million galaxies with measured redshifts, only about a hundred are blueshifted like M86, so this situation is quite rare (Karachentsev & Nasonova 2010).
The blueshift of M86, along with its satellites, is explained by the “infall” of these galaxies towards the center of the Virgo Cluster. The M86 is estimated to pass through the core of the cluster approximately every 5 Gyr (Elmegreen et al. 2000). This local gravitational “dance” of galaxies within the cluster makes M86 move towards Earth “from behind” the cluster’s center, as seen from Earth, at the velocity greater than the Hubble Flow, hence the blueshift (Böhringer et al. 1997).
On its journey through the cluster, the M86 appears to be traveling supersonically, at the velocity of approximately Mach 2 (Ehlert et al. 2013). As it is located within about a hundred kiloparsecs to nearby galaxies, it is experiencing ram pressure stripping as it plunges into the intracluster medium (ICM). This intergalactic “wind” the M86 and other galaxies experience within the cluster environment effectively strips their material, so this phenomenon is common in galaxy clusters.
The faint wisps of dust visible in this image overlaying the optical halo of M86 actually belong to the M86 galaxy itself, or at least they are located in the Virgo Cluster and are not part of the foreground medium. They are coincident with the structure called M86-SE detected at far infrared wavelength using the SPIRE imaging spectrometer on board the ESA’s Herschel Space Observatory (Gomez et al. 2010), and, also, optical SDSS absorption features called “A” and “B” in the paper by Elmegreen et al. (2000). According to one interpretation these dust streamers could have been ram pressure-stripped from the dwarf galaxy VCC 882 (PGC 40659 in the annotated image linked below), prominent just north of the M86’s brightest region in this image, when this dwarf passed through the M86. Another interpretation is that they could have been stripped from NGC 4438 – one of the “Eyes Galaxies” of the Markarian’s Chain, located just outside this image.
Messier 86 Full Scale Image (2560 x 1720 pixels)
This LRGB image was obtained with the A1 telescope installed at Alnitak Remote Observatories in Nerpio, Spain:
Software used ACP DC3, MaximDL Pro, TheSky X, DeepSkyStacker, PixInsight and GIMP.
A Quasar in Unreachable Universe
The maximum redshift object in this image, according to the NASA/IPAC Extragalactic Database (NED), is WISEA J122544.87+130636.3 at z = 4.35:
This corresponds to the light travel time of 12.326 Gyr and the comoving radial distance of 24.719 Gly. Assuming this is a quasar and the z measurement is correct, this puts this object into the early universe – the Era of Quasars which peaked at about z ~ 2.2, among the first active galactic nuclei. This portion of the universe is completely and forever unreachable for us, by rockets or signals, as these galaxies are now receding from us faster than the speed of light (Gott et al. 2005).
Globular Clusters
Plenty of M86’s globular clusters are visible, identified in the Subaru Spectroscopy of the Globular Clusters in the Virgo Giant Elliptical Galaxy M86 by Hong Soo et al. (2012) and other sources:
Globular clusters also appear detectable in the nearby galaxy NGC 4402 which appears to the left of M86 in the original image:
REFERENCES
Böhringer, H., Neumann, D., Schindler, S. 1997, ApJ, 485, 439
Elmegreen, D., Elmegreen, B., Chromey, F., Fine, M. 2000, ApJ, 120, 733
Ehlert, S., Werner, N., Simionescu, A. et al. 2013, MNRAS, 430, 2401
Hong Soo, P., Myung Gyoon, L., Ho Seong, H. 2012, ApJ, 757, 184
Gomez, H., Baes, M., Cortese, L. et al. 2018, A&A, 518, L45
Gott, J., Jurić, M., Schlegel, D. et al. 2005, ApJ, 624, 463
Karachentsev, I., Nasonova, O. 2010, Astrophysics, 53, 1
Annotated Image:
PlaneWave Instruments CDK17
Moravian C3-61000 Pro
Software Bisque Paramount ME GEM
Chroma B · Chroma G · Chroma R · Chroma L
FLI CenterLine CL-1-14 Filter Wheel · Optec Sagitta Off-Axis Guider
DC-3 Dreams Advanced Observatory Software ACP Observatory Control Software · Diffraction Limited MaxIm DL · Pleiades Astrophoto PixInsight · Software Bisque TheSky
ZWO ASI174MM
Chroma B: 30×60″(30′) -20°C bin 2×2
Chroma G: 30×60″(30′) -20°C bin 2×2
Chroma L: 30×60″(30′) -20°C bin 2×2
Chroma R: 30×60″(30′) -20°C bin 2×2
Integration: 2h
Pixel scale: 0.703 arcsec/pixel
Locations: Sierra del Segura, Spain, Nerpio, CM, Spain
My 2022-2023 research together with Jeremy Shears, Director of the British Astronomical Association, Variable Star Section.
During the British Astronomical Association (BAA) 2022 campaign, 27,436 photometric observations of the dwarf nova (DN) CG Draconis were made, with 106 eclipses recorded. This work summarizes the new data available and provides updated ephemeris and commentary on the observed eclipse profiles. The orbital period found is . Two types of quasi-periodic outbursts are identified: normal outbursts, of mag amplitude, and bright, of mag. The pattern resembles superoutbursts of SU UMa-type DNe, however, no presence of superhumps characterizing these DNe was found. Given CG Dra is located above the period gap, it may represent a new intermediary subtype between SS Cyg and SU UMa-type stars, or provide support to superoutburst models that do not rely on eccentric accretion disks.
Original article: https://onlinelibrary.wiley.com/journal/15213994
]]>What is the most simple computer? The idea was to learn electronic circuit design by building a minimalist computer using a classic 8-bit microprocessor. For those of us who started computing with the Sinclair ZX Spectrum 48k and its hundreds of clones, what processor could be more suitable for this task than the legendary Zilog Z80? This design is inspired by Steve Rayner’s Z80 build, Ben Eater’s 6502 computer, the original ZX schematics, and a box of components I have got on Amazon.
SAM stands for the Slowest Assembly Machine or a Simple Assembly Machine (or maybe Smooth As Molasses.) The Z80A CPU clock is provided by the 74HC214 Schmitt Trigger with an RC circuit, which is a simple oscillator. Its frequency is given by f = 0.8/RC, so the computer runs at 0.8 Hz and can turbo to a whopping 80 kHz and beyond if you change capacitors. The clock can be stopped with a switch, giving the ability to pause execution, which is handy for debugging purposes.
An array of eight DIP switches is used as the input directly into the data bus of the processor, and LEDs as the output. The first test implementation had no RAM, so simply locking the input to, say, all zeroes, executes a series of assembly “no operation” instructions (NOPs), or 11000011 (equals to C3h) for a series of unconditional jumps (JP) to the same address, because the opcode for the JP instruction is C3h. This was the first 3-byte “program” I’ve got running on SAM-0 with zero memory:
JP C3C3h
The reset circuit has a time delay implemented via 100 µF capacitor and 100 kΩ resistor, suspending the CPU in reset state for a brief moment of time after the power-on and when the Reset switch is pressed.
Where does an abacus end and computer begins? Anything programmable I would consider a computer, so it really needs memory. The SAM-80 design features two 4-bit 5114 Static RAM chips that do not require clock input or refreshing like DRAM chips, keeping things simple. Because of the 8-bit address bus, only 256 bytes are addressable, but this can be expanded.
The 74LS245 chip serves as a bus transceiver when CPU needs to address the RAM. It is enabled by the Memory Request signal of the CPU. When enabled, the CPU can transmit the requested memory address via the address bus to memory chips to read or write stuff. By default the 74HC14 inverting trigger generates a clean “read” signal to the RAM at all times, unless CPU intends to write to RAM or an operator pushes the Memory Commit button to write to memory manually. The RAM chips are always powered on and selected, so even if the Reset button is pressed, memory contents remain intact and the processor begins execution from address 0.
That’s about it – a simple programmable machine, fully capable of executing Z80 Assembler, perhaps very similar to a Kenbak-1. The SAM-1 name was taken by some Norwegian Defence Research Establishment in the 60s, so this one proudly displays the number 80.
The very first program executed from memory was the read-write test:
LD A, 111110b
LD (111110b), A
HALT
This program occupies 6 bytes of memory. It loads the number 111110b (binary) into CPU register A and then loads the content of register A to the memory address indexed by the same binary number, and then halts execution.
This video shows SAM-80 with this program punched in memory executing it:
So, what happens here?
To convert Assembler to the machine code I use the ASM80 Online Assembler by Martin Malý, but the original Zilog Z80 Manual also conveniently provides opcodes and description in binary format.
The circuit is powered from a +5 V DC source.
The computer is very simple to build. With just two breadboards things get a little crowded. The turbo button can be implemented by replacing the original C1 capacitor with a smaller one (100 pF for 80 kHz), and adding the original 10 µF back with a switch. By default all resistors are 1 kΩ unless specified otherwise. I use bussed SIP-9 A102J resistor arrays to hook up LEDs and DIP switches – it looks much cleaner on the board.
I would strongly encourage to follow other’s advice and invest into quality breadboards, e.g. BusBoard Prototype Systems BB830T to avoid connectivity problems common with generic Chinese breadboards, like the ones I have for the RAM and the I/O. This will preserve your time and nerves. I have also got used 5114 chips off the eBay with corroded pins – took some cleaning effort to get proper signals out of them.
SAM-80 may not be the simplest of all computers, but it is definitely one of the most simple. It is basically a CPU with a little bit of memory and direct data bus I/O. It is a fun exercise in attempting to understand how computers work.
Some ideas for the next project (SAM-800):
If anyone finds this useful or will decide to build something similar, I would really love to hear your feedback.
]]>